Provided by: x11vnc_0.9.13-1.1_i386 bug

NAME

       x11vnc - allow VNC connections to real X11 displays
                version: 0.9.13, lastmod: 2011-08-10

SYNOPSIS

       x11vnc [OPTION]...

DESCRIPTION

       Typical usage is:

              Run  this  command  in  a shell on the remote machine "far-host"
              with X session you wish to view:

              x11vnc -display :0

              Then run this in another window on the machine you  are  sitting
              at:

              vncviewer far-host:0

       Once  x11vnc  establishes  connections  with  the X11 server and starts
       listening as a VNC server it will print out a string:  PORT=XXXX  where
       XXXX  is  typically 5900 (the default VNC server port).  One would next
       run something like this on the local  machine:  "vncviewer  hostname:N"
       where  "hostname"  is  the  name of the machine running x11vnc and N is
       XXXX - 5900, i.e. usually "vncviewer hostname:0".

       By default x11vnc will not allow the screen to be shared  and  it  will
       exit as soon as the client disconnects.  See -shared and -forever below
       to override these protections.  See the FAQ for details how  to  tunnel
       the  VNC  connection  through  an encrypted channel such as ssh(1).  In
       brief:

              ssh  -t  -L  5900:localhost:5900  far-host  'x11vnc   -localhost
              -display :0'

       % vncviewer -encodings 'copyrect tight zrle hextile' localhost:0

       Also,  use  of  a  VNC  password  (-rfbauth or -passwdfile) is strongly
       recommended.

       For   additional   info   see:   http://www.karlrunge.com/x11vnc/   and
       http://www.karlrunge.com/x11vnc/faq.html

       Config  file support: if the file $HOME/.x11vncrc exists then each line
       in it is treated as a single command line option.  Disable with  -norc.
       For  each option name, the leading character "-" is not required.  E.g.
       a line that is either "forever" or  "-forever"  may  be  used  and  are
       equivalent.   Likewise  "wait  100"  or  "-wait 100" are acceptable and
       equivalent lines.  The "#" character comments out to  the  end  of  the
       line  in  the  usual  way  (backslash  it  for a literal).  Leading and
       trailing whitespace is trimmed off.  Lines may be continued with a  "\"
       as the last character of a line (it becomes a space character).

OPTIONS

       -display disp

              X11  server  display  to  connect  to, usually :0.  The X server
              process must be running on same  machine  and  support  MIT-SHM.
              Equivalent to setting the DISPLAY environment variable to disp.

              See   the   description   below   of   the  "-display  WAIT:..."
              extensions, where alias "-find" will  find  the  user's  display
              automatically,  and  "-create"  will create a Xvfb session if no
              session is found.

       -auth file

              Set the X authority file to be file, equivalent to  setting  the
              XAUTHORITY environment variable to file before startup.  Same as
              -xauth file.  See Xsecurity(7) , xauth(1)  man  pages  for  more
              info.

              Use  '-auth  guess'  to  have x11vnc use its -findauth mechanism
              (described below) to try to guess the  XAUTHORITY  filename  and
              use it.

              XDM/GDM/KDM:  if you are running x11vnc as root and want to find
              the XAUTHORITY before anyone has logged into an X  session  yet,
              use:  x11vnc -env FD_XDM=1 -auth guess ...  (This will also find
              the XAUTHORITY if a user is already logged into the X  session.)
              When  running  as  root,  FD_XDM=1  will be tried if the initial
              -auth guess fails.

       -N

              If the X display is :N, try to set the VNC display to also be :N
              This  just  sets  the -rfbport option to 5900+N The program will
              exit immediately if that port is not available.  The  -N  option
              only  works  with  normal  -display  usage, e.g. :0 or :8, -N is
              ignored  in  the  -display  WAIT:...,  -create,   -find,   -svc,
              -redirect, etc modes.

       -autoport n

              Automatically  probe  for  a  free  VNC port starting at n.  The
              default is to start probing at 5900.  Use this to stay away from
              other VNC servers near 5900.

       -rfbport str

              The  VNC  port to listen on (a LibVNCServer option), e.g.  5900,
              5901, etc.  If specified as "-rfbport PROMPT"  then  the  x11vnc
              -gui is used to prompt the user to enter the port number.

       -6

              IPv6  listening  support.  In addition to IPv4, the IPv6 address
              is listened on for incoming connections.  The same  port  number
              as IPv4 is used.

              NOTE:   This  x11vnc  binary  was compiled to have the "-6" IPv6
              listening mode ENABLED by default (CPPFLAGS -DX11VNC_LISTEN6=1).
              So  to  disable  IPv6  listening mode you MUST supply the "-no6"
              option (see below.)

              The "-6"  mode  works  for  both  normal  connections  and  -ssl
              encrypted  ones.   Nearly  everything  is supported for the IPv6
              case, but there are a few exceptions.  See -stunnel for its IPv6
              support.

              Currently,  for  absolutely  everything  to  work  correctly the
              machine may need to have some IPv4 support, at the least for the
              loopback interface.  However, for nearly all usage modes no IPv4
              support is required. See -nopiv4.

              If you have trouble compiling  or  running  in  IPv6  mode,  set
              -DX11VNC_IPV6=0  in  CPPFLAGS  when  configuring to disable IPv6
              support.

       -no6

              Disable IPv6 listening support (only useful if the "-6" mode  is
              compiled   in   to   be  the  default;  see  the  X11VNC_LISTEN6
              description above under "-6".)

       -noipv6

              Do not try to use IPv6 for any listening or connecting  sockets.
              This  includes  both  the listening service port(s) and outgoing
              connections from -connect,  -connect_or_exit,  or  -proxy.   Use
              this if you are having problems due to IPv6.

       -noipv4

              Do  not try to use IPv4 for any listening or connecting sockets.
              This is mainly for  exploring  the  behavior  of  x11vnc  on  an
              IPv6-only system, but may have other uses.

       -reopen

              If  the X server connection is disconnected, try to reopen the X
              display (up to one time.)  This is of use for  display  managers
              like  GDM  (KillInitClients  option) that kill x11vnc just after
              the user logs into the X session.  Note: the reopened state  may
              be  unstable.  Set X11VNC_REOPEN_DISPLAY=n to reopen n times and
              set X11VNC_REOPEN_SLEEP_MAX to the number  of  seconds,  default
              10, to keep trying to reopen the display (once per second.)

              Update:  as  of 0.9.9, x11vnc tries to automatically avoid being
              killed by the display manager by delaying  creating  windows  or
              using    XFIXES.     So    you    shouldn't    need    to    use
              KillInitClients=false as long  as  you  log  in  quickly  enough
              (within  45  seconds  of  connecting.)   You can disable this by
              setting X11VNC_AVOID_WINDOWS=never.  You can also set it to  the
              number of seconds to delay.

       -reflect host:N

              Instead  of  connecting  to and polling an X display, connect to
              the remote VNC server host:N and be a reflector/repeater for it.
              This   is   useful  for  trying  to  manage  the  case  of  many
              simultaneous VNC viewers (e.g.  classroom  broadcasting)  where,
              e.g.  you put a repeater on each network switch, etc, to improve
              performance  by  distributing  the  load  and  network  traffic.
              Implies  -shared  (use  -noshared as a later option to disable).
              See the  discussion  below  under  -rawfb  vnc:host:N  for  more
              details.

       -id windowid

              Show  the  X  window  corresponding  to  windowid not the entire
              display.  New windows like  popup  menus,  transient  toplevels,
              etc, may not be seen or may be clipped.  Disabling SaveUnders or
              BackingStore in the X server may help  show  them.   x11vnc  may
              crash  if  the  window  is initially partially obscured, changes
              size, is iconified, etc.  Some steps are taken to avoid this and
              the -xrandr mechanism is used to track resizes.  Use xwininfo(1)
              to get the window id, or use  "-id  pick"  to  have  x11vnc  run
              xwininfo(1)  for  you  and  extract  the  id.  The -id option is
              useful for exporting very simple applications (e.g. the  current
              view on a webcam).

       -sid windowid

              As  -id,  but  instead  of using the window directly it shifts a
              root view to it: this shows SaveUnders menus, etc, although they
              will be clipped if they extend beyond the window.

       -tag str

              This  option  is  ignored,  but  allows  you to specify a unique
              string  on  the  x11vnc  command   line,   for   example   "-tag
              test34934z",  this  could  enable  a  reliable  way  to identify
              different x11vnc processes via their command lines (see ps(1)  ,
              pgrep(1) , and pkill(1) and /proc/PID/cmdline.)

       -appshare

              Simple  application  sharing  based  on  the -id/-sid mechanism.
              Every new toplevel window that the application creates induces a
              new  viewer  window  via a reverse connection.  The -id/-sid and
              -connect options are required.  Run 'x11vnc -appshare -help' for
              more info.

       -clip WxH+X+Y

              Only show the sub-region of the full display that corresponds to
              the rectangle geometry with size WxH and offset +X+Y.   The  VNC
              display has size WxH (i.e. smaller than the full display).  This
              also works for -id/-sid mode where the offset is relative to the
              upper  left  corner  of  the selected window.  An example use of
              this option would be to split a large  (e.g.  Xinerama)  display
              into  two parts to be accessed via separate viewers by running a
              separate x11vnc on each part.

              Use '-clip xinerama0' to clip to the first  xinerama  sub-screen
              (if xinerama is active).  xinerama1 for the 2nd sub-screen, etc.
              This way you don't need to figure out the WxH+X+Y of the desired
              xinerama  sub-screen.  screens are sorted in increasing distance
              from the (0,0) origin (I.e. not the Xserver's order).

       -flashcmap

              In 8bpp indexed color, let the installed colormap flash  as  the
              pointer moves from window to window (slow).  Also try the -8to24
              option to avoid flash altogether.

       -shiftcmap n

              Rare  problem,  but  some  8bpp  displays  use  less  than   256
              colorcells  (e.g. 16-color grayscale, perhaps the other bits are
              used for double buffering) *and* also need to shift  the  pixels
              values  away  from  0,  .., ncells.  n indicates the shift to be
              applied to the pixel  values.   To  see  the  pixel  values  set
              DEBUG_CMAP=1  to  print  out  a  colormap  histogram.   Example:
              -shiftcmap 240

       -notruecolor

              For 8bpp displays, force indexed color (i.e. a colormap) even if
              it looks like 8bpp TrueColor (rare problem).

       -advertise_truecolor

              If  the  X11  display is indexed color, lie to clients when they
              first connect by telling them it is  truecolor.   To  workaround
              RealVNC:    inPF    has    colourMap    but    not    8bpp   Use
              '-advertise_truecolor reset' to reset client fb too.

       -visual n

              This option probably does not do  what  you  think.   It  simply
              *forces*  the visual used for the framebuffer; this may be a bad
              thing... (e.g. messes up colors or cause a crash). It is  useful
              for  testing  and  for  some  workarounds.   n  may be a decimal
              number, or 0x hex.  Run xdpyinfo(1) for  the  values.   One  may
              also  use  "TrueColor",  etc.  see <X11/X.h> for a list.  If the
              string ends in ":m" then for better  or  for  worse  the  visual
              depth  is forced to be m.  You may want to use -noshm when using
              this option (so XGetImage may automatically translate the  pixel
              data).

       -overlay

              Handle  multiple depth visuals on one screen, e.g. 8+24 and 24+8
              overlay visuals (the 32 bits per pixel are  packed  with  8  for
              PseudoColor and 24 for TrueColor).

              Currently  -overlay  only works on Solaris via XReadScreen(3X11)
              and IRIX using XReadDisplay(3).  On Solaris there is  a  problem
              with  image "bleeding" around transient popup menus (but not for
              the menu itself): a  workaround  is  to  disable  SaveUnders  by
              passing the "-su" argument to Xsun (in /etc/dt/config/Xservers).

              Use  -overlay  as  a  workaround for situations like these: Some
              legacy applications  require  the  default  visual  to  be  8bpp
              (8+24),  or they will use 8bpp PseudoColor even when the default
              visual is depth 24 TrueColor (24+8).  In these cases  colors  in
              some  windows  will  be  incorrect  in x11vnc unless -overlay is
              used.  Another use of -overlay is to enable  showing  the  exact
              mouse cursor shape (details below).

              Under  -overlay,  performance will be somewhat slower due to the
              extra image transformations required.  For  optimal  performance
              do  not  use -overlay, but rather configure the X server so that
              the default visual is depth 24 TrueColor and  try  to  have  all
              apps  use  that  visual  (e.g.  some apps have -use24 or -visual
              options).

       -overlay_nocursor

              Sets -overlay, but does not try to draw the exact  mouse  cursor
              shape using the overlay mechanism.

       -8to24 [opts]

              Try this option if -overlay is not supported on your OS, and you
              have a legacy 8bpp app that you want to view  on  a  multi-depth
              display  with default depth 24 (and is 32 bpp) OR have a default
              depth 8 display with depth 24 overlay  windows  for  some  apps.
              This  option  may not work on all X servers and hardware (tested
              on XFree86/Xorg mga driver and Xsun).  The "opts" string is  not
              required and is described below.

              This  mode enables a hack where x11vnc monitors windows within 3
              levels from the root window.  If it finds any that are  8bpp  it
              extracts  the  indexed  color pixel values using XGetImage() and
              then applies a transformation using the  colormap(s)  to  create
              TrueColor  RGB  values that it in turn inserts into bits 1-24 of
              the framebuffer.  This creates a depth 24 "view" of the  display
              that is then exported via VNC.

              Conversely,  for  default depth 8 displays, the depth 24 regions
              are read  by  XGetImage()  and  everything  is  transformed  and
              inserted into a depth 24 TrueColor framebuffer.

              Note  that  even  if  there are *no* depth 24 visuals or windows
              (i.e. pure 8bpp), this mode is potentially an  improvement  over
              -flashcmap  because it avoids the flashing and shows each window
              in the correct color.

              This method works OK, but may still have bugs and  it  does  hog
              resources.   If  there are multiple 8bpp windows using different
              colormaps, one may have to iconify all but one for the colors to
              be correct.

              There  may be painting errors for clipping and switching between
              windows of depths 8 and 24.  Heuristics are applied  to  try  to
              minimize the painting errors.  One can also press 3 Alt_L's in a
              row to refresh the screen if the error does not  repair  itself.
              Also the option -fixscreen 8=3.0 or -fixscreen V=3.0 may be used
              to periodically refresh the screen  at  the  cost  of  bandwidth
              (every 3 sec for this example).

              The  [opts] string can contain the following settings.  Multiple
              settings are separated by commas.

              For for some X servers with default depth 24 a  speedup  may  be
              achieved  via  the  option  "nogetimage".  This enables a scheme
              were  XGetImage()  is  not  used  to  retrieve  the  8bpp  data.
              Instead,  it  assumes that the 8bpp data is in bits 25-32 of the
              32bit X pixels.  There is  no  requirement  that  the  X  server
              should put the data there for our poll requests, but some do and
              so the extra steps to retrieve it can be skipped.   Tested  with
              mga driver with XFree86/Xorg.  For the default depth 8 case this
              option is ignored.

              To adjust how often XGetImage() is used to poll the  non-default
              visual regions for changes, use the option "poll=t" where "t" is
              a floating point time.  (default: 0.05)

              Setting the option "level2"  will  limit  the  search  for  non-
              default  visual  windows to two levels from the root window.  Do
              this on slow machines where you know  the  window  manager  only
              imposes  one  extra  window  between the app window and the root
              window.

              Also for very slow  machines  use  "cachewin=t"  where  t  is  a
              floating  point  amount  of  time  to cache XGetWindowAttributes
              results.  E.g. cachewin=5.0.  This may lead to the windows being
              unnoticed  for  this  amount of time when deiconifying, painting
              errors, etc.

              While testing on a very old SS20 these  options  gave  tolerable
              response:   -8to24   poll=0.2,cachewin=5.0.   For  this  machine
              -overlay is supported and gives better response.

              Debugging for this mode  can  be  enabled  by  setting  "dbg=1",
              "dbg=2", or "dbg=3".

       -24to32

              Very  rare  problem: if the framebuffer (X display or -rawfb) is
              24bpp instead of the usual 32bpp, then dynamically transform the
              pixels  to  32bpp.  This will be slower, but can be used to work
              around problems where VNC  viewers  cannot  handle  24bpp  (e.g.
              "main:  setPF:  not  8,  16  or 32 bpp?").  See the FAQ for more
              info.

              In the case of -rawfb mode, the pixels are directly modified  by
              inserting  a 0 byte to pad them out to 32bpp.  For X displays, a
              kludge  is  done  that  is   equivalent   to   "-noshm   -visual
              TrueColor:32".  (If better performance is needed for the latter,
              feel free to ask).

       -scale fraction

              Scale the framebuffer by factor fraction.  Values  less  than  1
              shrink the fb, larger ones expand it. Note: the image may not be
              sharp and response  may  be  slower.   If  fraction  contains  a
              decimal  point  "."  it  is  taken  as  a floating point number,
              alternatively the notation "m/n" may be used to denote fractions
              exactly, e.g. -scale 2/3

              To   scale   asymmetrically   in  the  horizontal  and  vertical
              directions, specify a WxH geometry to stretch to:  e.g.  '-scale
              1024x768', or also '-scale 0.9x0.75'

              Scaling  Options: can be added after fraction via ":", to supply
              multiple ":" options use commas.  If  you  just  want  a  quick,
              rough  scaling  without blending, append ":nb" to fraction (e.g.
              -scale 1/3:nb).  No blending is the  default  for  8bpp  indexed
              color, to force blending for this case use ":fb".

              To  disable  -scrollcopyrect  and -wirecopyrect under -scale use
              ":nocr".  If you need to to enable them  use  ":cr"  or  specify
              them  explicitly  on  the  command  line.   If  a  slow  link is
              detected, ":nocr" may be applied automatically.  Default: :cr

              More esoteric options: for  compatibility  with  vncviewers  the
              scaled  width is adjusted to be a multiple of 4: to disable this
              use ":n4".  ":in" use interpolation scheme even when  shrinking,
              ":pad"  pad  scaled  width and height to be multiples of scaling
              denominator (e.g. 3 for 2/3).

       -geometry WxH

              Same as -scale WxH

       -scale_cursor frac

              By default if -scale is supplied the cursor shape is  scaled  by
              the same factor.  Depending on your usage, you may want to scale
              the cursor independently of the screen or not at  all.   If  you
              specify  -scale_cursor the cursor will be scaled by that factor.
              When using -scale mode to keep the cursor at its "natural"  size
              use  "-scale_cursor  1".   Most of the ":" scaling options apply
              here as well.

       -viewonly

              All VNC clients can only watch (default off).

       -shared

              VNC display is shared, i.e. more than one viewer can connect  at
              the same time (default off).

       -once

              Exit  after the first successfully connected viewer disconnects,
              opposite of -forever. This is the Default.

       -forever

              Keep listening for more connections rather than exiting as  soon
              as the first client(s) disconnect. Same as -many

              To get the standard non-shared VNC behavior where when a new VNC
              client  connects  the  existing  VNC  client  is  dropped   use:
              -nevershared  -forever    This  method can also be used to guard
              against hung TCP connections that do not go away.

       -loop

              Create an outer loop restarting the x11vnc process  whenever  it
              terminates.   -bg  and  -inetd are ignored in this mode (however
              see -loopbg below).

              Useful for continuing  even  if  the  X  server  terminates  and
              restarts  (at  that  moment  the process will need permission to
              reconnect to the new X server of course).

              Use, e.g., -loop100 to sleep  100  millisecs  between  restarts,
              etc.   Default  is  2000ms (i.e. 2 secs) Use, e.g. -loop300,5 to
              sleep 300 ms and only loop 5 times.

              If -loopbg (plus any numbers) is specified  instead,  the  "-bg"
              option  is  implied  and the mode approximates inetd(8) usage to
              some degree.  In this case when it goes into the background  any
              listening  sockets  (i.e.  ports  5900, 5800) are closed, so the
              next one in the loop can use them.  This mode will  only  be  of
              use  if  a  VNC  client  (the  only  client for that process) is
              already connected before the process goes into  the  background,
              for  example,  usage of -display WAIT:.., -svc, and -connect can
              make use of this "poor man's" inetd mode.  The default wait time
              is  500ms  in this mode.  This usage could use useful:  -svc -bg
              -loopbg

       -timeout n

              Exit unless a client connects within the first n  seconds  after
              startup.

              If there have been no connection attempts after n seconds x11vnc
              exits immediately.  If a client is trying to connect but has not
              progressed  to the normal operating state, x11vnc gives it a few
              more seconds to finish and exits if it does not make it  to  the
              normal state.

              For  reverse  connections  via  -connect  or  -connect_or_exit a
              timeout of n seconds will be set for all reverse  connects.   If
              the   connect   timeout   alarm   goes  off,  x11vnc  will  exit
              immediately.

       -sleepin n

              At startup sleep n seconds  before  proceeding  (e.g.  to  allow
              redirs and listening clients to start up)

              If  a range is given: '-sleepin min-max', a random value between
              min and max is slept. E.g. '-sleepin 0-20' and ´-sleepin 10-30'.
              Floats are allowed too.

       -inetd

              Launched  by inetd(8): stdio instead of listening socket.  Note:
              if you are not redirecting stderr to a log file (via shell 2> or
              -o  option)  you  MUST also specify the -q option, otherwise the
              stderr goes  to  the  viewer  which  will  cause  it  to  abort.
              Specifying both -inetd and -q and no -o will automatically close
              the stderr.

              If the libvncserver used supports non AF_INET sockets  (the  one
              bundled  in  x11vnc 0.9.13 and later does), then -inetd mode can
              be used for a raw stdio  pipe.  For  example,  using  the  SSVNC
              viewer exec=... mechanism:

              ssvnc  -viewer  exec="ssh -tt -e none user@host \ ´x11vnc -inetd
              -o log.txt -display :0'"

              where the long cmdline has been split.  In the  above  the  only
              TCP  connection is that of the ssh connection.  There is no port
              redirection (-L), etc.; raw stdio is used on both sides  of  the
              ssh.  In some cases the -tt option is not needed.

       -tightfilexfer

              Enable the TightVNC file transfer extension. Note that that when
              the  -viewonly  option  is  supplied  all  file  transfers   are
              disabled.   Also  clients  that  log in viewonly cannot transfer
              files.  However, if the remote  control  mechanism  is  used  to
              change  the global or per-client viewonly state the filetransfer
              permissions will NOT change.

              IMPORTANT: please understand if -tightfilexfer is specified  and
              you  run x11vnc as root for, say, inetd or display manager (gdm,
              kdm, ...) access and you do not have it  switch  users  via  the
              -users  option,  then  VNC  Viewers  that connect are able to do
              filetransfer reads and writes as *root*.

              Also, tightfilexfer is disabled in -unixpw mode.

       -ultrafilexfer

              Note: to enable UltraVNC filetransfer and to get it to work  you
              probably need to supply these LibVNCServer options: "-rfbversion
              3.6 -permitfiletransfer" "-ultrafilexfer" is an alias  for  this
              combination.

              IMPORTANT:  please understand if -ultrafilexfer is specified and
              you run x11vnc as root for, say, inetd or display manager  (gdm,
              kdm,  ...)  access  and  you do not have it switch users via the
              -users option, then VNC Viewers that  connect  are  able  to  do
              filetransfer reads and writes as *root*.

              Note   that   sadly   you  cannot  do  both  -tightfilexfer  and
              -ultrafilexfer at the same  time  because  the  latter  requires
              setting the version to 3.6 and tightvnc will not do filetransfer
              when it sees that version number.

       -http

              Instead of using -httpdir (see below) to specify where the  Java
              vncviewer  applet  is,  have  x11vnc  try  to  *guess* where the
              directory is by looking relative to the program location and  in
              standard   locations   (/usr/local/share/x11vnc/classes,   etc).
              Under -ssl or -stunnel the ssl classes subdirectory is sought.

       -http_ssl

              As -http, but force lookup for ssl classes subdir.

              Note that for HTTPS, single-port Java applet  delivery  you  can
              set X11VNC_HTTPS_DOWNLOAD_WAIT_TIME to the max number of seconds
              to wait for the applet download to finish.  The default is 15.

       -avahi

              Use the Avahi/mDNS  ZeroConf  protocol  to  advertise  this  VNC
              server   to  the  local  network.  (Related  terms:  Rendezvous,
              Bonjour).  Depending on your setup, you may need to start avahi-
              daemon and open udp port 5353 in your firewall.

              You   can   set   X11VNC_AVAHI_NAME,  X11VNC_AVAHI_HOST,  and/or
              X11VNC_AVAHI_PORT environment variables to override the  default
              values.  For example: -env X11VNC_AVAHI_NAME=wally

              If the avahi API cannot be found at build time, a helper program
              like avahi- publish(1) or dns- sd(1) will be tried

       -mdns

              Same as -avahi.

       -zeroconf

              Same as -avahi.

       -connect string

              For use with "vncviewer -listen" reverse connections.  If string
              has  the  form "host" or "host:port" the connection is made once
              at startup.

              Use commas for a list of host's and host:port's.  E.g.  -connect
              host1,host2 or host1:0,host2:5678.  Note that to reverse connect
              to multiple hosts at the same time you will likely need to  also
              supply: -shared

              Note  that  unlike  most  vnc  servers,  x11vnc  will  require a
              password  for  reverse  as  well  as  for  forward  connections.
              (provided  password auth has been enabled, -rfbauth, etc) If you
              do not want to require a password for  reverse  connections  set
              X11VNC_REVERSE_CONNECTION_NO_AUTH=1  in  your environment before
              starting x11vnc.

              If string contains "/" it is instead interpreted as  a  file  to
              periodically  check  for  new hosts.  The first line is read and
              then the file is truncated.  Be careful about  the  location  of
              this file if x11vnc is running as root (e.g. via gdm(1) , etc).

              Repeater  mode:  Some  services  provide  an  intermediate  "vnc
              repeater":  http://www.uvnc.com/addons/repeater.html  (and  also
              http://koti.mbnet.fi/jtko/  for  linux  port)  that  acts  as  a
              proxy/gateway.  Modes like these require an initial string to be
              sent  for  the  reverse  connection  before  the VNC protocol is
              started.  Here are the ways to do this:

              -connect           pre=some_string+host:port            -connect
              pre128=some_string+host:port -connect repeater=ID:1234+host:port
              -connect repeater=23.45.67.89::5501+host:port

              SSVNC notation is also supported:

              -connect repeater://host:port+ID:1234

              As with normal -connect usage,  if  the  repeater  port  is  not
              supplied 5500 is assumed.

              The  basic  idea is between the special tag, e.g. "pre=" and "+"
              is the pre-string to be sent.  Note that in this case  host:port
              is  the  repeater  server, NOT the vnc viewer.  Somehow the pre-
              string tells the repeater server how to find the vnc viewer  and
              connect you to it.

              In  the  case pre=some_string+host:port, "some_string" is simply
              sent. In the case preNNN=some_string+host:port "some_string"  is
              sent  in  a  null padded buffer of length NNN.  repeater= is the
              same as pre250=, this is the ultravnc repeater buffer size.

              Strings like "\n" and "\r", etc. are  expanded  to  newline  and
              carriage  return.   "\c"  is  expanded  to "," since the connect
              string is comma separated.

              See also the -proxy option below for additional  ways  to  plumb
              reverse connections.

              Reverse  SSL: using -connect in -ssl mode makes x11vnc act as an
              SSL client (initiates SSL connection) rather than an SSL server.
              The  idea is x11vnc might be connecting to stunnel on the viewer
              side with the viewer in listening mode.  If you do not want this
              behavior,  use -env X11VNC_DISABLE_SSL_CLIENT_MODE=1.  With this
              the viewer side can act as the SSL client as  it  normally  does
              for forward connections.

              Reverse SSL Repeater mode:  This will work, but note that if the
              VNC Client does  any  sort  of  a  'Fetch  Cert'  action  before
              connecting,  then  the  Repeater will likely drop the connection
              and both sides will  need  to  restart.   Consider  the  use  of
              -connect_or_exit and -loop300,2 to have x11vnc reconnect once to
              the repeater after the fetch.  You will probably  also  want  to
              supply  -sslonly  to avoid x11vnc thinking the delay in response
              means   the   connection   is    VeNCrypt.     The    env    var
              X11VNC_DISABLE_SSL_CLIENT_MODE=1  discussed  above  may  also be
              useful (i.e. the viewer  can  do  a  forward  connection  as  it
              normally does.)

              IPv6:  as of x11vnc 0.9.10 the -connect option should connect to
              IPv6 hosts properly.  If there are problems you can disable IPv6
              by  setting  -DX11VNC_IPV6=0  in  CPPFLAGS when configuring.  If
              there problems connecting to IPv6 hosts consider  a  relay  like
              the included inet6to4 script or the -proxy option.

       -connect_or_exit str

              As  with  -connect,  except  if  none of the reverse connections
              succeed, then x11vnc shuts down immediately

              An easier to type alias for this option is '-coe'

              By the way, if you do not want x11vnc to listen on ANY interface
              use -rfbport 0  which is handy for the -connect_or_exit mode.

       -proxy string

              Use  proxy  in  string  (e.g.  host:port)  as a proxy for making
              reverse connections (-connect or -connect_or_exit options).

              Web proxies are supported, but note by default most of them only
              support  destination  connections  to  ports 443 or 563, so this
              might not be very useful (the viewer would  need  to  listen  on
              that port or the router would have to do a port redirection).

              A   web   proxy  may  be  specified  by  either  "host:port"  or
              "http://host:port" (the port is  required  even  if  it  is  the
              common choices 80 or 8080)

              SOCKS4,  SOCKS4a,  and SOCKS5 are also supported.  SOCKS proxies
              normally do  not  have  restrictions  on  the  destination  port
              number.

              Use a format like this: socks://host:port or socks5://host:port.
              Note that ssh -D does not support  SOCKS4a,  so  use  socks5://.
              For  socks://  SOCKS4 is used on a numerical IP and "localhost",
              otherwise SOCKS4a is used (and so the proxy tries to do the  DNS
              lookup).

              An  experimental mode is "-proxy http://host:port/..."  Note the
              "/" after the port that  distinguishes  it  from  a  normal  web
              proxy.   The port must be supplied even if it is the default 80.
              For this mode a GET is done to the supplied URL with the  string
              host=H&port=P  appended.   H  and P will be the -connect reverse
              connect host and port.  Use the string "__END__" to disable  the
              appending.   The  basic  idea here is that maybe some cgi script
              provides the  actual  viewer  hookup  and  tunnelling.   How  to
              actually  achieve  this within cgi, php, etc. is not clear...  A
              custom web server or apache module would be straight-forward.

              Another experimental mode is "-proxy ssh://user@host"  in  which
              case  a  SSH  tunnel  is  used for the proxying.  "user@" is not
              needed unless your unix username is different on "host".  For  a
              non-standard  SSH port use ssh://user@host:port.  If proxies are
              chained (see next paragraph) then the ssh one must be the  first
              one.  If ssh-agent is not active, then the ssh password needs to
              be entered in the terminal where x11vnc is running.  Examples:

              -connect localhost:0 -proxy ssh://me@friends-pc:2222

              -connect snoopy:0 -proxy ssh://ssh.company.com

              Multiple proxies may be chained together in case  one  needs  to
              ricochet  off  of  a  number  of  hosts to finally reach the VNC
              viewer.  Up to 3 may be chained, separate them by commas in  the
              order     they     are    to    be    connected    to.     E.g.:
              http://host1:port1,socks5://host2:port2    or    three     like:
              first,second,third

              IPv6:  as  of  x11vnc 0.9.10 the -proxy option should connect to
              IPv6 hosts properly.  If there are problems you can disable IPv6
              by  setting  -DX11VNC_IPV6=0  in  CPPFLAGS when configuring.  If
              there problems connecting to IPv6 hosts consider  a  relay  like
              the included inet6to4 script.

       -vncconnect, -novncconnect

              Monitor  the  VNC_CONNECT  X  property  set  by the standard VNC
              program vncconnect(1).  When the property is set  to  "host"  or
              "host:port"  establish  a  reverse  connection.   Using xprop(1)
              instead of vncconnect may  work  (see  the  FAQ).   The  -remote
              control  mechanism  uses  X11VNC_REMOTE channel, and this option
              disables/enables it as well.  Default: -vncconnect

              To use different names for these X11 properties  (e.g.  to  have
              separate  communication  channels  for  multiple x11vnc's on the
              same display) set the VNC_CONNECT or X11VNC_REMOTE env. vars. to
              the      string      you     want,     for     example:     -env
              X11VNC_REMOTE=X11VNC_REMOTE_12345 Both sides of the channel must
              use the same unique name.  The same can be done for the internal
              X11VNC_TICKER property (heartbeat and timestamp) if desired.

       -allow host1[,host2..]

              Only allow client connections  from  hosts  matching  the  comma
              separated  list  of  hostnames  or IP addresses.  By ending in a
              ".", it can also be a numerical IP prefix,  e.g.  "192.168.100."
              to  match  a  simple subnet, for more control build LibVNCServer
              with libwrap support (See the FAQ).  If the list contains a  "/"
              it  instead  is  a interpreted as a file containing addresses or
              prefixes that is re-read each time a new client connects.  Lines
              can be commented out with the "#" character in the usual way.

              -allow applies in -ssl mode, but not in -stunnel mode.

              IPv6:  as  of  x11vnc  0.9.10  a  host  can be specified in IPv6
              numerical format, e.g. 2001:4860:b009::93

              Env. vars: Set -env X11VNC_DEBUG_ACCESS=1 to print out debugging
              info    during    the    check_access()    call.     Set    -env
              X11VNC_ALLOW_FULLMATCH=1 to force a full string match, that  is,
              no subnet "." matching will be performed.

              Unix  sockets:  if -unixsock is being used and you want to limit
              TCP access also you must also  include  the  path  to  the  unix
              socket  prefixed  with  "unix="  in the allow list, e.g.: -allow
              192.168.100.3,unix=/tmp/mysock If the socket is not a named one,
              e.g. created via socketpair(2) with -inetd, then you must supply
              the   generic   name   x11vnc   gives   to   it,   e.g.   -allow
              192.168.100.3,UNNAMED_AF_UNIX  In both cases it must be an exact
              string match to be allowed to  connect.   Note  that  since  you
              completely  control  these  local non-TCP access methods by file
              system permissions, etc., it is not useful to guard against them
              with  -allow,  however  you still need to have them in the allow
              list to let them connect.

       -localhost

              Basically the same as "-allow 127.0.0.1".

              Note: if you want to restrict  which  network  interface  x11vnc
              listens  on,  see  the  -listen  option  below.   E.g.  "-listen
              localhost" or "-listen 192.168.3.21".  As a  special  case,  the
              option "-localhost" implies "-listen localhost".

              A rare case, but for non-localhost -listen usage, if you use the
              remote control mechanism (-R) to change  the  -listen  interface
              you may need to manually adjust the -allow list (and vice versa)
              to avoid situations where  no  connections  (or  too  many)  are
              allowed.

              If  you  do  not  want  x11vnc  to  listen  on ANY TCP interface
              (evidently you are using -connect or -connect_or_exit,  or  plan
              to  use  remote  control: -R connect:host, or to use -unixsock),
              specify -rfbport 0

              IPv6: if IPv6 is supported, this  option  automatically  implies
              the IPv6 loopback address '::1' as well.

       -unixsock str

              In  addition  to the regular TCP port, listen on the unix socket
              (AF_UNIX) 'str' for incoming  connections.   This  mode  is  for
              either  local  connections  or a tunnel endpoint where one wants
              the file permission of the unix socket file  to  determine  what
              can  connect  to  it.  Example: mkdir ~/s; chmod 700 ~/s; x11vnc
              -unixsock  ~/s/mysock  -rfbport   0   ...    same   as:   x11vnc
              -unixsockonly ~/s/mysock ...  (see -unixsockonly below.)

              This  mode  currently requires the modified libvncserver bundled
              in the the x11vnc 0.9.13 tarball and later.

              Note that the SSVNC unix vncviewer can connect to unix  sockets,
              for example: ssvnc -viewer unix=./s/mysock

              As  a  special  mechanism,  if  'str'  for  either  -unixsock or
              -unixsockonly is of the form "fd=n" where n  is  a  non-negative
              decimal  integer,  then  instead of creating a unix socket, that
              file descriptor (assumed already  opened  and  O_RDWR)  will  be
              attached as a VNC client.  Perhaps the program that execs x11vnc
              has created a  socketpair(2)  to  communicate  over.   Use  this
              mechanism  if  -inetd  (which is basically fd=0) is not flexible
              enough for you.

       -unixsockonly str

              Listen on unix socket 'str' only, no TCP ports. First note  that
              one  can disable all tcp listening ports by specifying '-rfbport
              0'. The option '-unixsockonly str' is functionally equivalent to
              '-unixsock str -rfbport 0'

       -listen6 str

              When  in  IPv6  listen  mode  "-6",  listen  only on the network
              interface with address  str.   It  also  works  for  link  scope
              addresses   (fe80::219:dbff:fee5:3f92%eth0)  and  IPv6  hostname
              strings (e.g. ipv6.google.com.)  Use LibVNCServer -listen option
              for the IPv4 interface.

       -nolookup

              Do  not  use  gethostbyname() or gethostbyaddr() to look up host
              names or IP numbers.  Use this if name resolution is incorrectly
              set up and leads to long pauses as name lookups time out, etc.

       -input string

              Fine tuning of allowed user input.  If string does not contain a
              comma "," the tuning applies only to normal clients.   Otherwise
              the part before "," is for normal clients and the part after for
              view-only clients.  "K" is for Keystroke input, "M"  for  Mouse-
              motion  input,  "B" for Button-click input, "C" is for Clipboard
              input, and "F" is for  File  transfer  (ultravnc  only).   Their
              presence in the string enables that type of input.  E.g. "-input
              M" means normal users can  only  move  the  mouse  and   "-input
              KMBCF,M"  lets  normal  users  do anything and enables view-only
              users to move the mouse.  This option is ignored when  a  global
              -viewonly is in effect (all input is discarded in that case).

       -grabkbd

              When VNC viewers are connected, attempt to the grab the keyboard
              so a (non-malicious) user sitting at the physical display is not
              able  to enter keystrokes.  This method uses XGrabKeyboard(3X11)
              and so it is not secure and does not rule out the person at  the
              physical  display  injecting  keystrokes  by flooding the server
              with them, grabbing the keyboard himself, etc.  Some  degree  of
              cooperation  from the person at the display is assumed.  This is
              intended for remote help-desk or educational usage modes.

              Note: on  some  recent  (12/2010)  X  servers  and/or  desktops,
              -grabkbd  no  longer  works: it prevents the window manager from
              resizing windows and  similar  things.   Try  -ungrabboth  below
              (might not work.)

       -grabptr

              As -grabkbd, but for the mouse pointer using XGrabPointer(3X11).
              Unfortunately due to the way the X server works, the  mouse  can
              still  be  moved around by the user at the physical display, but
              he will not be able to change window focus with it.   Also  some
              window  managers  that  call XGrabServer(3X11) for resizes, etc,
              will act on the local  user's  input.   Again,  some  degree  of
              cooperation from the person at the display is assumed.

       -ungrabboth

              Whenever there is any input (either keyboard or pointer), ungrab
              *both*  the  keyboard  and  the  pointer  while  injecting   the
              synthetic  input.   This  is  to  allow  window managers, etc. a
              chance to grab.

       -grabalways

              Apply both -grabkbd and -grabptr even when no  VNC  viewers  are
              connected.   If  you  only  want  one of them, use the -R remote
              control to turn the other back on, e.g. -R nograbptr.

              (PASSWORDS:  Note  that  the   LibVNCServer   password   options
              "-rfbauth file" and "-passwd str" are described at the bottom of
              the help output.)

       -viewpasswd string

              Supply a 2nd password for view-only logins.  The -passwd  (full-
              access) password must also be supplied.

       -passwdfile filename

              Specify the LibVNCServer password via the first line of the file
              filename (instead of via  -passwd  on  the  command  line  where
              others might see it via ps(1) ).

              See the descriptions below for how to supply multiple passwords,
              view-only  passwords,  to  specify  external  programs  for  the
              authentication, and other features.

              If  the filename is prefixed with "rm:" it will be removed after
              being read.  Perhaps this is useful in limiting the  readability
              of  the  file.   In  general,  the  password  file should not be
              readable  by  untrusted  users  (BTW:  neither  should  the  VNC
              -rfbauth  file:  it is NOT encrypted, only obscured with a fixed
              key).

              If the filename is prefixed with "read:" it will periodically be
              checked  for  changes and reread.  It is guaranteed to be reread
              just when a new client connects so  that  the  latest  passwords
              will be used.

              If  filename  is  prefixed with "cmd:" then the string after the
              ":" is run as an external command: the  output  of  the  command
              will be interpreted as if it were read from a password file (see
              below).  If the command  does  not  exit  with  0,  then  x11vnc
              terminates  immediately.   To  specify  more than 1000 passwords
              this way set X11VNC_MAX_PASSWDS  before  starting  x11vnc.   The
              environment variables are set as in -accept.

              Note that due to the VNC protocol only the first 8 characters of
              a password are used (DES key).

              If filename is prefixed with "custom:" then  a  custom  password
              checker  is  supplied  as an external command following the ":".
              The command will be run when a  client  authenticates.   If  the
              command  exits  with  0  the client is accepted, otherwise it is
              rejected.  The environment variables are set as in -accept.

              The standard input to the custom command will be a decimal digit
              "len"  followed by a newline. "len" specifies the challenge size
              and is usually 16 (the VNC spec).  Then follows len bytes  which
              is the random challenge string that was sent to the client. This
              is then followed by len more bytes holding the client's response
              (i.e.  the  challenge  string  encrypted  via  DES with the user
              password in the standard situation).

              The  "custom:"  scheme  can  be  useful  to  implement   dynamic
              passwords  or to implement methods where longer passwords and/or
              different encryption  algorithms  are  used.   The  latter  will
              require customizing the VNC client as well.  One could create an
              MD5SUM based scheme for example.  See also -unixpw_cmd below.

              File format for -passwdfile:

              If multiple non-blank lines exist in the file they are all taken
              as  valid  passwords.   Blank lines are ignored.  Password lines
              may  be  "commented  out"  (ignored)  if  they  begin  with  the
              character "#" or the line contains the string "__SKIP__".  Lines
              may be annotated by use of the "__COMM__" string: from it to the
              end  of the line is ignored.  An empty password may be specified
              via the "__EMPTY__" string on a line by itself (note your viewer
              might not accept empty passwords).

              If  the string "__BEGIN_VIEWONLY__" appears on a line by itself,
              the remaining passwords  are  used  for  viewonly  access.   For
              compatibility,  as  a special case if the file contains only two
              password lines  the  2nd  one  is  automatically  taken  as  the
              viewonly  password.   Otherwise  the  "__BEGIN_VIEWONLY__" token
              must be used to have viewonly passwords.  (tip: make the 3rd and
              last   line   be  "__BEGIN_VIEWONLY__"  to  have  2  full-access
              passwords)

       -showrfbauth filename

              Print to the screen  the  obscured  VNC  password  kept  in  the
              rfbauth file filename and then exit.

       -usepw

              If  no  other  password method was supplied on the command line,
              first look for ~/.vnc/passwd and if found use it with  -rfbauth;
              next,  look  for  ~/.vnc/passwdfile and use it with -passwdfile;
              otherwise,  prompt  the  user   for   a   password   to   create
              ~/.vnc/passwd  and  use it with the -rfbauth option.  If none of
              these succeed x11vnc exits immediately.

       -storepasswd pass file

              Store password pass as the VNC password in the file file.   Once
              the  password is stored the program exits.  Use the password via
              "-rfbauth file"

              If called with no arguments, "x11vnc -storepasswd", the user  is
              prompted   for   a  password  and  it  is  stored  in  the  file
              ~/.vnc/passwd.  Called with one argument, that will be the  file
              to store the prompted password in.

       -nopw

              Disable the big warning message when you use x11vnc without some
              sort of password.

       -accept string

              Run a command (possibly to prompt the user at the  X11  display)
              to  decide  whether  an  incoming  client  should  be allowed to
              connect or not.  string is an external command run via system(3)
              or  some special cases described below.  Be sure to quote string
              if it contains spaces, shell characters, etc.  If  the  external
              command  returns  0 the client is accepted, otherwise the client
              is rejected.  See below for an  extension  to  accept  a  client
              view-only.

              If  x11vnc is running as root (say from inetd(8) or from display
              managers xdm(1) ,  gdm(1)  ,  etc),  think  about  the  security
              implications  carefully  before  supplying this option (likewise
              for the -gone option).

              Environment: The RFB_CLIENT_IP environment variable will be  set
              to the incoming client IP number and the port in RFB_CLIENT_PORT
              (or  -1   if   unavailable).    Similarly,   RFB_SERVER_IP   and
              RFB_SERVER_PORT  (the x11vnc side of the connection), are set to
              allow identification of the tcp  virtual  circuit.   The  x11vnc
              process  id  will  be  in  RFB_X11VNC_PID, a client id number in
              RFB_CLIENT_ID, and the number  of  other  connected  clients  in
              RFB_CLIENT_COUNT.  RFB_MODE will be "accept".  RFB_STATE will be
              PROTOCOL_VERSION, SECURITY_TYPE, AUTHENTICATION, INITIALISATION,
              NORMAL,  or  UNKNOWN indicating up to which state the client has
              achieved.  RFB_LOGIN_VIEWONLY will be 0,  1,  or  -1  (unknown).
              RFB_USERNAME,  RFB_LOGIN_TIME,  and RFB_CURRENT_TIME may also be
              set.

              If string is "popup" then a builtin popup window is  used.   The
              popup  will  time out after 120 seconds, use "popup:N" to modify
              the timeout to N seconds (use 0 for no timeout).

              In the case of "popup" and when the -unixpw option is specified,
              then  a  *second*  window  will  be  popped  up  after  the user
              successfully logs in via his UNIX password.  This time the  user
              will be identified as UNIX:username@hostname, the "UNIX:" prefix
              indicates which user the viewer  logged  as  via  -unixpw.   The
              first  popup  is  only for whether to allow him to even *try* to
              login via unix password.

              If string is "xmessage" then an xmessage(1) invocation  is  used
              for  the command.  xmessage must be installed on the machine for
              this to work.

              Both "popup" and "xmessage" will present an option for accepting
              the client "View-Only" (the client can only watch).  This option
              will not be presented if -viewonly has been specified, in  which
              case the entire display is view only.

              If  the  user  supplied  command is prefixed with something like
              "yes:0,no:*,view:3  mycommand  ..."  then  this  associates  the
              numerical  command return code with the actions: accept, reject,
              and accept-view-only, respectively.  Use "*" instead of a number
              to  indicate  the default action (in case the command returns an
              unexpected value).  E.g. "no:*" is a good choice.

              Note that x11vnc blocks while the external command or  popup  is
              running  (other  clients may see no updates during this period).
              So a person sitting a the physical display is needed to  respond
              to an popup prompt. (use a 2nd x11vnc if you lock yourself out).

              More -accept tricks: use "popupmouse" to only allow mouse clicks
              in the builtin popup to be recognized.  Similarly use "popupkey"
              to  only recognize keystroke responses.  These are to help avoid
              the user accidentally accepting a client by typing or  clicking.
              All  3 of the popup keywords can be followed by +N+M to supply a
              position for the popup window.  The default  is  to  center  the
              popup window.

       -afteraccept string

              As -accept, except to run a user supplied command after a client
              has been accepted and authenticated. RFB_MODE  will  be  set  to
              "afteraccept"  and  the other RFB_* variables are as in -accept.
              Unlike -accept, the command return code is  not  interpreted  by
              x11vnc.  Example: -afteraccept 'killall xlock &'

       -gone string

              As  -accept, except to run a user supplied command when a client
              goes away (disconnects).  RFB_MODE will be set to "gone" and the
              other  RFB_*  variables  are as in -accept.  The "popup" actions
              apply as well.  Unlike -accept, the command return code  is  not
              interpreted by x11vnc.  Example: -gone 'xlock &'

       -unixpw [list]

              Use  Unix username and password authentication.  x11vnc will use
              the su(1) program to verify the user's password.  [list]  is  an
              optional comma separated list of allowed Unix usernames.  If the
              [list] string begins with the character "!" then the entire list
              is  taken  as  an  exclude list.  See below for per-user options
              that can be applied.

              A familiar "login:" and "Password:" dialog is presented  to  the
              user  on a black screen inside the vncviewer.  The connection is
              dropped if the user fails to supply the correct  password  in  3
              tries or does not send one before a 45 second timeout.  Existing
              clients are view-only during this period.

              If the first  character  received  is  "Escape"  then  the  unix
              username  will  not  be displayed after "login:" as it is typed.
              This could be of use for VNC viewers that automatically type the
              username and password.

              Since  the detailed behavior of su(1) can vary from OS to OS and
              for local configurations, test the  mode  before  deployment  to
              make  sure  it  is  working properly.  x11vnc will attempt to be
              conservative and reject a login if anything abnormal occurs.

              One case to note: FreeBSD and the other BSD's by default  it  is
              impossible  for  the  user  running x11vnc to validate his *own*
              password via su(1) (commenting  out  the  pam_self.so  entry  in
              /etc/pam.d/su  eliminates  this  behavior).  So the x11vnc login
              will always *FAIL* for this case (even when the correct password
              is supplied).

              A  possible workaround for this on *BSD would be to start x11vnc
              as root with the "-users +nobody" option to  immediately  switch
              to user nobody where the su'ing will proceed normally.

              Another source of potential problems are PAM modules that prompt
              for extra info, e.g. password aging modules.  These logins  will
              fail as well even when the correct password is supplied.

              **IMPORTANT**: to prevent the Unix password being sent in *clear
              text* over the network, one of two schemes will be enforced:  1)
              the  -ssl  builtin  SSL  mode, or 2) require both -localhost and
              -stunnel be enabled.

              Method 1) ensures the traffic is encrypted  between  viewer  and
              server.   A  PEM file will be required, see the discussion under
              -ssl below (under some circumstances  a  temporary  one  can  be
              automatically generated).

              Method  2) requires the viewer connection to appear to come from
              the same machine x11vnc is running on (e.g. from a ssh  -L  port
              redirection).   And  that  the  -stunnel  SSL  mode  be used for
              encryption over the network. (see the  description  of  -stunnel
              below).

              Note:  as  a  convenience,  if you ssh(1) in and start x11vnc it
              will check if the environment variable SSH_CONNECTION is set and
              appears  reasonable.   If  it  does,  then  the -ssl or -stunnel
              requirement will be dropped since it is assumed  you  are  using
              ssh for the encrypted tunnelling.  -localhost is still enforced.
              Use -ssl or -stunnel to force SSL usage even  if  SSH_CONNECTION
              is set.

              To  override  the  above  restrictions  you  can set environment
              variables before starting x11vnc:

              Set UNIXPW_DISABLE_SSL=1 to disable  requiring  either  -ssl  or
              -stunnel (as under SSH_CONNECTION.)  Evidently you will be using
              a different method to encrypt the data between the vncviewer and
              x11vnc:  perhaps  ssh(1)  or  an  IPSEC VPN. -localhost is still
              enforced (however, see the next paragraph.)

              Set  UNIXPW_DISABLE_LOCALHOST=1  to   disable   the   -localhost
              requirement  in  -unixpw  modes.  One should never do this (i.e.
              allow the Unix passwords to be sniffed on  the  network.)   This
              also  disables the localhost requirement for reverse connections
              (see below.)

              Note that use of -localhost with  ssh(1)  (and  no  -unixpw)  is
              roughly  the  same  as requiring a Unix user login (since a Unix
              password or the user's public key authentication is used by sshd
              on the machine where x11vnc runs and only local connections from
              that machine are accepted).

              Regarding reverse connections (e.g. -R connect:host and -connect
              host),  when the -localhost constraint is in effect then reverse
              connections can only be used to  connect  to  the  same  machine
              x11vnc  is  running on (default port 5500).  Please use a ssh or
              stunnel port redirection to the viewer  machine  to  tunnel  the
              reverse connection over an encrypted channel.

              In  -inetd  mode  the Method 1) will be enforced (not Method 2).
              With -ssl in effect reverse connections are  disabled.   If  you
              override  this via env. var, be sure to also use encryption from
              the viewer to inetd.  Tip: you can also have  your  own  stunnel
              spawn  x11vnc in -inetd mode (thereby bypassing inetd).  See the
              FAQ for details.

              The user names in the comma separated [list] may  have  per-user
              options  after  a  ":",  e.g.  "fred:opts" where "opts" is a "+"
              separated list of  "viewonly",  "fullaccess",  "input=XXXX",  or
              "deny",  e.g.  "karl,wally:viewonly,boss:input=M".  For "input="
              it is the K,M,B,C described under -input.

              If an item in the list is "*" that means those options apply  to
              all  users.   It  ALSO  implies  all users are allowed to log in
              after supplying a valid password.  Use "deny" to explicitly deny
              some  users  if  you  use "*" to set a global option.  If [list]
              begins with the "!" character then "*" is ignored  for  checking
              if the user is allowed, but the option values associated with it
              do apply as normal.

              There are also some utilities for checking passwords  if  [list]
              starts  with the "%" character.  See the quick_pw() function for
              more details.  Description: "%-" or "%stdin" means read one line
              from  stdin.  "%stdin2"  means  read the username from the first
              stdin line and the password from the seconde stdin line.  "%env"
              means  it  is  in $UNIXPW env var.  A leading "%/" or "%." means
              read the first line from the filename that follows after  the  %
              character.  %  by  itself  means  prompt  for  the  username and
              password.  Otherwise: %user:pass   E.g. -unixpw  %fred:swordfish
              For the other cases user:pass is read from the indicated source.
              If the password is correct ´Y user' is printed and  the  program
              exit code is 0.  If the password is incorrect it prints 'N user'
              and the exit code is 1.  If there is some other error  the  exit
              code  is  2.   This  feature enables x11vnc to be a general unix
              user password checking tool; it could be used  from  scripts  or
              other  programs.   These  %  password  checks  also apply to the
              -unixpw_nis and -unixpw_cmd options.

              For the % password check, if the env. var. UNIXPW_CMD is set  to
              a  command  then it is run as the user (assuming the password is
              correct.)  The output of the command is not printed, the program
              or  script  must manage that by some other means.  The exit code
              of x11vnc will depend on the exit code of the  command  that  is
              run.

              Use  -nounixpw  to disable unixpw mode if it was enabled earlier
              in the cmd line (e.g. -svc mode)

       -unixpw_nis [list]

              As -unixpw above, however do not use su(1) but  rather  use  the
              traditional  getpwnam(3)  + crypt(3) method to verify passwords.
              All of the above -unixpw options and constraints apply.

              This mode requires that the  encrypted  passwords  be  readable.
              Encrypted  passwords  stored in /etc/shadow will be inaccessible
              unless x11vnc is run as root.

              This is called "NIS" mode simply because in most NIS setups user
              encrypted  passwords  are accessible (e.g. "ypcat passwd") by an
              ordinary user and so that user can authenticate ANY user.

              NIS is not required for this mode to work (only that getpwnam(3)
              return  the  encrypted password is required), but it is unlikely
              it will work (as an ordinary user) for most modern  environments
              unless  NIS is available.  On the other hand, when x11vnc is run
              as root it will be able to to access /etc/shadow even if NIS  is
              not  available  (note running as root is often done when running
              x11vnc from inetd and xdm/gdm/kdm).

              Looked at another way, if you do  not  want  to  use  the  su(1)
              method  provided  by  -unixpw  (i.e.  su_verify()),  you can run
              x11vnc as root and use -unixpw_nis.  Any users with passwords in
              /etc/shadow can then be authenticated.

              In  -unixpw_nis  mode,  under  no circumstances is x11vnc's user
              password  verifying  function  based  on  su  called  (i.e.  the
              function  su_verify()  that  runs /bin/su in a pseudoterminal to
              verify  passwords.)   However,  if  -unixpw_nis   is   used   in
              conjunction  with  the -find and -create -display WAIT:... modes
              then, if x11vnc is  running  as  root,  /bin/su  may  be  called
              externally to run the find or create commands.

       -unixpw_cmd cmd

              As  -unixpw  above,  however do not use su(1) but rather run the
              externally supplied command cmd.  The first line  of  its  stdin
              will  be the username and the second line the received password.
              If the command exits with status 0 (success) the VNC  user  will
              be accepted.  It will be rejected for any other return status.

              Dynamic  passwords  and  non-unix  passwords,  e.g. LDAP, can be
              implemented  this  way  by  providing  your  own  custom  helper
              program.   Note that the remote viewer is given 3 tries to enter
              the correct password, and so the program may be called in a  row
              that many (or more) times.

              If  a  list  of allowed users is needed to limit who can log in,
              use -unixpw [list] in addition to this option.

              In FINDDISPLAY and FINDCREATEDISPLAY modes the cmd will also  be
              run  with the RFB_UNIXPW_CMD_RUN env. var.  non-empty and set to
              the corresponding display find/create command.   The  first  two
              lines of input are the username and passwd as in the normal case
              described above.  To support FINDDISPLAY and  FINDCREATEDISPLAY,
              cmd  should  run  the  requested  command  as the user (and most
              likely refusing to run it if the password is not correct.)  Here
              is  an  example  script  (note it has a hardwired bogus password
              "abc"!)

              #!/bin/sh # Example x11vnc -unixpw_cmd script.  # Read the first
              two lines of stdin (user and passwd) read user read pass

              debug=0  if  [  $debug  = 1 ]; then echo "user: $user" 1>&2 echo
              "pass: $pass" 1>&2 env | egrep -i 'rfb|vnc' 1>&2 fi

              # Check if the password is valid.  # (A real example  would  use
              ldap  lookup, etc!)  if [ "X$pass" != "Xabc" ]; then exit 1    #
              incorrect password fi

              if [ "X$RFB_UNIXPW_CMD_RUN" = "X" ]; then  exit  0    #  correct
              password  else  #  Run  the requested command (finddisplay) if [
              $debug = 1 ]; then echo "run: $RFB_UNIXPW_CMD_RUN" 1>&2 fi  exec
              /bin/su - "$user" -c "$RFB_UNIXPW_CMD_RUN" fi exit 1

              In  -unixpw_cmd  mode,  under  no circumstances is x11vnc's user
              password  verifying  function  based  on  su  called  (i.e.  the
              function  su_verify()  that  runs /bin/su in a pseudoterminal to
              verify passwords.)  It is up to the supplied  unixpw_cmd  to  do
              user  switching  if  desired and if it has the permissions to do
              so.

              See also "-passwdfile custom:..." above for a non unix  username
              based custom password checking interface.

       -find

              Find  the user's display using FINDDISPLAY. This is an alias for
              "-display WAIT:cmd=FINDDISPLAY".

              Note: if a -display occurs later on the  command  line  it  will
              override the -find setting.

              For  this  and the next few options see -display WAIT:...  below
              for all of the details.

       -finddpy

              Run the FINDDISPLAY program, print out  the  found  display  (if
              any)     and     exit.     Output    is    like:    DISPLAY=:0.0
              DISPLAY=:0.0,XPID=12345  or  DISPLAY=:0.0,VT=7.   XPID  is   the
              process  ID  of  the  found  X  server.  VT is the Linux virtual
              terminal of the X server.

       -listdpy

              Have the FINDDISPLAY program list all of your displays (i.e. all
              the  X displays on the local machine that you have access rights
              to).  x11vnc then exits.

       -findauth [disp]

              Apply  the  -find/-finddpy  heuristics  to  try  to  guess   the
              XAUTHORITY  file for DISPLAY 'disp'.  If 'disp' is not supplied,
              then the value in the -display on the cmdline is  used;  failing
              that  $DISPLAY  is  used; and failing that ":0" is used.  x11vnc
              then exits.

              If nothing is printed out, that means no  XAUTHORITY  was  found
              for 'disp'; i.e. failure.  If "XAUTHORITY=" is printed out, that
              means  use  the  default  (i.e.  do  not  set  XAUTHORITY).   If
              "XAUTHORITY=/path/to/file" is printed out, then use that file.

              XDM/GDM/KDM:  if you are running x11vnc as root and want to find
              the XAUTHORITY before anyone has logged into an X  session  yet,
              use:  x11vnc  -env  FD_XDM=1 -findauth ...  (This will also find
              the XAUTHORITY if a user is already logged into the X  session.)
              When  running  as  root,  FD_XDM=1  will be tried if the initial
              -findauth fails.

       -create

              First try to find the user's display using FINDDISPLAY, if  that
              doesn't  succeed  create  an X session via the FINDCREATEDISPLAY
              method.      This     is     an     alias     for      "-display
              WAIT:cmd=FINDCREATEDISPLAY-Xvfb".

              Note:  if  a  -display  occurs later on the command line it will
              override the -create setting.

              SSH NOTE: for both -find and -create you can (should!)  add  the
              "-localhost" option to force SSH tunnel access.

       -xdummy

              As in -create, except Xdummy instead of Xvfb.

       -xvnc

              As in -create, except Xvnc instead of Xvfb.

       -xvnc_redirect

              As in -create, except Xvnc.redirect instead of Xvfb.

       -xdummy_xvfb

              Sets WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb

       -create_xsrv str

              Sets  WAIT:cmd=FINDCREATEDISPLAY-<str>   Can be on cmdline after
              anything that sets WAIT:.. and other things (e.g. -svc, -xdmsvc)
              to  adjust  the  X  server list.  Example: -svc ... -create_xsrv
              Xdummy,X

       -svc

              Terminal services mode based on SSL access.  Alias for  -display
              WAIT:cmd=FINDCREATEDISPLAY-Xvfb -unixpw -users unixpw= -ssl SAVE
              Also "-service".

              Note: if a -display, -unixpw, -users, or -ssl  occurs  later  on
              the command line it will override the -svc setting.

       -svc_xdummy

              As -svc except Xdummy instead of Xvfb.

       -svc_xvnc

              As -svc except Xvnc instead of Xvfb.

       -svc_xdummy_xvfb

              As -svc with Xdummy,Xvfb.

       -xdmsvc

              Display  manager Terminal services mode based on SSL.  Alias for
              -display  WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp  -unixpw  -users
              unixpw= -ssl SAVE  Also "-xdm_service".

              Note:  if  a  -display, -unixpw, -users, or -ssl occurs later on
              the command line it will override the -xdmsvc setting.

              To create a session a user will have to  first  log  in  to  the
              -unixpw  dialog and then log in again to the XDM/GDM/KDM prompt.
              Subsequent  re-connections  will  only   require   the   -unixpw
              password.   See  the discussion under -display WAIT:... for more
              details about XDM, etc configuration.

              Remember to enable XDMCP in the xdm-config, gdm.conf,  or  kdmrc
              configuration file.  See -display WAIT: for more info.

       -sshxdmsvc

              Display  manager Terminal services mode based on SSH.  Alias for
              -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp -localhost.

              The -localhost option constrains connections to come  in  via  a
              SSH  tunnel (which will require a login).  To create a session a
              user will also  have  to  log  into  the  XDM  GDM  KDM  prompt.
              Subsequent  re-connections will only only require the SSH login.
              See the discussion under  -display  WAIT:...  for  more  details
              about XDM, etc configuration.

              Remember  to  enable XDMCP in the xdm-config, gdm.conf, or kdmrc
              configuration file.  See -display WAIT: for more info.

       -unixpw_system_greeter

              Present a "Press 'Escape' for  System  Greeter"  option  to  the
              connecting   VNC   client   in   combined   -unixpw   and  xdmcp
              FINDCREATEDISPLAY modes (e.g. -xdmsvc).

              Normally in a -unixpw mode the VNC client must  supply  a  valid
              username   and   password   to   gain   access.    However,   if
              -unixpw_system_greeter is  supplied  AND  the  FINDCREATEDISPLAY
              command  matches  'xdmcp', then the user has the option to press
              Escape and then get a XDM/GDM/KDM login/greeter  panel  instead.
              They  will  then  supply a username and password directly to the
              greeter.

              Otherwise, in xdmcp FINDCREATEDISPLAY mode the user must  supply
              his  username  and  password TWICE.  First to the initial unixpw
              login dialog, and second to the subsequent XDM/GDM/KDM  greeter.
              Note  that if the user re-connects and supplies his username and
              password in the unixpw dialog the xdmcp greeter is  skipped  and
              he  is  connected  directly  to  his existing X session.  So the
              -unixpw_system_greeter option avoids the  extra  password  at  X
              session creation time.

              Example:   x11vnc -xdmsvc -unixpw_system_greeter See -unixpw and
              -display WAIT:... for more info.

              The special options after a colon at the  end  of  the  username
              (e.g.  user:solid)  described  under  -display  WAIT:  are  also
              applied in this mode if they are typed in before the  user  hits
              Escape.  The username is ignored but the colon options are not.

              The  default  message  is  2 lines in a small font, set the env.
              var. X11VNC_SYSTEM_GREETER1=true for  a  1  line  message  in  a
              larger font.

              If the user pressed Escape the FINDCREATEDISPLAY command will be
              run with the env. var. X11VNC_XDM_ONLY=1.

              Remember to enable XDMCP in the xdm-config, gdm.conf,  or  kdmrc
              configuration file.  See -display WAIT: for more info.

       -redirect port

              As   in  FINDCREATEDISPLAY-Xvnc.redirect  mode  except  redirect
              immediately (i.e. without X session finding or  creation)  to  a
              VNC  server  listening on port. You can also supply host:port to
              redirect to a different machine.

              If 0 <= port < 200 it is taken as a VNC display (5900  is  added
              to get the actual port), if port < 0 then -port is used.

              Probably  the  only  reason  to  use  the -redirect option is in
              conjunction with SSL support, e.g. -ssl SAVE.  This provides  an
              easy  way  to  add  SSL encryption to a VNC server that does not
              support SSL (e.g. Xvnc or vnc.so) In fact, the protocol does not
              even  need to be VNC, and so "-rfbport port1 -ssl SAVE -redirect
              host:port2" can act as a replacement for stunnel(1).

              This mode only allows one redirected connection.   The  -forever
              option  does  not  apply.   Use  -inetd  or -loop for persistent
              service.

       -display WAIT:...

              A special usage mode for the  normal  -display  option.   Useful
              with  -unixpw,  but  can  be  used  independently of it.  If the
              display string begins with WAIT: then x11vnc waits until  a  VNC
              client connects before opening the X display (or -rawfb device).

              This  could  be  useful  for  delaying  opening  the display for
              certain usage modes (say if x11vnc is started at boot  time  and
              no X server is running or users logged in yet).

              If  the string is, e.g. WAIT:0.0 or WAIT:1, i.e. "WAIT" in front
              of a normal X display, then that indicated display is used.

              One  can  also  insert   a   geometry   between   colons,   e.g.
              WAIT:1280x1024:... to set the size of the display the VNC client
              first attaches to since some VNC viewers will not  automatically
              adjust to a new framebuffer size.

              A more interesting case is like this:

              WAIT:cmd=/usr/local/bin/find_display

              in  which  case  the  command after "cmd=" is run to dynamically
              work out the DISPLAY and optionally the  XAUTHORITY  data.   The
              first   line   of  the  command  output  must  be  of  the  form
              DISPLAY=<xdisplay>.  On Linux if the virtual terminal  is  known
              append  ",VT=n" to this string and the chvt(1) program will also
              be run.  Any remaining output is taken as XAUTHORITY  data.   It
              can  be  either  of the form XAUTHORITY=<file> or raw xauthority
              data for the display. For example;

              xauth extract - $DISPLAY"

              NOTE: As specified in the previous  paragraph,  you  can  supply
              your  own WAIT:cmd=... program or script, BUT there are two very
              useful *BUILT-IN* ones:  FINDDISPLAY  (alias  -find  above)  and
              FINDCREATEDISPLAY  (alias -create above.)  Most people use these
              instead of  creating  their  own  script.   Read  the  following
              (especially the BUILT-IN modes sections) to see how to configure
              these two useful builtin -display WAIT: modes.

              In the case of  -unixpw  (and  -unixpw_nis  only  if  x11vnc  is
              running  as  root), then the cmd= command is run as the user who
              just authenticated via the login and password prompt.

              In the case of -unixpw_cmd, the commands will also be run as the
              logged-in  user,  as  long  as  the user-supplied helper program
              supports RFB_UNIXPW_CMD_RUN (see the -unixpw_cmd option.)

              Also in the case of -unixpw, the user logging  in  can  place  a
              colon  at  the  end  of  her  username and supply a few options:
              scale=, scale_cursor= (or sc=), solid (or so),  id=,  clear_mods
              (or  cm), clear_keys (or ck), clear_all (or ca), repeat, speeds=
              (or sp=), readtimeout= (or rd=), viewonly  (or  vo),  nodisplay=
              (or  nd=),  rotate= (or ro=), or noncache (or nc), all separated
              by commas if there is more than one.  After  the  user  logs  in
              successfully,  these  options will be applied to the VNC screen.
              For example,

              login: fred:scale=3/4,sc=1,repeat Password: ...

              login: runge:sp=modem,rd=120,solid

              for convenience m/n implies scale= e.g. fred:3/4   If  you  type
              and  enter  your  password  incorrectly,  to  retrieve your long
              "login:" line press the Up arrow once  (before  typing  anything
              else).

              Most   of   these  colon  options  only  apply  to  the  builtin
              FINDDISPLAY and FINDCREATEDISPLAY modes, but note that they  are
              passed to the extrenal command in the environment as well and so
              could be used.

              In the login panel, press F1 to get  a  list  of  the  available
              options that you can add after the username.

              Another option is "geom=WxH" or "geom=WxHxD" (or ge=). This only
              has an effect in FINDCREATEDISPLAY mode when a virtual X  server
              such  as  Xvfb  is  going  to be created.  It sets the width and
              height of the new display, and optionally  the  color  depth  as
              well.

              You  can  also  supply  "gnome",  "kde",  "twm",  "fvwm", "mwm",
              "dtwm", "wmaker", "xfce", "lxde",  "enlightenment",  "Xsession",
              or  "failsafe" (same as "xterm") to have the created display use
              that mode for the user session.

              Specify "tag=..." to set the unique FD_TAG desktop  session  tag
              described  below.   Note:  this  option  will  be ignored if the
              FD_TAG env. var. is already set or if the  viewer-side  supplied
              value  is  not completely composed of alphanumeric or '_' or '-'
              characters.

              User preferences file:  Instead  of  having  the  user  type  in
              geom=WxH,...  etc. every time he logs in to find or create his X
              session, if you set FD_USERPREFS  to  a  string  that  does  not
              contain  the  "/"  character,  then the user's home directory is
              prepended to that string and if the file exists its  first  line
              is  read  and  appended to any options he supplied at the login:
              prompt.  For example -env  FD_USERPREFS=.x11vnc_create  and  the
              user put "geom=1600x1200" in his ~/.x11vnc_create file.

              To  disable  the  option  setting  set  the environment variable
              X11VNC_NO_UNIXPW_OPTS=1 before  starting  x11vnc.   To  set  any
              other options, the user can use the gui (x11vnc -gui connect) or
              the remote control method (x11vnc -R  opt:val)  during  his  VNC
              session.

              So  we  see the combination of -display WAIT:cmd=... and -unixpw
              allows automatic pairing of an unix authenticated VNC user  with
              his  desktop.  This could be very useful on SunRays and also any
              system where multiple users share a  given  machine.   The  user
              does  not need to remember special ports or passwords set up for
              his desktop and VNC.

              A  nice  way  to  use  WAIT:cmd=...  is  out  of  inetd(8)   (it
              automatically  forks  a new x11vnc for each user).  You can have
              the x11vnc inetd spawned process run as, say,  root  or  nobody.
              When  run as root (for either inetd or display manager), you can
              also supply the option  "-users  unixpw="  to  have  the  x11vnc
              process  switch  to the user as well.  Note: there will be a 2nd
              SSL helper process that will not switch, but it is only encoding
              and decoding the encrypted stream at that point.

              BUILT-IN modes:

              -- Automatic Finding of User X Sessions --

              As  a  special case, WAIT:cmd=FINDDISPLAY will run a script that
              works on most Unixes to determine a user's DISPLAY variable  and
              xauthority data (see who(1) ).

              NOTE: The option "-find" is an alias for this mode.

              To  have  this  default  script  printed  to  stdout  (e.g.  for
              customization) run with WAIT:cmd=FINDDISPLAY-print To  have  the
              script run to print what display it would find use "-finddpy" or
              WAIT:cmd=FINDDISPLAY-run

              The standard script runs xdpyinfo(1) run on potential  displays.
              If  your X server(s) have a login greeter that exclusively grabs
              the Xserver, then xdpyinfo blocks forever and this mode will not
              work.  See www.karlrunge.com/x11vnc/faq.html#faq-display-manager
              for how to disable this for dtgreet on Solaris and possibly  for
              other greeters.

              In -find/cmd=FINDDISPLAY mode, if you set FD_XDM=1, e.g. 'x11vnc
              -env FD_XDM=1 -find ...' and x11vnc is  running  as  root  (e.g.
              inetd) then it will try to find the XAUTHORITY file of a running
              XDM/GDM/KDM login greeter (i.e. no user has  logged  into  an  X
              session yet.)

              As  another special case, WAIT:cmd=HTTPONCE will allow x11vnc to
              service one http request and then exit.  This is usually done in
              -inetd  mode  to  run  on,  say,  port  5800  and allow the Java
              vncviewer to be downloaded by client web browsers.  For example:

              5815 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc \  -inetd
              -q -http_ssl -prog /.../x11vnc \ -display WAIT:cmd=HTTPONCE

              Where /.../x11vnc is the full path to x11vnc.  It is used in the
              Apache SSL-portal example (see FAQ).

              In  this  mode  you  can  set  X11VNC_SKIP_DISPLAY  to  a  comma
              separated  list  of  displays  (e.g.  ":0,:1")  to ignore in the
              finding process.  The ":" is optional.  Ranges n-m e.g. 0-20 can
              also  be supplied. This string can also be set by the connecting
              user via "nd=" using "+" instead of ","  If "nd=all" or you  set
              X11VNC_SKIP_DISPLAY=all then all display finding fails as if you
              set X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (below.)

              On some systems lsof(1) can be very slow.   Set  the  env.  var.
              FIND_DISPLAY_NO_LSOF=1  to  skip  using  lsof to try to find the
              Linux   VT    the    X    server    is    running    on.     set
              FIND_DISPLAY_NO_VT_FIND=1 to avoid looking at all.

              -- Automatic Creation of User X Sessions --

              An interesting option is WAIT:cmd=FINDCREATEDISPLAY that is like
              FINDDISPLAY in that is uses the same method to find an  existing
              display.   However,  if  it  does  not  find  one it will try to
              *start* up an X server session for the user.  This is  the  only
              time x11vnc tries to actually start up an X server.

              NOTE: The option "-create" is an alias for this mode.

              It will start looking for an open display number at :20 Override
              via  X11VNC_CREATE_STARTING_DISPLAY_NUMBER=n  By  default  80  X
              displays   are   allowed   (i.e.  going  to  :99)  Override  via
              X11VNC_CREATE_MAX_DISPLAYS=n

              For its heuristics, the create display script sets  LC_ALL=C  so
              that  command  output  is  uniform.   By  default it will try to
              restore LC_ALL right before starting the user session.  However,
              if  you  don't  mind  it  keeping  LC_ALL=C  set  the env. var.:
              X11VNC_CREATE_LC_ALL_C_OK=1

              By default FINDCREATEDISPLAY will try Xvfb and then Xdummy:

              The  Xdummy  wrapper  is  part  of  the   x11vnc   source   code
              (x11vnc/misc/Xdummy)   It  should  be available in PATH and have
              run "Xdummy -install" once to create the shared library.  Xdummy
              only works on Linux.  As of 12/2009 it no longer needs to be run
              as root, and the default  is  to  not  run  as  root.   In  some
              circumstances  permissions  may  require  running it as root, in
              these cases specify FD_XDUMMY_RUN_AS_ROOT=1, this is the same as
              supplying -root to the Xdummy cmdline.

              Xvfb is available on most platforms and does not require root.

              An  advantage  of Xdummy over Xvfb is that Xdummy supports RANDR
              dynamic screen resizing.

              When x11vnc exits (i.e. user disconnects) the X  server  session
              stays  running  in the background.  The FINDDISPLAY will find it
              directly next time.  The user must exit the  X  session  in  the
              usual  way  for it to terminate (or kill the X server process if
              all else fails).

              To  troubleshoot  the  FINDCREATEDISPLAY  mechanism,   set   the
              following   env.   var.   to   an  output  log  file,  e.g  -env
              CREATE_DISPLAY_OUTPUT=/tmp/mydebug.txt

              So this is a somewhat odd mode for x11vnc in that it will  start
              up  and  poll  virtual  X  servers!  This can be used from, say,
              inetd(8) to provide a means  of  definitely  getting  a  desktop
              (either  real  or  virtual)  on  the  machine.   E.g.  a desktop
              service:

              5900 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc -inetd -q
              -http  -ssl  SAVE  -unixpw  -users unixpw=\ -passwd secret -prog
              /.../x11vnc \ -display WAIT:cmd=FINDCREATEDISPLAY

              Where /.../x11vnc is the full path to x11vnc.

              See the -svc/-service option alias above.

              If for some reason you do not want x11vnc to ever try to find an
              existing        display       set       the       env.       var
              X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (also -env ...)  This  is  the
              same  as  setting  X11VNC_SKIP_DISPLAY=all or supplying "nd=all"
              after "username:"

              Use WAIT:cmd=FINDCREATEDISPLAY-print to  print  out  the  script
              that is used for this.

              You   can  specify  the  preferred  X  server  order  via  e.g.,
              WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb,X  and/or leave out  ones
              you do not want.  The the case "X" means try to start up a real,
              hardware X server using xinit(1)  or  startx(1).   If  there  is
              already  an  X  server running the X case may only work on Linux
              (see startx(1) ).

              "Xvnc" will start up a VNC X server (real-  or  tight-vnc,  e.g.
              use  if Xvfb is not available).  "Xsrv" will start up the server
              program in the variable "FD_XSRV" if it is  non-empty.  You  can
              make  this  be  a wrapper script if you like (it must handle :N,
              -geometry, and -depth and other X server options).

              You   can   set   the   environment   variable    FD_GEOM    (or
              X11VNC_CREATE_GEOM)  to WxH or WxHxD to set the width and height
              and optionally the color depth of the created display.  You  can
              also   set  FD_SESS  to  be  the  session  (short  name  of  the
              windowmanager:  kde,  gnome,  twm,  failsafe,   etc.).   FD_OPTS
              contains extra options to pass to the X server. You can also set
              FD_PROG  to  be  the  full  path  to  the  session/windowmanager
              program.

              More  FD tricks:  FD_CUPS=port or FD_CUPS=host:port will set the
              cups  printing  environment.   Similarly  for   FD_ESD=port   or
              FD_ESD=host:port  for esddsp sound redirection.  Set FD_EXTRA to
              a command to be run a few seconds after the X server starts  up.
              Set  FD_TAG to be a unique name for the session, it is set as an
              X property, that makes FINDDISPLAY only find sessions with  that
              tag value.

              Set  FD_XDMCP_IF  to  the  network  interface  that  the display
              manager is running on; default is 'localhost' but you  may  need
              to  set  it  to '::1' on some IPv6 only systems or misconfigured
              display managers.

              If you want the FINDCREATEDISPLAY session to  contact  an  XDMCP
              login  manager  (xdm/gdm/kdm)  on  the  same  machine,  then use
              "Xvfb.xdmcp" instead of "Xvfb", etc.   The  user  will  have  to
              supply  his  username and password one more time (but he gets to
              select his desktop type so that can be  useful).   For  this  to
              work, you will need to enable localhost XDMCP (udp port 177) for
              the display manager.  This seems to be:

              for gdm in gdm.conf:   Enable=true in section [xdmcp] for kdm in
              kdmrc:       Enable=true  in  section  [Xdmcp]  for  xdm in xdm-
              config: DisplayManager.requestPort: 177

              See  the  shorthand  options   above   "-svc",   "-xdmsvc"   and
              "-sshxdmsvc"  that  specify  the  above  options for some useful
              cases.

              If you set the  env.  var  WAITBG=1  x11vnc  will  go  into  the
              background once listening in wait mode.

              Another  special  mode  is  FINDCREATEDISPLAY-Xvnc.redirect, (or
              FINDDISPLAY-Xvnc.redirect).  In this case it will start up  Xvnc
              as above if needed, but instead of polling it in its normal way,
              it simply does a socket redirection of the connected VNC  viewer
              to the Xvnc.

              So  in Xvnc.redirect x11vnc does no VNC but merely transfers the
              data back and  forth.   This  should  be  faster  then  x11vnc's
              polling  method,  but  not as fast as connecting directly to the
              Xvnc with the VNC Viewer.  The idea here is to take advantage of
              x11vnc's display finding/creating scheme, SSL, and perhaps a few
              others.  Most of x11vnc's options do not apply in this mode.

              Xvnc.redirect should also work for the vnc.so  X  server  module
              for  the  h/w  display however it will work only for finding the
              display and the user must already be logged into the X console.

       -vencrypt mode

              The VeNCrypt extension to  the  VNC  protocol  allows  encrypted
              SSL/TLS connections.  If the -ssl mode is enabled, then VeNCrypt
              is enabled as well BY DEFAULT (they both use a  SSL/TLS  tunnel,
              only the protocol handshake is a little different.)

              To  control  when  and  how  VeNCrypt  is used, specify the mode
              string.  If mode is "never", then VeNCrypt is not used.  If mode
              is  "support" (the default) then VeNCrypt is supported.  If mode
              is "only", then the similar and older ANONTLS  protocol  is  not
              simultaneously  supported.   x11vnc's  normal SSL mode (vncs://)
              will be supported under -ssl unless you set mode to "force".

              If mode is prefixed with "nodh:", then Diffie Hellman  anonymous
              key  exchange  is disabled.  If mode is prefixed with "nox509:",
              then X509 key exchange is disabled.

              To disable all Anonymous Diffie-Hellman access  (susceptible  to
              Man-In-The-Middle  attack)  you  will  need to supply "-vencrypt
              nodh:support -anontls never" or "-vencrypt nodh:only"

              If mode is prefixed  with  "newdh:",  then  new  Diffie  Hellman
              parameters  are  generated for each connection (this can be time
              consuming: 1-60 secs; see -dhparams  below  for  a  faster  way)
              rather than using the fixed values in the program.  Using fixed,
              publicly known values is not known to  be  a  security  problem.
              This setting applies to ANONTLS as well.

              Long example: -vencrypt newdh:nox509:support

              Also, if mode is prefixed with "plain:", then if -unixpw mode is
              active the VeNCrypt "*Plain" username+passwd method  is  enabled
              for  Unix  logins.   Otherwise  in -unixpw mode the normal login
              panel is provided.

              You *MUST* supply the -ssl option for  VeNCrypt  to  be  active.
              The -vencrypt option only fine-tunes its operation.

       -anontls mode

              The  ANONTLS  extension  to  the  VNC  protocol allows encrypted
              SSL/TLS connections.  If the -ssl mode is enabled, then  ANONTLS
              is  enabled  as well BY DEFAULT (they both use a SSL/TLS tunnel,
              only the protocol handshake is a little different.)

              ANONTLS is an older SSL/TLS mode introduced by vino.

              It is referred to as 'TLS' for its registered VNC  security-type
              name,  but we use the more descriptive ´ANONTLS' here because it
              provides only Anonymous  Diffie-Hellman  encrypted  connections,
              and hence no possibility for certificate authentication.

              To  control  when  and  how  ANONTLS  is  used, specify the mode
              string.  If mode is "never", then ANONTLS is not used.  If  mode
              is  "support"  (the default) then ANONTLS is supported.  If mode
              is  "only",  then  the  similar   VeNCrypt   protocol   is   not
              simultaneously  supported.   x11vnc's  normal SSL mode (vncs://)
              will be supported under -ssl unless you set mode to "force".

              If mode is prefixed  with  "newdh:",  then  new  Diffie  Hellman
              parameters  are  generated for each connection (this can be time
              consuming: 1-60 secs; see -dhparams  below  for  a  faster  way)
              rather than using the fixed values in the program.  Using fixed,
              publicly known values is not known to  be  a  security  problem.
              This  setting  applies to VeNCrypt as well.  See the description
              of "plain:" under -vencrypt.

              Long example: -anontls newdh:plain:support

              You *MUST* supply the -ssl option for ANONTLS to be active.  The
              -anontls option only fine-tunes its operation.

       -sslonly

              Same  as: "-vencrypt never -anontls never"  i.e. it disables the
              VeNCrypt and ANONTLS encryption methods and only allows standard
              SSL  tunneling.   You  must also supply the -ssl ... option (see
              below.)

       -dhparams file

              For some operations a set of Diffie  Hellman  parameters  (prime
              and generator) is needed.  If so, use the parameters in file. In
              particular, the VeNCrypt and  ANONTLS  anonymous  DH  mode  need
              them.   By default a fixed set is used. If you do not want to do
              that you can specify "newdh:"  to  the  -vencrypt  and  -anontls
              options to generate a new set each session.  If that is too slow
              for you, use -dhparams file to a set you  created  manually  via
              "openssl dhparam -out file 1024"

       -nossl

              Disable  the  -ssl  option  (see  below).  Since  -ssl is off by
              default -nossl would only be used on the  commandline  to  unset
              any *earlier* -ssl option (or -svc...)

       -ssl [pem]

              Use  the openssl library (www.openssl.org) to provide a built-in
              encrypted SSL/TLS tunnel between VNC viewers and  x11vnc.   This
              requires  libssl  support  to  be  compiled into x11vnc at build
              time.  If x11vnc is not built with libssl support it  will  exit
              immediately  when  -ssl  is prescribed.  See the -stunnel option
              below for an alternative.

              The VNC Viewer-side needs to support SSL/TLS as well.  See  this
              URL and also the discussion below for ideas on how to enable SSL
              support              for               the               viewer:
              http://www.karlrunge.com/x11vnc/faq.html#faq-ssl-tun nel-viewers
              .  x11vnc provides an SSL enabled  Java  viewer  applet  in  the
              classes/ssl  directory  (-http  or -httpdir options.)  The SSVNC
              viewer package supports SSL tunnels too.

              If  the  VNC  Viewer  supports  VeNCrypt  or   ANONTLS   (vino's
              encryption  mode)  they are also supported by the -ssl mode (see
              the -vencrypt and -anontls options for more info;  use  -sslonly
              to disable both of them.)

              Use  "-ssl  /path/to/mycert.pem"  to  specify an SSL certificate
              file in PEM format to use to identify and provide a key for this
              server.   See  openssl(1)  for  more  info  about  PEMs  and the
              -sslGenCert and "-ssl SAVE" options  below  for  how  to  create
              them.

              The  connecting  VNC  viewer  SSL  tunnel  can  (at  its option)
              authenticate this server if it has the public key  part  of  the
              certificate  (or  a  common certificate authority, CA, is a more
              sophisticated way to verify this server's  cert,  see  -sslGenCA
              below).   This  authentication  is  done  to prevent Man-In-The-
              Middle attacks.  Otherwise, if the  VNC  viewer  simply  accepts
              this server's key WITHOUT verification, the traffic is protected
              from passive sniffing on the network, but *NOT* from Man-In-The-
              Middle  attacks.  There are hacker tools like dsniff/webmitm and
              cain that implement SSL Man-In-The-Middle attacks.

              If [pem] is empty or  the  string  "SAVE"  then  the  openssl(1)
              command  must be available to generate the certificate the first
              time.  A self-signed certificate is generated (see -sslGenCA and
              -sslGenCert  for  use  of  a Certificate Authority.)  It will be
              saved to the file ~/.vnc/certs/server.pem.  On subsequent  calls
              if that file already exists it will be used directly.

              Use  "SAVE_NOPROMPT"  to  avoid  being  prompted  to protect the
              generated key with a passphrase.   However  in  -inetd  and  -bg
              modes  there  will  be  no  prompting for a passphrase in either
              case.

              If [pem] is "SAVE_PROMPT" the  server.pem  certificate  will  be
              created  based  on your answers to its prompts for all info such
              as OrganizationalName, CommonName, etc.

              Use "SAVE-<string>" and "SAVE_PROMPT-<string>" to refer  to  the
              file   ~/.vnc/certs/server-<string>.pem   instead  (it  will  be
              generated if it does not already  exist).   E.g.  "SAVE-charlie"
              will store to the file ~/.vnc/certs/server-charlie.pem

              Examples:  x11vnc  -ssl  SAVE -display :0 ...  x11vnc -ssl SAVE-
              someother -display :0 ...

              If [pem] is "TMP" and the openssl(1) utility command  exists  in
              PATH,   then   a  temporary,  self-signed  certificate  will  be
              generated for this session.  If openssl(1)  cannot  be  used  to
              generate  a temporary certificate x11vnc exits immediately.  The
              temporary cert will be discarded when x11vnc exits.

              If successful  in  using  openssl(1)  to  generate  a  temporary
              certificate  in  "SAVE" or "TMP" creation modes, the public part
              of it will be displayed to stderr (e.g. one could copy it to the
              client-side  to  provide  authentication  of  the  server to VNC
              viewers.)

              NOTE: In "TMP" mode, unless you safely copy the public  part  of
              the  temporary  Cert to the viewer for authenticate *every time*
              (unlikely...), then only passive sniffing attacks are  prevented
              and  you  are  still open to Man-In-The-Middle attacks.  This is
              why the default "SAVE" mode is preferred (and more sophisticated
              CA  mode  too).   Only  with  saved  keys  AND  the  VNC  viewer
              authenticating them (via the public  certificate),  are  Man-In-
              The-Middle attacks prevented.

              If  [pem]  is  "ANON"  then  the  Diffie-Hellman  anonymous  key
              exchange method is used.   In  this  mode  there  are  *no*  SSL
              certificates  and  so  it is not possible to authenticate either
              the VNC  server  or  VNC  client.   Thus  only  passive  network
              sniffing  attacks  are avoided: the "ANON" method is susceptible
              to  Man-In-The-Middle  attacks.   "ANON"  is  not   recommended;
              instead use a SSL PEM you created or the default "SAVE" method.

              See  -ssldir  below  to  use  a  directory  besides  the default
              ~/.vnc/certs

              If your x11vnc binary was  not  compiled  with  OpenSSL  library
              support, use of the -ssl option will induce an immediate failure
              and exit.  For such binaries, consider using the -stunnel option
              for SSL encrypted connections.

              Misc  Info:  In temporary cert creation mode "TMP", set the env.
              var. X11VNC_SHOW_TMP_PEM=1 to have x11vnc print out  the  entire
              certificate,  including  the PRIVATE KEY part, to stderr.  There
              are better ways to get/save this info.   See  "SAVE"  above  and
              "-sslGenCert" below.

       -ssltimeout n

              Set  SSL read timeout to n seconds.  In some situations (i.e. an
              iconified viewer in Windows) the viewer stops  talking  and  the
              connection  is  dropped after the default timeout (25s for about
              the first minute, 43200s later).  Set to zero to  poll  forever.
              Set to a negative value to use the builtin setting.

              Note  that  this  value does NOT apply to the *initial* ssl init
              connection.  The default timeout for that is  20sec.   Use  -env
              SSL_INIT_TIMEOUT=n to modify it.

       -sslnofail

              Exit  at the first SSL connection failure. Useful when scripting
              SSL connections (e.g. x11vnc is started via ssh) and you do  not
              want x11vnc waiting around for more connections, tying up ports,
              etc.

       -ssldir dir

              Use dir as an  alternate  ssl  certificate  and  key  management
              toplevel directory.  The default is ~/.vnc/certs

              This  directory  is  used to store server and other certificates
              and keys and also other materials.  E.g. in the  simplest  case,
              "-ssl SAVE" will store the x11vnc server cert in dir/server.pem

              Use  of  alternate  directories via -ssldir allows you to manage
              multiple VNC Certificate Authority (CA) keys.  Another use is if
              ~/.vnc/cert  is on an NFS share you might want your certificates
              and keys to be on a local filesystem to prevent network snooping
              (for example -ssldir /var/lib/x11vnc-certs).

              -ssldir affects nearly all of the other -ssl* options, e.g. -ssl
              SAVE, -sslGenCert, etc..

       -sslverify path

              For either of the -ssl or -stunnel modes, use  path  to  provide
              certificates  to  authenticate incoming VNC *Client* connections
              (normally only the server is authenticated in SSL.)  This can be
              used  as a method to replace standard password authentication of
              clients.

              If  path  is  a  directory  it  contains  the  client  (or   CA)
              certificates  in separate files.  If path is a file, it contains
              one or more  certificates.  See  special  tokens  below.   These
              correspond  to  the  "CApath  = dir" and "CAfile = file" stunnel
              options.  See the stunnel(8) manpage for details.

              Examples: x11vnc -ssl -sslverify ~/my.crt x11vnc -ssl -sslverify
              ~/my_pem_dir/

              Note  that  if path is a directory, it must contain the certs in
              separate files named like <HASH>.0, where the value of <HASH> is
              found  by  running  the  command  "openssl x509 -hash -noout -in
              file.crt".  Evidently  one  uses  <HASH>.1   if   there   is   a
              collision...

              The   the   key-management  utility  "-sslCertInfo  HASHON"  and
              "-sslCertInfo HASHOFF" will create/delete these hashes  for  you
              automatically  (via  symlink)  in  the  HASH subdirs it manages.
              Then you can point -sslverify to the HASH subdir.

              Special tokens: in -ssl mode,  if  path  is  not  a  file  or  a
              directory,  it is taken as a comma separated list of tokens that
              are interpreted as follows:

              If a token is "CA" that means load the CA/cacert.pem  file  from
              the  ssl  directory.  If a token is "clients" then all the files
              clients/*.crt in the ssl directory are  loaded.   Otherwise  the
              file  clients/token.crt is attempted to be loaded.  As a kludge,
              use a token like ../server-foo to load a server cert if you find
              that necessary.

              Use  -ssldir  to use a directory different from the ~/.vnc/certs
              default.

              Note that if the "CA" cert is loaded you do not need to load any
              of the certs that have been signed by it.  You will need to load
              any additional self-signed certs however.

              Examples: x11vnc  -ssl  -sslverify  CA  x11vnc  -ssl  -sslverify
              self:fred,self:jim x11vnc -ssl -sslverify CA,clients

              Usually   "-sslverify  CA"  is  the  most  effective.   See  the
              -sslGenCA and -sslGenCert options below for how to  set  up  and
              manage the CA framework.

              NOTE:   the   following   utilities,   -sslGenCA,   -sslGenCert,
              -sslEncKey,  -sslCertInfo,  and   -sslCRL   are   provided   for
              completeness, but for casual usage they are overkill.

              They  provide  VNC  Certificate  Authority (CA) key creation and
              server / client key generation and signing.  So they  provide  a
              basic  Public  Key management framework for VNC-ing with x11vnc.
              (note that they require openssl(1) be installed on the system)

              However, the simplest  usage  mode,  "-ssl  TMP"  (where  x11vnc
              automatically  generates its own, self-signed, temporary key and
              the VNC viewers always accept it, e.g. accepting  via  a  dialog
              box)  is probably safe enough for most scenarios.  CA management
              is not needed.

              To protect against Man-In-The-Middle attacks the "TMP" mode  can
              be  improved  by  using  "-ssl  SAVE"  (same as "-ssl", i.e. the
              default)  to  have  x11vnc  create  a  longer  term  self-signed
              certificate, and then (safely) copy the corresponding public key
              cert to the desired client machines  (care  must  be  taken  the
              private  key  part  is  not  stolen;  you will be prompted for a
              passphrase).

              So keep in mind no CA key creation or management (-sslGenCA  and
              -sslGenCert)  is needed for either of the above two common usage
              modes.

              One might want to use -sslGenCA and -sslGenCert  if  you  had  a
              large  number  of  VNC client and server workstations.  That way
              the administrator could generate a single CA key with  -sslGenCA
              and distribute its certificate part to all of the workstations.

              Next, he could create signed VNC server keys (-sslGenCert server
              ...) for each workstation or user that then x11vnc would use  to
              authenticate itself to any VNC client that has the CA cert.

              Optionally,  the  admin  could  also  make it so the VNC clients
              themselves are authenticated to x11vnc (-sslGenCert client  ...)
              For  this  -sslverify  would  be  pointed to the CA cert (and/or
              self-signed certs).

              x11vnc will be able to use all of these cert and key files.   On
              the  VNC  client  side, they will need to be "imported" somehow.
              Web browsers have "Manage Certificates" actions as does the Java
              applet  plugin  Control Panel.  stunnel can also use these files
              (see the ss_vncviewer example script in the FAQ and SSVNC.)

       -sslCRL path

              Set the  Certificate  Revocation  Lists  (CRL)  to  path.   This
              setting applies for both -ssl and -stunnel modes.

              If  path  is  a  file, the file contains one or more CRLs in PEM
              format.  If path is a directory, it contains hash named files of
              CRLs   in  the  usual  OpenSSL  manner.   See  the  OpenSSL  and
              stunnel(8) documentation for more info.

              This option only applies if -sslverify  has  been  supplied:  it
              checks for revocation along the certificate chain used to verify
              the VNC client.   The  -sslCRL  setting  will  be  ignored  when
              -sslverify is not specified.

              Note  that  if  a  CRL's  expiration  date  has  passed, all SSL
              connections will fail regardless of if they are related  to  the
              subject of the CRL or not.

              Only  rarely  will  one's x11vnc -ssl infrastructure be so large
              that this option would be useful (since normally maintaining the
              contents  of the -sslverify file or directory should be enough.)
              However, when using x11vnc with  a  Certificate  Authority  (see
              -sslGenCA)  to  authenticate  Clients  via  SSL/TLS, the -sslCRL
              option can be useful to revoke users' certs  whose  private  SSL
              keys  were  lost  or  stolen  (e.g.  laptop.)  This way a new CA
              cert+key does not need to be created and new signed client  keys
              generated and distributed to all users.

              To  create  a  CRL  file  with revoked certificates the commands
              'openssl ca -revoke  ...'  and  'openssl  ca  -gencrl  ...'  are
              useful.  (Run them in ~/.vnc/certs)

       -sslGenCA [dir]

              Generate   your   own   Certificate   Authority   private   key,
              certificate, and other files in directory  [dir].   x11vnc  then
              exits.

              If  [dir]  is  not  supplied,  a  -ssldir  setting  is  used, or
              otherwise ~/.vnc/certs is used.

              This command also creates directories where  server  and  client
              certs  and  keys will be stored.  The openssl(1) program must be
              installed on the system and available in PATH.

              After the CA  files  and  directories  are  created  the  x11vnc
              command exits; the VNC server is not run.

              You  will  be  prompted  for  information  to  put  into  the CA
              certificate.  The info does not have to be accurate just as long
              as  clients  accept the cert for VNC connections.  You will also
              need to supply a passphrase of at least 4 characters for the  CA
              private key.

              Once   you   have  generated  the  CA  you  can  distribute  its
              certificate part,  [dir]/CA/cacert.pem,  to  other  workstations
              where  VNC  viewers will be run.  One will need to "import" this
              certificate in the applications, e.g. Web browser,  Java  applet
              plugin,  stunnel, etc.  Next, you can create and sign keys using
              the CA with the -sslGenCert option below.

              Examples: x11vnc -sslGenCA x11vnc  -sslGenCA   ~/myCAdir  x11vnc
              -ssldir ~/myCAdir -sslGenCA

              (the last two lines are equivalent)

       -sslGenCert type name

              Generate a VNC server or client certificate and private key pair
              signed  by  the  CA  created  previously  with  -sslGenCA.   The
              openssl(1) program must be installed on the system and available
              in PATH.

              After the Certificate is generated x11vnc exits; the VNC  server
              is not run.

              The  type  of  key  to  be  generated is the string type.  It is
              either "server" (i.e. for use by x11vnc) or "client" (for a  VNC
              viewer).   Note  that  typically  only "server" is used: the VNC
              clients authenticate themselves by a non-public-key method (e.g.
              VNC or unix password).  type is required.

              An  arbitrary default name you want to associate with the key is
              supplied by the name string.  You can change it at  the  various
              prompts when creating the key.  name is optional.

              If  name  is  left blank for clients keys then "nobody" is used.
              If left blank for server keys,  then  the  primary  server  key:
              "server.pem"  is  created  (this  is the saved one referenced by
              "-ssl SAVE" when the server is started)

              If name begins  with  the  string  "self:"  then  a  self-signed
              certificate is created instead of one signed by your CA key.

              If name begins with the string "req:" then only a key (.key) and
              a certificate signing *request* (.req) are generated.   You  can
              then  send  the .req file to an external CA (even a professional
              one, e.g. Thawte) and then combine the  .key  and  the  received
              cert into the .pem file with the same basename.

              The  distinction  between  "server"  and  "client" is simply the
              choice of output filenames and sub-directory.  This makes it  so
              the -ssl SAVE-name option can easily pick up the x11vnc PEM file
              this option generates.  And similarly  makes  it  easy  for  the
              -sslverify option to pick up your client certs.

              There  is  nothing  special  about  the  filename  or  directory
              location of either the "server" and  "client"  certs.   You  can
              rename the files or move them to wherever you like.

              Precede  this option with -ssldir [dir] to use a directory other
              than the default ~/.vnc/certs You will need to run -sslGenCA  on
              that directory first before doing any -sslGenCert key creation.

              Note   you   cannot  recreate  a  cert  with  exactly  the  same
              distiguished name (DN) as an existing one.  To do so,  you  will
              need to edit the [dir]/CA/index.txt file to delete the line.

              Similar  to  -sslGenCA,  you  will  be  prompted to fill in some
              information that will be recorded in the certificate when it  is
              created.

              Tip:  if you know the fully-qualified hostname other people will
              be connecting to, you can use that as  the  CommonName  "CN"  to
              avoid  some  applications  (e.g.  web  browsers and java plugin)
              complaining that it does not match the hostname.

              You will also need to supply the CA private  key  passphrase  to
              unlock the private key created from -sslGenCA.  This private key
              is used to sign the server or client certificate.

              The "server" certs can be used by x11vnc directly by pointing to
              them  via  the  -ssl  [pem]  option.   The  default file will be
              ~/.vnc/certs/server.pem.  This  one  would  be  used  by  simply
              typing  -ssl  SAVE.   The pem file contains both the certificate
              and the private key.  server.crt file contains the cert only.

              The "client" cert + private key file will need to be copied  and
              imported  into  the  VNC  viewer side applications (Web browser,
              Java plugin, stunnel, etc.)  Once that is done  you  can  delete
              the  "client"  private key file on this machine since it is only
              needed    on    the    VNC    viewer    side.      The,     e.g.
              ~/.vnc/certs/clients/<name>.pem   contains  both  the  cert  and
              private key.  The <name>.crt contains the certificate only.

              NOTE: It is very important to know one should generate new  keys
              with  a  passphrase.   Otherwise if an untrusted user steals the
              key file he could use it to masquerade as the x11vnc server  (or
              VNC viewer client).  You will be prompted whether to encrypt the
              key with a passphrase or not.  It is recommended  that  you  do.
              One  inconvenience  to  a passphrase is that it must be typed in
              EVERY time x11vnc or the client app is started up.

              Examples:

              x11vnc -sslGenCert server x11vnc -ssl SAVE -display :0 ...

              and then on viewer using ss_vncviewer stunnel wrapper  (see  the
              FAQ): ss_vncviewer -verify ./cacert.crt hostname:0

              (this  assumes  the  cacert.crt  cert  from -sslGenCA was safely
              copied to the VNC viewer machine where ss_vncviewer is run)

              Example using a name:

              x11vnc  -sslGenCert  server  charlie  x11vnc  -ssl  SAVE-charlie
              -display :0 ...

              Example for a client certificate (rarely used):

              x11vnc         -sslGenCert        client        roger        scp
              ~/.vnc/certs/clients/roger.pem          somehost:.            rm
              ~/.vnc/certs/clients/roger.pem

              x11vnc    is   then   started   with   the   option   -sslverify
              ~/.vnc/certs/clients/roger.crt (or simply -sslverify roger), and
              on the viewer user on somehost could do for example:

              ss_vncviewer -mycert ./roger.pem hostname:0

              If  you  set  the  env.  var REQ_ARGS='...' it will be passed to
              openssl req(1).  A common use would be REQ_ARGS='-days 1095'  to
              bump up the expiration date (3 years in this case).

       -sslEncKey pem

              Utility  to  encrypt  an existing PEM file with a passphrase you
              supply when prompted.  For that key to be used (e.g. by  x11vnc)
              the passphrase must be supplied each time.

              The  "SAVE"  notation  described  under  -ssl  applies  as well.
              (precede this option with -ssldir [dir]  to  refer  a  directory
              besides the default ~/.vnc/certs)

              The  openssl(1)  program  must  be  installed  on the system and
              available in PATH.  After the Key file is encrypted  the  x11vnc
              command exits; the VNC server is not run.

              Examples:  x11vnc  -sslEncKey /path/to/foo.pem x11vnc -sslEncKey
              SAVE x11vnc -sslEncKey SAVE-charlie

       -sslCertInfo pem

              Prints out information about an existing PEM file.  In  addition
              the  public certificate is also printed.  The openssl(1) program
              must be in PATH. Basically the command "openssl x509  -text"  is
              run on the pem.

              After  the  info  is  printed  the x11vnc command exits; the VNC
              server is not run.

              The "SAVE" notation described under -ssl applies as well.

              Using  "LIST" will give a list of all certs  being  managed  (in
              the  ~/.vnc/certs  dir,  use  -ssldir  to refer to another dir).
              "ALL" will print out the info for every managed key (this can be
              very  long).  Giving a client or server cert shortname will also
              try a lookup (e.g. -sslCertInfo charlie).  Use "LISTL"  or  "LL"
              for a long (ls -l style) listing.

              Using  "HASHON"  will  create  subdirs [dir]/HASH and [dir]/HASH
              with OpenSSL hash filenames (e.g. 0d5fbbf1.0) symlinks  pointing
              up  to  the corresponding *.crt file.  ([dir] is ~/.vnc/certs or
              one given by -ssldir.)  This is a useful way for  other  OpenSSL
              applications  (e.g.  stunnel) to access all of the certs without
              having to concatenate them.  x11vnc will not use them unless you
              specifically  reference  them.   "HASHOFF"  removes  these  HASH
              subdirs.

              The LIST, LISTL, LL, ALL, HASHON,  HASHOFF  words  can  also  be
              lowercase, e.g. "list".

       -sslDelCert pem

              Prompts  you  to delete all .crt .pem .key .req files associated
              with [pem].   x11vnc  then  exits.  "SAVE"  and  lookups  as  in
              -sslCertInfo apply as well.

       -sslScripts

              Prints out both the 'genCA' and 'genCert' x11vnc openssl wrapper
              scripts for you  to  examine,  modify,  etc.   The  scripts  are
              printed to stdout and then the x11vnc program exits.

       -stunnel [pem]

              Use  the  stunnel(8)  (stunnel.mirt.net) to provide an encrypted
              SSL tunnel between viewers and x11vnc.

              This  external  tunnel  method  was  implemented  prior  to  the
              integrated -ssl encryption described above.  It still works well
              and  avoids  the  requirement  of  linking  with   the   OpenSSL
              libraries.   This  mode  requires stunnel to be installed on the
              system and available via PATH (n.b. stunnel is  often  installed
              in  sbin  directories).   Version 4.x of stunnel is assumed (but
              see -stunnel3 below.)

              [pem]  is  optional,  use  "-stunnel  /path/to/stunnel.pem"   to
              specify a PEM certificate file to pass to stunnel.  See the -ssl
              option for more info on certificate files.

              Whether or not your stunnel has its own certificate  depends  on
              your  stunnel  configuration;  stunnel  often  generates  one at
              install time.  See your stunnel documentation for  details.   In
              any  event,  if you want to use this certificate you must supply
              the full path to it as  [pem].   Note:  the  file  may  only  be
              readable by root.

              [pem]  may  also  be  the  special  strings  "TMP",  "SAVE", and
              "SAVE..." as described in the -ssl  option.   If  [pem]  is  not
              supplied, "SAVE" is assumed.

              Note  that  the  VeNCrypt,  ANONTLS,  and  "ANON"  modes are not
              supported in -stunnel mode.

              stunnel is started up as a child process of x11vnc and  any  SSL
              connections  stunnel  receives  are decrypted and sent to x11vnc
              over a local socket.  The strings "The SSL VNC desktop  is  ..."
              and "SSLPORT=..."  are printed out at startup to indicate this.

              The  -localhost  option  is  enforced by default to avoid people
              routing    around     the     SSL     channel.      Use     -env
              STUNNEL_DISABLE_LOCALHOST=1    to    disable    this    security
              requirement.

              Set -env STUNNEL_DEBUG=1 for more debugging printout.

              Set -env STUNNEL_PROG=xxx to the full path  of  stunnel  program
              you want to be used (e.g. /usr/bin/stunnel4).

              Set  -env  STUNNEL_LISTEN=xxx  to  the  address  of  the network
              interface to  listen  on  (the  default  is  to  listen  on  all
              interfaces), e.g. STUNNEL_LISTEN=192.168.1.100.

              A simple way to add IPv6 support is STUNNEL_LISTEN=::

              Your  VNC  viewer  will also need to be able to connect via SSL.
              Unfortunately not too many do this.  See the  information  about
              SSL  viewers  under the -ssl option.  The x11vnc project's SSVNC
              is an option.

              Also, in the x11vnc distribution, patched TightVNC and  UltraVNC
              Java  applet jar files are provided in the classes/ssl directory
              that do SSL connections.  Enable serving them  with  the  -http,
              -http_ssl,  or  -httpdir  (see  the option descriptions for more
              info.)

              Note that for the Java viewer applet usage the  "?PORT=xxxx"  in
              the  various URLs printed at startup will need to be supplied to
              the web browser to connect properly.

              Currently the automatic "single port" HTTPS mode of -ssl is  not
              fully  supported  in -stunnel mode.  However, it can be emulated
              via:

              % x11vnc -stunnel -http_ssl -http_oneport ...

              In general, it is also not too difficult to set up an stunnel or
              other  SSL  tunnel on the viewer side.  A simple example on Unix
              using stunnel 3.x is:

              % stunnel -c -d localhost:5901 -r  remotehost:5900  %  vncviewer
              localhost:1

              For  Windows,  stunnel  has  been  ported  to  it  and there are
              probably other such tools available.  See the FAQ and SSVNC  for
              more examples.

       -stunnel3 [pem]

              Use  version  3.x stunnel command line syntax instead of version
              4.x.  The -http/-httpdir Java applet serving  is  currently  not
              available in this mode.

       -enc cipher:keyfile

              Use  symmetric  encryption  with  cipher "cipher" and secret key
              data in "keyfile".  If keyfile is pw=<string> then  "string"  is
              used as the key data.

              NOTE:  It  is  recommended  that you use SSL via the -ssl option
              instead of this option because SSL is well understood and  takes
              great  care  to  establish  unique  session  keys  and  is  more
              compatible with other software.  Use this option if you  do  not
              want to deal with SSL certificates for authentication and do not
              want to use SSH but want some encryption for your  VNC  session.
              Or if you must interface with a symmetric key tunnel that you do
              not have control over.

              Note that this mode will NOT work with the UltraVNC DSM  plugins
              because  they  alter  the RFB protocol in addition to tunnelling
              with  the   symmetric   cipher   (an   unfortunate   choice   of
              implementation...)

              cipher  can  be one of:  arc4, aesv2, aes-cfb, blowfish, aes256,
              or 3des.  See the OpenSSL  documentation  for  more  info.   The
              keysize  is  128  bits  (except for aes256).  Here is one way to
              make a keyfile with that many bits:

              dd if=/dev/random of=./my.key bs=16 count=1

              you will need to securely share this key with the other side  of
              the VNC connection (See SSVNC for examples).

              Example:       -enc     blowfish:./my.key     Example:      -enc
              blowfish:pw=swordfish

              By default 16 bytes of random  salt  followed  by  16  bytes  of
              random  initialization  vector are sent at the very beginning of
              the stream.  The other side must read these and initialize their
              cipher  with  them.   These  values  make the session key unique
              (without them the security is minimal).   Similarly,  the  other
              side  must  send  us  its  random  salt  and  IV with those same
              lengths.

              The salt and key data are combined to create a session key using
              an md5 hash as described in EVP_BytesToKey(3).

              The  exact  call  is:  EVP_BytesToKey(Cipher,  EVP_md5(),  salt,
              keydata, len, 1, keystr, NULL);  where salt is the  random  data
              as  described  above, and keydata is the shared secret key data.
              keystr is the resulting session key.  The cipher is then  seeded
              with  keystr  and  uses  the random initialization vector as its
              first block.

              To modify the amount of random salt  and  initialization  vector
              use   cipher@n,m   where   n  is  the  salt  length  and  m  the
              initialization vector length.  E.g.

              -enc aes-cfb@8,16:./my.key

              It is not a good idea to set either one to  zero,  although  you
              may  be  forced  to if the other side of the tunnel is not under
              your control.

              To skip the salt and EVP_BytesToKey MD5 entirely (no hashing  is
              done:  the keydata is directly inserted into the cipher) specify
              "-1" for the salt, e.g.

              -enc blowfish@-1,16:./my.key

              The message digest can also be changed to something besides  the
              default  MD5.   Use  cipher@md+n,m where "md" can be one of sha,
              sha1, md5, or ripe.  For example:

              -enc arc4@sha+8,16:./my.key

              The SSVNC vnc viewer project  supplies  a  symmetric  encryption
              tool  named "ultravnc_dsm_helper" that can be used on the viewer
              side.  For example:

              ssvncviewer exec='ultravnc_dsm_helper arc4 my.key 0 h:p'

              (or replace 'ssvncviewer' with 'ssvnc -viewer') where h:p is the
              hostname and port of the x11vnc server.  ultravnc_dsm_helper may
              also be used standalone to provide a symmetric encryption tunnel
              for  any  viewer  or  server (VNC or otherwise.) The cipher (1st
              arg) is basically the same syntax as we use above.

              Also see the 'Non-Ultra DSM' SSVNC option for the ´UltraVNC  DSM
              Encryption Plugin' advanced option.

              For both ways of using the viewer, you can specify the salt,ivec
              sizes (in GUI or, e.g. arc4@8,16).

       -https [port]

              Use a special, separate HTTPS  port  (-ssl  and  -stunnel  modes
              only)  for  HTTPS  Java viewer applet downloading. I.e. not 5900
              and not 5800 (the defaults.)

              BACKGROUND: In -ssl mode, it turns out you can  use  the  single
              VNC  port (e.g. 5900) for both VNC and HTTPS connections. (HTTPS
              is used to retrieve a SSL-aware  VncViewer.jar  applet  that  is
              provided  with  x11vnc).   Since both use SSL the implementation
              was extended to detect if HTTP  traffic  (i.e.  GET)  is  taking
              place and handle it accordingly.  The URL would be, e.g.:

              https://mymachine.org:5900/

              This  is  convenient  for  firewalls, etc, because only one port
              needs to be allowed in.  However,  this  heuristic  adds  a  few
              seconds   delay   to  each  connection  and  can  be  unreliable
              (especially  if  the  user  takes  much  time  to   ponder   the
              Certificate  dialogs  in  his  browser,  Java  VM, or VNC Viewer
              applet.  That's right 3 separate  "Are  you  sure  you  want  to
              connect?" dialogs!)

              END OF BACKGROUND.

              USAGE:  So  use  the  -https  option to provide a separate, more
              reliable HTTPS port that x11vnc will listen on.   If  [port]  is
              not  provided (or is 0), one is autoselected.  The URL to use is
              printed out at startup.

              The SSL Java applet directory  is  specified  via  the  -httpdir
              option.  If not supplied, -https will try to guess the directory
              as though the -http option was supplied.

       -httpsredir [port]

              In -ssl mode with the Java applet retrieved via HTTPS, when  the
              HTML   file   containing   applet   parameters  ('index.vnc'  or
              'proxy.vnc') is sent do NOT set the applet PORT parameter to the
              actual  VNC port but set it to "port" instead.  If "port" is not
              supplied, then the port number is guessed from  the  Host:  HTTP
              header.

              This  is  useful  when an incoming TCP connection redirection is
              performed by a  router/gateway/firewall  from  one  port  to  an
              internal  machine where x11vnc is listening on a different port.
              The Java applet needs to connect to  the  firewall/router  port,
              not  the  VNC port on the internal workstation. For example, one
              could redir from mygateway.com:443 to workstation:5900.

              This   spares   the   user    from    having    to    type    in
              https://mygateway.com/?PORT=443  into  their  web  browser. Note
              that port 443 is the default https port;  other  ports  must  be
              explicitly           indicated,           for           example:
              https://mygateway.com:8000/?PORT=8000.   To  avoid   having   to
              include   the   PORT=   in   the   browser  URL,  simply  supply
              "-httpsredir" to x11vnc.

              This option does not work in -stunnel mode.

              More tricks: set the env  var  X11VNC_EXTRA_HTTPS_PARAMS  to  be
              extra  URL  parameters  to  use.   This  way  you do not need to
              specify extra PARAMS in the index.vnc file.   E.g.  x11vnc  -env
              X11VNC_EXTRA_HTTPS_PARAMS='?GET=1' ...

              If  you  do  not  want  to  expose  the non-SSL HTTP port to the
              network (i.e. you just want  the  single  VNC/HTTPS  port,  e.g.
              5900,  open  for  connections)  then  specify  the  option  -env
              X11VNC_HTTP_LISTEN_LOCALHOST=1  This way the connection  to  the
              LibVNCServer  httpd  server  will only be available on localhost
              (note that in -ssl mode, HTTPS requests are redirected from  SSL
              to the non-SSL LibVNCServer HTTP server.)

       -http_oneport

              For  UN-encrypted  connections  mode (i.e. no -ssl, -stunnel, or
              -enc options), allow the Java VNC Viewer applet to be downloaded
              thru the VNC port via HTTP.

              That is to say, you can use a single port for Java applet viewer
              connections by using a URL in your web browser  like  this,  for
              example:

              http://hostname:5900

              The   regular,  two-port  mode,  URL  http://hostname:5800  will
              continue to work as well.

              As mentioned above, this mode  will  NOT  work  with  the  -ssl,
              -stunnel,   or   -enc  encryption  options.   Note  that  is  it
              equivalent to '-enc none'  (i.e.  it  uses  the  same  detection
              mechanism as for HTTPS, but with no encryption.)

              HTTPS  single-port  is on by default in -ssl encrypted mode (and
              -enc too), so you only need  -http_oneport  when  doing  non-SSL
              encrypted connections.

              This  mode  could  also be useful for SSH tunnels since it means
              only one port needs to be redirected.

              The -httpsredir option may also be useful  for  this  mode  when
              using an SSH tunnel as well as for router port redirections.

              Note   that   the   -env  X11VNC_HTTP_LISTEN_LOCALHOST=1  option
              described above under -httpsredir applies for  the  LibVNCServer
              httpd server in all cases (ssl or not.)

       -ssh user@host:disp

              Create  a  remote  listening  port  on  machine "host" via a SSH
              tunnel using the -R rport:localhost:lport method. lport will  be
              the  local  x11vnc  listening  port,  so  a  connection to rport
              (5900+disp) on "host" will reach x11vnc.  E.g. fred@snoopy.com:0

              This could be useful  if  a  firewall/router  prevents  incoming
              connections  to  the  x11vnc machine, but the ssh machine "host"
              can be reached by the VNC viewer. "user@" is not  needed  unless
              the remote unix username differs from the current one.

              By  default the remote sshd is usually configured to listen only
              on localhost for rport, so the viewer may need to ssh  -L  redir
              to  "host"  as  well  (See  SSVNC  to  automate this).  The sshd
              setting GatewayPorts enables listening  on  all  interfaces  for
              rport; viewers can reach it more easily.

              "disp"  is  the  VNC  display  for  the  remote SSH side, e.g. 0
              corresponds to port 5900, etc.  If disp is greater than 200  the
              value  is used as the port.  Use a negative value to force a low
              port, e.g. host:-80 will use port 80.

              If ssh-agent is not active, then the ssh password  needs  to  be
              entered in the terminal where x11vnc is running.

              By  default  the remote ssh will issue a 'sleep 300' to wait for
              the  incoming  connection  for  5  mins.   To  modify  this  use
              user@host:disp+secs.

              If the remote SSH server is on a non-standard port (i.e. not 22)
              use user@host:port:disp+secs.

              Note that the ssh process MAY NOT be killed when  x11vnc  exits.
              It tries by looking at ps(1) output.

       -users list

              If  x11vnc is started as root (say from inetd(8) or from display
              managers xdm(1) , gdm(1) , etc), then as soon as possible  after
              connections  to  the  X display are established try to switch to
              one of the users in the comma separated list.  If x11vnc is  not
              running as root this option is ignored.

              Why  use  this option?  In general it is not needed since x11vnc
              is already connected to  the  X  display  and  can  perform  its
              primary  functions.   The  option  was added to make some of the
              *external*  utility  commands  x11vnc  occasionally  runs   work
              properly.   In  particular  under GNOME and KDE to implement the
              "-solid color" feature external commands (gconftool-2 and  dcop)
              unfortunately  must  be  run  as  the  user  owning  the desktop
              session.  Since this option switches userid it also affects  the
              userid  used  to  run  the  processes  for the -accept and -gone
              options.  It also affects the ability to read files for  options
              such  as  -connect,  -allow,  and  -remap and also the ultra and
              tight filetransfer feature if enabled.  Note that  the  -connect
              file is also sometimes written to.

              So  be careful with this option since in some situations its use
              can decrease security.

              In general the switch to a user will  only  take  place  if  the
              display  can  still be successfully opened as that user (this is
              primarily to try to guess the  actual  owner  of  the  session).
              Example: "-users fred,wilma,betty".  Note that a malicious local
              user "barney" by quickly using "xhost +"  when  logging  in  may
              possibly  get the x11vnc process to switch to user "fred".  What
              happens next?

              Under display managers it may be a long time before  the  switch
              succeeds  (i.e.  a  user  logs  in).   To instead make it switch
              immediately regardless if the display can be reopened prefix the
              username  with  the "+" character. E.g. "-users +bob" or "-users
              +nobody".

              The latter (i.e. switching immediately to user "nobody") is  the
              only obvious use of the -users option that increases security.

              Use  the  following  notation  to associate a group with a user:
              user1.group1,user2.group2,...   Note  that  initgroups(2)   will
              still be called first to try to switch to ALL of a user's groups
              (primary and additional groups).  Only if that fails  or  it  is
              not  available  then the single group specified as above (or the
              user's primary group if  not  specified)  is  switched  to  with
              setgid(2).   Use  -env  X11VNC_SINGLE_GROUP=1  to prevent trying
              initgroups(2) and only switch to the single group.  This sort of
              setting  is  only  really  needed  to  make  the  ultra or tight
              filetransfer permissions work properly. This format  applies  to
              any  comma  separated  list of users, even the special "=" modes
              described below.

              In -unixpw mode, if "-users unixpw=" is supplied  then  after  a
              user  authenticates  himself  via  the -unixpw mechanism, x11vnc
              will try to switch to that user as though "-users +username" had
              been  supplied.   If  you want to limit which users this will be
              done for, provide them as a comma separated list after "unixpw="
              Groups can also be specified as described above.

              Similarly,  in  -ssl mode, if "-users sslpeer=" is supplied then
              after an SSL client authenticates with his cert (the  -sslverify
              option is required for this) x11vnc will extract a UNIX username
              from the "emailAddress"  field  (username@hostname.com)  of  the
              "Subject"  of  the  x509 SSL cert and then try to switch to that
              user as though "-users +username" had  been  supplied.   If  you
              want to limit which users this will be done for, provide them as
              a comma separated list  after  "sslpeer=".   Set  the  env.  var
              X11VNC_SSLPEER_CN  to  use the Common Name (normally a hostname)
              instead of the Email field.

              NOTE: for sslpeer= mode the x11vnc administrator must take  care
              that  any  client  certs he adds to -sslverify have the intended
              UNIX  username  in  the  "emailAddress"  field  of   the   cert.
              Otherwise a user may be able to log in as another.  This command
              can be of use in checking: "openssl x509  -text  -in  file.crt",
              see the "Subject:" line.  Also, along with the normal RFB_* env.
              vars.  (see  -accept)  passed   to   external   cmd=   commands,
              RFB_SSL_CLIENT_CERT will be set to the client's x509 certificate
              string.

              The sslpeer= mode can aid finding X sessions via the FINDDISPLAY
              and FINDCREATEDISPLAY mechanisms.

              To  immediately  switch  to a user *before* connections to the X
              display are made or any files  opened  use  the  "="  character:
              "-users =bob".  That user needs to be able to open the X display
              and any files of course.

              The special user "guess=" means to examine  the  utmpx  database
              (see  who(1) ) looking for a user attached to the display number
              (from DISPLAY or -display option) and try him/her.  To limit the
              list of guesses, use: "-users guess=bob,betty".

              Even more sinister is the special user "lurk=" that means to try
              to guess the DISPLAY from the utmpx login database as well.   So
              it  "lurks" waiting for anyone to log into an X session and then
              connects to it.  Specify a list of users after the  =  to  limit
              which  users  will  be  tried.   To enable a different searching
              mode, if the first user in the list is something  like  ":0"  or
              ":0-2"  that  indicates  a range of DISPLAY numbers that will be
              tried (regardless of whether they are in the utmpx database) for
              all  users that are logged in.  Also see the "-display WAIT:..."
              functionality.   Examples:  "-users  lurk="  and  also   "-users
              lurk=:0-1,bob,mary"

              Be  especially  careful  using  the  "guess=" and "lurk=" modes.
              They are not recommended for use on machines with  untrustworthy
              local users.

       -noshm

              Do  not  use  the  MIT-SHM  extension  for  the polling.  Remote
              displays can be polled this way: be careful this can  use  large
              amounts  of network bandwidth.  This is also of use if the local
              machine has a limited number of shm segments and -onetile is not
              sufficient.

       -flipbyteorder

              Sometimes   needed   if   remotely  polled  host  has  different
              endianness.  Ignored unless -noshm is set.

       -onetile

              Do not use the new copy_tiles() framebuffer mechanism, just  use
              1 shm tile for polling.  Limits shm segments used to 3.

              To  disable  any  automatic  shm  reduction  set  the  env. var.
              X11VNC_NO_LIMIT_SHM.

       -solid [color]

              To improve performance, when VNC clients are  connected  try  to
              change  the desktop background to a solid color.  The [color] is
              optional: the default color is "cyan4".   For  a  different  one
              specify  the X color (rgb.txt name, e.g. "darkblue" or numerical
              "#RRGGBB").

              Currently this option only works on GNOME, KDE, CDE,  XFCE,  and
              classic  X  (i.e. with the background image on the root window).
              The "gconftool-2", "dcop" and "xfconf-query"  external  commands
              are  run for GNOME, KDE, and XFCE respectively.  This also works
              on native MacOSX.  (There is no color selection  for  MacOSX  or
              XFCE.)   Other  desktops  won't work, (send us the corresponding
              commands if you find them).  If x11vnc  is  running  as  root  (
              inetd(8) or gdm(1) ), the -users option may be needed for GNOME,
              KDE, XFCE.  If x11vnc guesses your desktop incorrectly, you  can
              force  it  by  prefixing  color  with  "gnome:", "kde:", "cde:",
              "xfce:", or "root:".

              Update: -solid no longer works on KDE4.

              This mode works in a limited way on the Mac OS  X  Console  with
              one   color  ('kelp')  using  the  screensaver  writing  to  the
              background.    Look    in    "~/Library/Screen    Savers"    for
              VncSolidColor.png to change the color.

       -blackout string

              Black  out rectangles on the screen. string is a comma separated
              list of WxH+X+Y type geometries for each rectangle.  If  one  of
              the  items  on  the list is the string "noptr" the mouse pointer
              will not be allowed to go into a blacked out region.

       -xinerama, -noxinerama

              If your screen is composed of multiple monitors  glued  together
              via  XINERAMA,  and  that  screen is not a rectangle this option
              will try to guess the areas to black out  (if  your  system  has
              libXinerama).  default: -xinerama

              In general, we have noticed on XINERAMA displays you may need to
              use the "-xwarppointer" option if the mouse  pointer  misbehaves
              and  it  is  enabled by default. Use "-noxwarppointer" if you do
              not want this.

       -xtrap

              Use the  DEC-XTRAP  extension  for  keystroke  and  mouse  input
              insertion.   For  use  on legacy systems, e.g. X11R5, running an
              incomplete or missing XTEST  extension.   By  default  DEC-XTRAP
              will be used if XTEST server grab control is missing, use -xtrap
              to do the keystroke and mouse insertion via DEC-XTRAP as well.

       -xrandr [mode]

              If the  display  supports  the  XRANDR  (X  Resize,  Rotate  and
              Reflection)  extension, and you expect XRANDR events to occur to
              the display while x11vnc  is  running,  this  options  indicates
              x11vnc  should  try  to  respond  to  them (as opposed to simply
              crashing by assuming the old screen size).   See  the  xrandr(1)
              manpage  and  run ´xrandr -q' for more info.  [mode] is optional
              and described below.

              Since watching for XRANDR events and trapping  errors  increases
              polling  overhead,  only  use  this option if XRANDR changes are
              expected.  For example on a rotatable screen PDA or  laptop,  or
              using a XRANDR-aware Desktop where you resize often.  It is best
              to be viewing with  a  vncviewer  that  supports  the  NewFBSize
              encoding,  since  it  knows how to react to screen size changes.
              Otherwise, LibVNCServer tries to do so something reasonable  for
              viewers  that  cannot  do  this  (portions  of the screen may be
              clipped, unused, etc).

              Note: the default now is to check for XRANDR events, but do  not
              trap  every  X  call  that  may fail due to resize.  If a resize
              event is received, the full -xrandr mode is enabled.  To disable
              even checking for events supply: -noxrandr.

              "mode"  defaults to "resize", which means create a new, resized,
              framebuffer and hope all  viewers  can  cope  with  the  change.
              "newfbsize"  means  first  disconnect  all  viewers  that do not
              support  the  NewFBSize  VNC  encoding,  and  then  resize   the
              framebuffer.   "exit"  means  disconnect all viewer clients, and
              then terminate x11vnc.

       -rotate string

              Rotate and/or flip the framebuffer view exported by  VNC.   This
              transformation  is independent of XRANDR and is done in software
              in main memory and so may be slower.  This mode could be  useful
              on  a  handheld  with  portrait  or  landscape modes that do not
              correspond to the scanline  order  of  the  actual  framebuffer.
              string can be:

              x      flip  along  x-axis  y      flip along y-axis xy     flip
              along x- and y-axes +90      rotate  90  degrees  clockwise  -90
              rotate  90  degrees counter-clockwise +90x     rotate 90 degrees
              CW, then flip along x +90y     rotate 90 degrees CW,  then  flip
              along y

              these give all possible rotations and reflections.

              Aliases: same as xy:  yx, +180, -180, 180 same as -90: +270, 270
              same as +90: 90, (ditto for 90x, 90y)

              Like -scale, this transformation is applied at the very  end  of
              any chain of framebuffer transformations and so any options with
              geometries, e.g. -blackout, -clip, etc.   are  relative  to  the
              original  X  (or  -rawfb) framebuffer, not the final one sent to
              VNC viewers.

              If you do not want the cursor shape to be rotated prefix  string
              with "nc:", e.g. "nc:+90", "nc:xy", etc.

       -padgeom WxH

              Whenever  a  new vncviewer connects, the framebuffer is replaced
              with  a  fake,  solid  black  one  of  geometry  WxH.    Shortly
              afterwards  the framebuffer is replaced with the real one.  This
              is  intended  for  use  with  vncviewers  that  do  not  support
              NewFBSize and one wants to make sure the initial viewer geometry
              will be big enough to handle all subsequent resizes (e.g.  under
              -xrandr, -remote id:windowid, rescaling, etc.)

              In  -unixpw  mode  this  sets the size of the login screen.  Use
              "once:WxH" it ignore padgeom after the login screen is set up.

       -o logfile

              Write  stderr  messages  to  file  logfile  instead  of  to  the
              terminal.   Same  as "-logfile file".  To append to the file use
              "-oa file" or "-logappend file".  If logfile contains the string
              "%VNCDISPLAY"  it  is  expanded to the vnc display (the name may
              need to be guessed at.)  "%HOME" works too.

       -flag file

              Write  the  "PORT=NNNN"  (e.g.  PORT=5900)  string  to  file  in
              addition  to  stdout.   This  option  could be useful by wrapper
              script to detect when x11vnc is ready.

       -rmflag file

              Remove file at exit to signal when x11vnc is done.  The file  is
              created  at  startup  if it does not already exist or if file is
              prefixed with "create:".  If the file is created, the x11vnc PID
              is  placed  in  the  file.   Otherwise the files contents is not
              changed.  Use prefix "nocreate:" to prevent creation.

       -rc filename

              Use filename instead of $HOME/.x11vncrc for rc file.

       -norc

              Do not process any .x11vncrc file for options.

       -env VAR=VALUE

              Set the environment variable 'VAR' to value  'VALUE'  at  x11vnc
              startup.   This  is  a convenience utility to avoid shell script
              wrappers, etc. to set the env. var.  You may specify as many  of
              these as needed on the command line.

       -prog /path/to/x11vnc

              Set the full path to the x11vnc program for cases when it cannot
              be determined from argv[0] (e.g. tcpd/inetd)

       -h, -help

              Print this help text.   -?,  -opts               Only  list  the
              x11vnc options.

       -V, -version

              Print program version and last modification date.

       -license

              Print out license information.  Same as -copying and -warranty.

       -dbg

              Instead  of exiting after cleaning up, run a simple "debug crash
              shell" when fatal errors are trapped.

       -q, -quiet

              Be quiet by printing less informational output to  stderr.  (use
              -noquiet to undo an earlier -quiet.)

              The  -quiet  option does not eliminate all informational output,
              it only reduces it.  It  is  ignored  in  most  auxiliary  usage
              modes,   e.g.   -storepasswd.   To  eliminate  all  output  use:
              2>/dev/null 1>&2, etc.

       -v, -verbose

              Print out more information to stderr.

       -bg

              Go into the background after screen setup.  Messages  to  stderr
              are  lost  unless -o logfile is used.  Something like this could
              be useful in a script:

              port=`ssh -t $host "x11vnc -display :0 -bg" | grep PORT`

              port=`echo "$port" | sed -e 's/PORT=//'`

              port=`expr $port - 5900`

              vncviewer $host:$port

       -modtweak, -nomodtweak

              Option -modtweak automatically tries to  adjust  the  AltGr  and
              Shift  modifiers for differing language keyboards between client
              and host.  Otherwise, only  a  single  key  press/release  of  a
              Keycode  is simulated (i.e. ignoring the state of the modifiers:
              this usually works for identical  keyboards).   Also  useful  in
              resolving  cases  where a Keysym is bound to multiple keys (e.g.
              "<" + ">" and "," + "<" keys).  Default: -modtweak

              If you are having trouble with with keys and -xkb or -noxkb, and
              similar things don't help, try -nomodtweak.

              On  some  HP-UX  systems  it is been noted that they have an odd
              keymapping where a single keycode will have a keysym, e.g.  "#",
              up  to  three times.  You can check via "xmodmap -pk" or the -dk
              option.  The failure is when you try to type "#" it yields  "3".
              If  you  see  this  problem try setting the environment variable
              MODTWEAK_LOWEST=1 to see if it helps.

       -xkb, -noxkb

              When in modtweak mode, use the XKEYBOARD  extension  (if  the  X
              display  supports  it)  to  do  the  modifier tweaking.  This is
              powerful and should be  tried  if  there  are  still  keymapping
              problems  when  using  -modtweak  by  itself.  The default is to
              check whether some common  keysyms,  e.g.  !,  @,  [,  are  only
              accessible via -xkb mode and if so then automatically enable the
              mode.  To disable this automatic detection use -noxkb.

              When -xkb mode is active you can  set  these  env.  vars.   They
              apply  only  when  there  is ambiguity as to which key to choose
              (i.e the mapping is not one-to-one).  NOKEYHINTS=1: for up ascii
              keystrokes do not use score hints saved when the key was pressed
              down. NOANYDOWN=1: for up keystrokes do not resort to  searching
              through  keys  that  are  currently  pressed  down.  KEYSDOWN=N:
              remember the last N keys press down for tie-breaking when an  up
              keystroke comes in.

       -capslock

              When in -modtweak (the default) or -xkb mode, if a keysym in the
              range A-Z comes in check the X server to see if the Caps_Lock is
              set.   If  it is do not artificially press Shift to generate the
              keysym.  This will enable the CapsLock key to  behave  correctly
              in  some circumstances: namely *both* the VNC viewer machine and
              the x11vnc X server are in the CapsLock on state.  If  one  side
              has  CapsLock  on  and  the  other  off  and the keyboard is not
              behaving as you think it should you should correct the  CapsLock
              states (hint: pressing CapsLock inside and outside of the viewer
              can help toggle them both to the correct state).   However,  for
              best  results  do  not use this option, but rather *only* enable
              CapsLock on the VNC  viewer  side  (i.e.  by  pressing  CapsLock
              outside  of the viewer window, also -skip_lockkeys below).  Also
              try -nomodtweak for a possible workaround.

       -skip_lockkeys, -noskip_lockkeys

              Have  x11vnc  ignore  all   Caps_Lock,   Shift_Lock,   Num_Lock,
              Scroll_Lock  keysyms  received  from  viewers.   The idea is you
              press Caps_Lock on the VNC Viewer side but that does not  change
              the  lock  state in the x11vnc-side X server.  Nevertheless your
              capitalized letters come  in  over  the  wire  and  are  applied
              correctly  to the x11vnc-side X server.  Note this mode probably
              won't do what you want in -nomodtweak mode.  Also, a kludge  for
              KP_n  digits  is  always  done  in this mode: they are mapped to
              regular digit keysyms.  See also -capslock above.   The  default
              is -noskip_lockkeys.

       -skip_keycodes string

              Ignore  the  comma  separated list of decimal keycodes.  Perhaps
              these are keycodes not on your keyboard but your X server thinks
              exist.  Currently only applies to -xkb mode.  Use this option to
              help x11vnc in the reverse problem it tries to solve: Keysym  ->
              Keycode(s)  when  ambiguities  exist  (more than one Keycode per
              Keysym).  Run 'xmodmap -pk' to see  your  keymapping.   Example:
              "-skip_keycodes 94,114"

       -sloppy_keys

              Experimental  option  that  tries  to  correct some "sloppy" key
              behavior.  E.g. if at the viewer you press  Shift+Key  but  then
              release  the  Shift  before  Key  that  could give rise to extra
              unwanted characters (usually only between keyboards of different
              languages).   Only  use this option if you observe problems with
              some keystrokes.

       -skip_dups, -noskip_dups

              Some VNC viewers send impossible repeated key events, e.g.  key-
              down, key-down, key-up, key-up all for the same key, or 20 downs
              in a row for the same modifier key!  Setting -skip_dups means to
              skip  these  duplicates  and just process the first event. Note:
              some VNC  viewers  assume  they  can  send  down's  without  the
              corresponding  up's  and  so  you should not set this option for
              these viewers (symptom: some keys do  not  autorepeat)  Default:
              -noskip_dups

       -add_keysyms, -noadd_keysyms

              If  a  Keysym is received from a VNC viewer and that Keysym does
              not exist in the X server, then add the Keysym to the X server's
              keyboard  mapping  on  an  unused  key.   Added  Keysyms will be
              removed periodically  and  also  when  x11vnc  exits.   Default:
              -add_keysyms

       -clear_mods

              At   startup  and  exit  clear  the  modifier  keys  by  sending
              KeyRelease for each one. The Lock modifiers are  skipped.   Used
              to clear the state if the display was accidentally left with any
              pressed down.

       -clear_keys

              As -clear_mods, except try to release  ANY  pressed  key.   Note
              that  this  option  and  -clear_mods can interfere with a person
              typing at the physical keyboard.

       -clear_all

              As -clear_keys, except try to  release  any  CapsLock,  NumLock,
              etc. locks as well.

       -remap string

              Read  Keysym  remappings  from file named string.  Format is one
              pair of Keysyms per line (can be name or hex value) separated by
              a  space.   If  no  file  named  string  exists,  it  is instead
              interpreted   as   this   form:   key1-key2,key3-key4,...    See
              <X11/keysymdef.h> header file for a list of Keysym names, or use
              xev(1).

              To map a key to a button click, use the fake Keysyms  "Button1",
              ..., etc. E.g: "-remap Super_R-Button2" (useful for pasting on a
              laptop)

              I use these if the machine I am viewing from  does  not  have  a
              scrollwheel or I don't like using the one it has:

              -remap      Super_R-Button4,Menu-Button5      -remap     KP_Add-
              Button4,KP_Enter-Button5

              the former would be used on a PC, the latter on a MacBook.  This
              way  those  little used keys can be used to generate bigger hops
              than the Up and Down arrows provide.   One  can  scroll  through
              text  or  web  pages more quickly this way (especially if x11vnc
              scroll detection is active.)

              Use Button44, Button12, etc. for multiple clicks.

              To disable a keysym (i.e. make it so it will not  be  injected),
              remap it to "NoSymbol" or "None".

              Dead  keys:  "dead"  (or silent, mute) keys are keys that do not
              produce a character but must be followed  by  a  2nd  keystroke.
              This  is often used for accenting characters, e.g. to put "`" on
              top of "a" by pressing the dead key and  then  "a".   Note  that
              this  interpretation  is  not  part of core X11, it is up to the
              toolkit or application to decide how to react to  the  sequence.
              The  X11 names for these keysyms are "dead_grave", "dead_acute",
              etc.  However some VNC viewers send the keysyms "grave", "acute"
              instead  thereby  disabling  the accenting.  To work around this
              -remap can be used.  For example "-remap grave-dead_grave,acute-
              dead_acute"

              As a convenience, "-remap DEAD" applies these remaps:

                    g     grave-dead_grave
                    a     acute-dead_acute
                    c     asciicircum-dead_circumflex
                    t     asciitilde-dead_tilde
                    m     macron-dead_macron
                    b     breve-dead_breve
                    D     abovedot-dead_abovedot
                    d     diaeresis-dead_diaeresis
                    o     degree-dead_abovering
                    A     doubleacute-dead_doubleacute
                    r     caron-dead_caron
                    e     cedilla-dead_cedilla

              If  you  just  want  a  subset  use the first letter label, e.g.
              "-remap DEAD=ga" to get the first two.   Additional  remaps  may
              also  be  supplied  via  commas,  e.g.  "-remap DEAD=ga,Super_R-
              Button2".  Finally, "DEAD=missing" means to  apply  all  of  the
              above  as long as the left hand member is not already in the X11
              keymap.

       -norepeat, -repeat

              Option -norepeat disables X server  key  auto  repeat  when  VNC
              clients  are  connected  and  VNC keyboard input is not idle for
              more than 5 minutes.  This works around a  repeating  keystrokes
              bug  (triggered  by  long processing delays between key down and
              key up client events: either from large screen changes  or  high
              latency).  Default: -norepeat

              You  can  set the env. var. X11VNC_IDLE_TIMEOUT to the number of
              idle seconds you want (5min = 300secs).

              Note: your VNC viewer side will likely do autorepeating, so this
              is  no  loss  unless  someone  is  simultaneously  at the real X
              display.

              Use "-norepeat N" to set how many times norepeat will  be  reset
              if  something  else  (e.g.  X  session  manager) undoes it.  The
              default is 2.  Use a negative value for unlimited resets.

       -nofb

              Ignore video framebuffer: only  process  keyboard  and  pointer.
              Intended for use with Win2VNC and x2vnc dual-monitor setups.

       -nobell

              Do  not  watch  for XBell events. (no beeps will be heard) Note:
              XBell monitoring requires the XKEYBOARD extension.

       -nosel

              Do not manage exchange  of  X  selection/cutbuffer  between  VNC
              viewers and the X server at all.

       -noprimary

              Do  not  poll  the PRIMARY selection for changes to send back to
              clients.  (PRIMARY is still set on received changes, however).

       -nosetprimary

              Do not set the PRIMARY selection for changes received  from  VNC
              clients.

       -noclipboard

              Do  not poll the CLIPBOARD selection for changes to send back to
              clients.  (CLIPBOARD is still set on received changes, however).

       -nosetclipboard

              Do not set the CLIPBOARD selection for changes received from VNC
              clients.

       -seldir string

              If  direction  string  is  "send",  only  send  the selection to
              viewers, and if it is "recv" only receive it from  viewers.   To
              work  around  apps  setting  the  selection  too  frequently and
              messing up the other end.   You  can  actually  supply  a  comma
              separated  list  of  directions,  including  "debug"  to turn on
              debugging output.

       -cursor [mode], -nocursor

              Sets how the pointer cursor shape  (little  icon  at  the  mouse
              pointer)  should  be handled.  The "mode" string is optional and
              is described below.  The default is to show some sort of  cursor
              shape(s).   How this is done depends on the VNC viewer and the X
              server.  Use -nocursor to disable cursor shapes completely.

              Some VNC  viewers  support  the  TightVNC  CursorPosUpdates  and
              CursorShapeUpdates  extensions  (cuts down on network traffic by
              not having to send the cursor image every time  the  pointer  is
              moved),   in   which   case   these  extensions  are  used  (see
              -nocursorshape and -nocursorpos below to  disable).   For  other
              viewers  the cursor shape is written directly to the framebuffer
              every time the pointer is moved or changed and gets  sent  along
              with the other framebuffer updates.  In this case, there will be
              some lag between the vnc viewer pointer and  the  remote  cursor
              position.

              If   the   X   display  supports  retrieving  the  cursor  shape
              information from the X server, then the default is to  use  that
              mode.   On  Solaris  this can be done with the SUN_OVL extension
              using -overlay  (see  also  the  -overlay_nocursor  option).   A
              similar  overlay  scheme is used on IRIX.  Xorg (e.g. Linux) and
              recent Solaris Xsun servers  support  the  XFIXES  extension  to
              retrieve the exact cursor shape from the X server.  If XFIXES is
              present it is preferred over Overlay and is used by default (see
              -noxfixes below).  This can be disabled with -nocursor, and also
              some values of the "mode" option below.

              Note that under XFIXES cursors with transparency (alpha channel)
              will usually not be exactly represented and one may find Overlay
              preferable.  See also the -alphacut and -alphafrac options below
              as  fudge  factors  to  try to improve the situation for cursors
              with transparency for a given theme.

              The "mode" string can be used to  fine-tune  the  displaying  of
              cursor shapes.  It can be used the following ways:

              "-cursor  arrow"  - just show the standard arrow nothing more or
              nothing less.

              "-cursor none" - same as "-nocursor"

              "-cursor X" - when the cursor appears to be on the root  window,
              draw the familiar X shape.  Some desktops such as GNOME cover up
              the root window completely, and so this will not work, try "X1",
              etc,  to  try to shift the tree depth.  On high latency links or
              slow machines there will be a time lag between expected and  the
              actual cursor shape.

              "-cursor  some"  - like "X" but use additional heuristics to try
              to guess if the window should have a windowmanager-like  resizer
              cursor  or a text input I-beam cursor.  This is a complete hack,
              but may be useful in  some  situations  because  it  provides  a
              little more feedback about the cursor shape.

              "-cursor most" - try to show as many cursors as possible.  Often
              this will only be the same as  "some"  unless  the  display  has
              overlay  visuals or XFIXES extensions available.  On Solaris and
              IRIX  if  XFIXES  is  not  available,  -overlay  mode  will   be
              attempted.

       -cursor_drag

              Show  cursor  shape changes even when the mouse is being dragged
              with a mouse button down.  This is useful if you want to be able
              to see Drag-and-Drop cursor icons, etc.

       -arrow n

              Choose  an  alternate  "arrow"  cursor from a set of some common
              ones.  n can be 1 to 6.  Default is: 1 Ignored  when  in  XFIXES
              cursor-grabbing mode.

       -noxfixes

              Do  not  use the XFIXES extension to draw the exact cursor shape
              even if it is available.

              Note: To work around a crash in Xorg 1.5 and later  some  people
              needed  to use -noxfixes.  The Xorg crash occurred right after a
              Display Manager (e.g. GDM) login.  Starting with x11vnc 0.9.9 it
              tries  to  automatically  avoid  using XFIXES until it is sure a
              window manager is running.  See the -reopen option for more info
              and how to use X11VNC_AVOID_WINDOWS=never to disable it.

       -alphacut n

              When  using  the  XFIXES extension for the cursor shape, cursors
              with transparency will not usually  be  displayed  exactly  (but
              opaque  ones  will).  This option sets n as a cutoff for cursors
              that have transparency ("alpha channel" with values ranging from
              0  to 255) Any cursor pixel with alpha value less than n becomes
              completely  transparent.   Otherwise  the  pixel  is  completely
              opaque.  Default 240

       -alphafrac fraction

              With  the threshold in -alphacut some cursors will become almost
              completely transparent because their alpha values are  not  high
              enough.   For  those  cursors  adjust  the alpha threshold until
              fraction of the non-zero alpha  channel  pixels  become  opaque.
              Default 0.33

       -alpharemove

              By  default,  XFIXES  cursors  pixels with transparency have the
              alpha factor multiplied into the RGB  color  values  (i.e.  that
              corresponding  to  blending the cursor with a black background).
              Specify this option to remove  the  alpha  factor.  (useful  for
              light colored semi-transparent cursors).

       -noalphablend

              In  XFIXES  mode  do  not  send  cursor  alpha  channel  data to
              LibVNCServer.  The default is to send it.  The alphablend effect
              will  only be visible in -nocursorshape mode or for clients with
              cursorshapeupdates turned off. (However  there  is  a  hack  for
              32bpp  with  depth  24, it uses the extra 8 bits to store cursor
              transparency for use with a hacked vncviewer  that  applies  the
              transparency locally.  See the FAQ for more info).

       -nocursorshape

              Do  not  use  the  TightVNC CursorShapeUpdates extension even if
              clients support it.  See -cursor above.

       -cursorpos, -nocursorpos

              Option -cursorpos enables sending the X cursor position back  to
              all  vnc  clients  that  support  the  TightVNC CursorPosUpdates
              extension.  Other clients  will  be  able  to  see  the  pointer
              motions. Default: -cursorpos

       -xwarppointer, -noxwarppointer

              Move  the  pointer  with  XWarpPointer(3X)  instead of the XTEST
              extension.  Use this as  a  workaround  if  the  pointer  motion
              behaves incorrectly, e.g.  on touchscreens or other non-standard
              setups.

              It is also sometimes needed on XINERAMA displays and is  enabled
              by  default if XINERAMA is found to be active.  To prevent this,
              use -noxwarppointer.

       -always_inject

              Even if there is no displacement (dx = dy = 0) for a  VNC  mouse
              event  force  the  pointer to the indicated x,y position anyway.
              Recent (2009) gui toolkits (gnome) have problems  with  x11vnc's
              original  mouse input injection method.  So x11vnc's mouse input
              injection method has been modified.  To regain the OLD  behavior
              use  this option: -always_inject.  Then x11vnc will always force
              positioning the mouse to the x,y position even if that  position
              has not changed since the previous VNC input event.

              The  first place this problem was noticed was in gnome terminal:
              if you pressed and released mouse button 3, a  menu  was  posted
              and  then its first element 'New Terminal Window' was activated.
              This was because x11vnc injected the mouse position twice:  once
              on   ButtonPress   and  again  on  ButtonRelease.   The  toolkit
              interpreted the 2nd one as mouse motion even  though  the  mouse
              hadn't moved.  So now by default x11vnc tries to avoid injecting
              the 2nd one.

              Note that with the new  default  x11vnc  will  be  oblivious  to
              applications  moving  the  pointer  (warping) or the user at the
              physical  display  moving  it.   So  it  might,   e.g.,   inject
              ButtonRelease  at  the  wrong  position.   If  this  (or similar
              scenarios)  causes  problems  in   your   environment,   specify
              -always_inject for the old method.

       -buttonmap string

              String  to  remap  mouse  buttons.   Format:  IJK-LMN, this maps
              buttons I -> L, etc., e.g.  -buttonmap 13-31

              Button presses can also  be  mapped  to  keystrokes:  replace  a
              button   digit  on  the  right  of  the  dash  with  :<sym>:  or
              :<sym1>+<sym2>: etc. for multiple  keys.  For  example,  if  the
              viewing  machine  has a mouse-wheel (buttons 4 5) but the x11vnc
              side does not, these will do scrolls:

              -buttonmap 12345-123:Prior::Next:

              -buttonmap 12345-123:Up+Up+Up::Down+Down+Down:

              See <X11/keysymdef.h> header file for a list of Keysyms, or  use
              the  xev(1)  program.  Note: mapping of button clicks to Keysyms
              may not work if -modtweak or -xkb is needed for the Keysym.

              If you include a modifier like "Shift_L" the modifier's  up/down
              state is toggled, e.g. to send "The" use :Shift_L+t+Shift_L+h+e:
              (the 1st one is shift down and the 2nd one is shift up).  (note:
              the  initial  state of the modifier is ignored and not reset) To
              include button events use "Button1", ... etc.

              -buttonmap currently does not  work  on  MacOSX  console  or  in
              -rawfb mode.

              Workaround:  use -buttonmap IJ...-LM...=n to limit the number of
              mouse buttons to n, e.g. 123-123=3.  This  will  prevent  x11vnc
              from  crashing  if the X server reports there are 5 buttons (4/5
              scroll wheel), but there are only really 3.

       -nodragging

              Do not update the display during mouse  dragging  events  (mouse
              button  held  down).   Greatly improves response on slow setups,
              but you lose all visual feedback for drags, text selection,  and
              some menu traversals.  It overrides any -pointer_mode setting.

       -ncache n

              Client-side  caching  scheme.  Framebuffer memory n (an integer)
              times that of the full display is  allocated  below  the  actual
              framebuffer  to cache screen contents for rapid retrieval.  So a
              W x H frambuffer is expanded to a W x (n+1)*H  one.   Use  0  to
              disable.

              The n is actually optional, the default is 10.

              For this and the other -ncache* options below you can abbreviate
              "-ncache" with "-nc".  Also, "-nonc" is the same as "-ncache 0"

              This is an experimental  option,  currently  implemented  in  an
              awkward  way  in  that  in  the VNC Viewer you can see the pixel
              cache contents if you scroll down, etc.  So you will have to set
              things  up  so  you  can't  see  that region.  If this method is
              successful, the changes required for clients  to  do  this  less
              awkwardly will be investigated.

              The  SSVNC  viewer  does  a good job at automatically hiding the
              pixel cache region.  Or use SSVNC's -ycrop option to  explicitly
              hide the region.

              Note  that  this  mode consumes a huge amount of memory, both on
              the x11vnc server side and on the VNC Viewer side.  If n=2  then
              the  amount  of  RAM used is roughly tripled for both x11vnc and
              the VNC Viewer.  As a rule of  thumb,  note  that  1280x1024  at
              depth 24 is about 5MB of pixel data.

              For  reasonable response when cycling through 4 to 6 large (e.g.
              web browser) windows a value  n  of  6  to  12  is  recommended.
              (that's right: ~10X more memory...)

              Because  of  the  way  window  backingstore  and  saveunders are
              implemented, n must be even.  It will be incremented by 1 if  it
              is not.

              This  mode  also  works  for  native  MacOS X, but may not be as
              effective as the X version.  This is due to a number of  things,
              one  is the drop-shadow compositing that leaves extra areas that
              need to be repaired (see -ncache_pad).  Another  is  the  window
              iconification  animations need to be avoided (see -macicontime).
              It appears the that the  'Scale'  animation  mode  gives  better
              results  than the 'Genie' one.  Also, window event detection not
              as accurate as the X version.

       -ncache_cr

              In -ncache mode, try to do copyrect  opaque  window  moves/drags
              instead  of  wireframes  (this can induce painting errors).  The
              wireframe will still be used when moving a  window  whose  save-
              unders has not yet been set or has been invalidated.

              Some  VNC  Viewers provide better response than others with this
              option.  On Unix,  realvnc  viewer  gives  smoother  drags  than
              tightvnc viewer.  Response may also be choppy if the server side
              machine is too slow.

              Sometimes on very slow modem connections, this actually gives an
              improvement  because  no  pixel  data  at  all (not even the box
              animation) is sent during the drag.

       -ncache_no_moveraise

              In -ncache mode, do not assume that moving a window  will  cause
              the  window  manager  to  raise it to the top of the stack.  The
              default is to assume it does, and so at  the  beginning  of  any
              wireframe, etc, window moves the window will be pushed to top in
              the VNC viewer.

       -ncache_no_dtchange

              In -ncache mode, do not try to guess when the desktop (viewport)
              changes  to another one (i.e. another workarea).  The default is
              to try to guess and when detected try to  make  the  transistion
              more smoothly.

       -ncache_no_rootpixmap

              In  -ncache  mode, do not try to snapshot the desktop background
              to use in guessing or reconstructing window save-unders.

       -ncache_keep_anims

              In -ncache mode, do not try to disable window manager animations
              and  other  effects  (that usually degrade ncache performance or
              cause painting errors).  The default is to try to  disable  them
              on KDE (but not GNOME) when VNC clients are connected.

              For  other  window managers or desktops that provide animations,
              effects, compositing, translucency, etc. that interfere with the
              -ncache method you will have to disable them manually.

       -ncache_old_wm

              In  -ncache  mode,  enable  some heuristics for old style window
              managers such as fvwm and twm.

       -ncache_pad n

              In -ncache mode, pad each window with n pixels for  the  caching
              rectangles.   This  can  be used to try to improve the situation
              with dropshadows or  other  compositing  (e.g.  MacOS  X  window
              manager), although it could make things worse.  The default is 0
              on Unix and 24 on MacOS X.

       -debug_ncache

              Turn on debugging and profiling output under -ncache.

       -wireframe [str], -nowireframe

              Try to detect window moves or resizes when  a  mouse  button  is
              held  down  and  show  a  wireframe  instead  of the full opaque
              window.  This is based completely  on  heuristics  and  may  not
              always  work: it depends on your window manager and even how you
              move things around.  See -pointer_mode below for  discussion  of
              the  "bogging  down"  problem  this  tries  to  avoid.  Default:
              -wireframe

              Shorter aliases:  -wf [str]  and -nowf

              The value "str" is optional and, of course, is packed with  many
              tunable parameters for this scheme:

              Format: shade,linewidth,percent,T+B+L+R,mod,t1+t2+t3+t4 Default:
              0xff,2,0,32+8+8+8,all,0.15+0.30+5.0+0.125

              If you leave nothing between commas: ",," the default  value  is
              used.    If  you  don't  specify  enough  commas,  the  trailing
              parameters are set to their defaults.

              "shade" indicate  the  "color"  for  the  wireframe,  usually  a
              greyscale:  0-255,  however  for 16 and 32bpp you can specify an
              rgb.txt X color (e.g. "dodgerblue") or a value > 255 is  treated
              as  RGB  (e.g.  red is 0xff0000).  "linewidth" sets the width of
              the wireframe in pixels.  "percent" indicates to not  apply  the
              wireframe  scheme to windows with area less than this percent of
              the full screen.

              "T+B+L+R" indicates four integers for how close  in  pixels  the
              pointer  has to be from the Top, Bottom, Left, or Right edges of
              the window to  consider  wireframing.   This  is  a  speedup  to
              quickly  exclude a window from being wireframed: set them all to
              zero to not try the speedup (scrolling and selecting  text  will
              likely be slower).

              "mod"  specifies  if  a button down event in the interior of the
              window with a  modifier  key  (Alt,  Shift,  etc.)  down  should
              indicate  a  wireframe  opportunity.  It can be "0" or "none" to
              skip it, "1" or "all" to apply it to any modifier,  or  "Shift",
              "Alt",  "Control", "Meta", "Super", or "Hyper" to only apply for
              that type of modifier key.

              "t1+t2+t3+t4" specify four floating point times in  seconds:  t1
              is  how  long to wait for the pointer to move, t2 is how long to
              wait for the window to start moving or being resized  (for  some
              window managers this can be rather long), t3 is how long to keep
              a wireframe moving before  repainting  the  window.  t4  is  the
              minimum  time between sending wireframe "animations".  If a slow
              link is detected, these values may be automatically  changed  to
              something better for a slow link.

       -nowireframelocal

              By default, mouse motion and button presses of a user sitting at
              the LOCAL display are monitored  for  wireframing  opportunities
              (so  that  the  changes  will  be  sent  efficiently  to the VNC
              clients).  Use this option to disable this behavior.

       -wirecopyrect mode, -nowirecopyrect

              Since the -wireframe mechanism evidently tracks  moving  windows
              accurately, a speedup can be obtained by telling the VNC viewers
              to locally copy the translated window region.  This is  the  VNC
              CopyRect  encoding:  the framebuffer update doesn't need to send
              the actual new image data.

              Shorter aliases:  -wcr [mode]  and -nowcr

              "mode" can be "never" (same as -nowirecopyrect) to never try the
              copyrect,  "top"  means only do it if the window was not covered
              by any other  windows,  and  "always"  means  to  translate  the
              orginally  unobscured region (this may look odd as the remaining
              pieces come in, but helps on a slow link).  Default: "always"

              Note: there can be painting errors or slow response  when  using
              -scale  so  you  may  want  to  disable  CopyRect  in  this case
              "-wirecopyrect never" on the command line or by  remote-control.
              Or you can also use the "-scale xxx:nocr" scale option.

       -debug_wireframe

              Turn  on  debugging  info printout for the wireframe heuristics.
              "-dwf" is an alias.  Specify multiple times for more output.

       -scrollcopyrect mode, -noscrollcopyrect

              Like -wirecopyrect, but use heuristics to  try  to  guess  if  a
              window   has   scrolled   its  contents  (either  vertically  or
              horizontally).  This requires the RECORD X extension to  "snoop"
              on   X   applications   (currently  for  certain  XCopyArea  and
              XConfigureWindow  X  protocol  requests).    Examples:   Hitting
              <Return> in a terminal window when the cursor was at the bottom,
              the text scrolls up one line.  Hitting <Down>  arrow  in  a  web
              browser  window,  the  web  page  scrolls up a small amount.  Or
              scrolling with a scrollbar or mouse wheel.

              Shorter aliases:  -scr [mode]  and -noscr

              This scheme will not always detect scrolls,  but  when  it  does
              there  is  a  nice  speedup from using the VNC CopyRect encoding
              (see -wirecopyrect).  The speedup is  both  in  reduced  network
              traffic and reduced X framebuffer polling/copying.  On the other
              hand, it may induce undesired transients (e.g. a terminal cursor
              being  scrolled  up  when  it  should  not be) or other painting
              errors  (window   tearing,   bunching-up,   etc).    These   are
              automatically  repaired  in  a short period of time.  If this is
              unacceptable disable the feature with -noscrollcopyrect.

              Screen clearing kludges:  for testing at least, there  are  some
              "magic  key  sequences"  (must be done in less than 1 second) to
              aid repairing painting errors that may be seen when  using  this
              mode:

              3 Alt_L's   in a row: resend whole screen, 4 Alt_L's   in a row:
              reread and resend whole screen, 3 Super_L's in a row: mark whole
              screen  for polling, 4 Super_L's in a row: reset RECORD context,
              5 Super_L's in a row: try to push a black screen

              note: Alt_L is the Left "Alt" key (a single key) Super_L is  the
              Left  "Super"  key  (Windows  flag).  Both of these are modifier
              keys, and so should not  generate  characters  when  pressed  by
              themselves.  Also, your VNC viewer may have its own refresh hot-
              key or button.

              "mode" can be "never" (same as -noscrollcopyrect) to  never  try
              the  copyrect,  "keys" means to try it in response to keystrokes
              only, "mouse" means to try it in response to mouse events  only,
              "always" means to do both. Default: "always"

              Note:  there  can be painting errors or slow response when using
              -scale so  you  may  want  to  disable  CopyRect  in  this  case
              "-scrollcopyrect  never"  on  the  command  line  or  by remote-
              control.  Or you  can  also  use  the  "-scale  xxx:nocr"  scale
              option.

       -scr_area n

              Set  the minimum area in pixels for a rectangle to be considered
              for the -scrollcopyrect detection  scheme.   This  is  to  avoid
              wasting  the  effort  on  small rectangles that would be quickly
              updated the  normal  way.   E.g.  suppose  an  app  updated  the
              position  of  its  skinny  scrollbar  first and then shifted the
              large panel it controlled.  We want to be sure to skip the small
              scrollbar and get the large panel. Default: 60000

       -scr_skip list

              Skip  scroll  detection  for  applications  matching  the  comma
              separated list of strings in list.  Some applications  implement
              their  scrolling  in strange ways where the XCopyArea, etc, also
              applies to invisible portions of  the  window:  if  we  CopyRect
              those  areas  it  looks awful during the scroll and there may be
              painting errors left after the scroll.  Soffice.bin is the worst
              known offender.

              Use  "##"  to  denote  the  start of the application class (e.g.
              "##XTerm") and "++" to  denote  the  start  of  the  application
              instance name (e.g. "++xterm").  The string your list is matched
              against is of the form "^^WM_NAME##Class++Instance<same-for-any-
              subwindows>"  The  "xlsclients  -la"  command  will provide this
              info.

              If a  pattern  is  prefixed  with  "KEY:"  it  only  applies  to
              Keystroke  generated scrolls (e.g. Up arrow).  If it is prefixed
              with "MOUSE:" it only applies to  Mouse  induced  scrolls  (e.g.
              dragging         on        a        scrollbar).         Default:
              ##Soffice.bin,##StarOffice,##OpenOffice

       -scr_inc list

              Opposite of -scr_skip: this list is consulted first and if there
              is  a  match the window will be monitored via RECORD for scrolls
              irrespective of -scr_skip.  Use -scr_skip '*' to  skip  anything
              that  does not match your -scr_inc.  Use -scr_inc '*' to include
              everything.

       -scr_keys list

              For keystroke scroll detection, only apply the RECORD heuristics
              to  the  comma  separated list of keysyms in list.  You may find
              the RECORD overhead for every one of  your  keystrokes  disrupts
              typing  too  much,  but you don't want to turn it off completely
              with "-scr mouse"  and  -scr_parms  does  not  work  or  is  too
              confusing.

              The  listed  keysyms  can  be numeric or the keysym names in the
              <X11/keysymdef.h>  header  file  or  from  the  xev(1)  program.
              Example: "-scr_keys Up,Down,Return".  One probably wants to have
              application specific lists (e.g. for terminals, etc) but that is
              too icky to think about for now...

              If  list  begins  with the "-" character the list is taken as an
              exclude list: all keysyms except those list will be  considered.
              The  special  string  "builtin"  expands  to an internal list of
              keysyms that are likely  to  cause  scrolls.   BTW,  by  default
              modifier  keys,  Shift_L, Control_R, etc, are skipped since they
              almost never induce scrolling by themselves.

       -scr_term list

              Yet another cosmetic kludge.  Apply shell/terminal heuristics to
              applications   matching   comma  separated  list  (same  as  for
              -scr_skip/-scr_inc).  For example an  annoying  transient  under
              scroll  detection  is  if you hit Enter in a terminal shell with
              full text window, the solid text cursor block will  be  scrolled
              up.   So  for a short time there are two (or more) block cursors
              on the screen.  There are similar  scenarios,  (e.g.  an  output
              line is duplicated).

              These  transients  are  induced  by  the approximation of scroll
              detection (e.g. it detects the scroll, but not the fact that the
              block cursor was cleared just before the scroll).  In nearly all
              cases these transient  errors  are  repaired  when  the  true  X
              framebuffer  is  consulted  by the normal polling.  But they are
              distracting, so what this option  provides  is  extra  "padding"
              near  the  bottom of the terminal window: a few extra lines near
              the bottom will not be scrolled, but  rather  updated  from  the
              actual   X  framebuffer.   This  usually  reduces  the  annoying
              artifacts.  Use "none" to disable.  Default: "term"

       -scr_keyrepeat lo-hi

              If a key is held down (or otherwise repeats  rapidly)  and  this
              induces  a rapid sequence of scrolls (e.g. holding down an Arrow
              key) the "scrollcopyrect" detection and overhead may not be able
              to  keep up.  A time per single scroll estimate is performed and
              if that estimate predicts a sustainable scrollrate of  keys  per
              second  between  "lo"  and  "hi"  then  repeated  keys  will  be
              DISCARDED to maintain  the  scrollrate.  For  example  your  key
              autorepeat  may  be  25 keys/sec, but for a large window or slow
              link only 8 scrolls per second can be sustained, then roughly  2
              out  of  every  3  repeated  keys  will be discarded during this
              period. Default: "4-20"

       -scr_parms string

              Set various parameters for the scrollcopyrect mode.  The  format
              is  similar  to  that  for  -wireframe  and  packed with lots of
              parameters:

              Format:         T+B+L+R,t1+t2+t3,s1+s2+s3+s4+s5         Default:
              0+64+32+32,0.02+0.10+0.9,0.03+0.06+0.5+0.1+5.0

              If  you  leave nothing between commas: ",," the default value is
              used.   If  you  don't  specify  enough  commas,  the   trailing
              parameters are set to their defaults.

              "T+B+L+R"  indicates  four  integers for how close in pixels the
              pointer has to be from the Top, Bottom, Left, or Right edges  of
              the  window  to consider scrollcopyrect.  If -wireframe overlaps
              it takes precedence.  This is a speedup  to  quickly  exclude  a
              window  from  being  watched for scrollcopyrect: set them all to
              zero to not try the speedup (things  like  selecting  text  will
              likely be slower).

              "t1+t2+t3"  specify  three  floating point times in seconds that
              apply to scrollcopyrect detection with *Keystroke* input: t1  is
              how long to wait after a key is pressed for the first scroll, t2
              is how long to keep looking after a Keystroke  scroll  for  more
              scrolls.   t3  is  how  frequently  to try to update surrounding
              scrollbars outside of the scrolling area (0.0 to disable)

              "s1+s2+s3+s4+s5" specify five floating point  times  in  seconds
              that apply to scrollcopyrect detection with *Mouse* input: s1 is
              how long to wait after a mouse button is pressed for  the  first
              scroll,  s2  is  how long to keep waiting for additional scrolls
              after the first Mouse scroll was detected.  s3 is how frequently
              to try to update surrounding scrollbars outside of the scrolling
              area (0.0 to disable).  s4 is how long to buffer pointer  motion
              (to  try  to get fewer, bigger mouse scrolls). s5 is the maximum
              time to spend just updating the scroll window  without  updating
              the rest of the screen.

       -fixscreen string

              Periodically  "repair"  the  screen based on settings in string.
              Hopefully you won't need this option, it is intended  for  cases
              when  the  -scrollcopyrect  or  -wirecopyrect features leave too
              many painting errors, but it can be used for any scenario.  This
              option   periodically   performs   costly   operations   and  so
              interactive response may be reduced when it is on.  You can  use
              3 Alt_L's (the Left "Alt" key) taps in a row (as described under
              -scrollcopyrect) instead to manually request  a  screen  repaint
              when it is needed.

              string  is  a  comma  separated  list  of  one  or  more  of the
              following: "V=t", "C=t", "X=t", and "8=t".  In these "t"  stands
              for  a  time  in seconds (it is a floating point even though one
              should usually use values > 2 to avoid  wasting  resources).   V
              sets  how frequently the entire screen should be sent to viewers
              (it is like the 3 Alt_L's).  C sets how long  to  wait  after  a
              CopyRect  to  repaint the full screen.  X sets how frequently to
              reread the full X11 framebuffer from the X server  and  push  it
              out  to  connected  viewers.   Use  of  X should be rare, please
              report a bug if you find you need it. 8= applies only for -8to24
              mode:  it  sets  how often the non-default visual regions of the
              screen (e.g. 8bpp windows) are refreshed.  Examples:  -fixscreen
              V=10 -fixscreen C=10

       -debug_scroll

              Turn  on  debugging  info  printout  for  the scroll heuristics.
              "-ds" is an alias.  Specify it multiple times for more output.

       -noxrecord

              Disable any use of the RECORD extension.  This is currently used
              by the -scrollcopyrect scheme and to monitor X server grabs.

       -grab_buster, -nograb_buster

              Some  of the use of the RECORD extension can leave a tiny window
              for XGrabServer deadlock.  This  is  only  if  the  whole-server
              grabbing  application  expects  mouse  or  keyboard input before
              releasing the grab.  It is usually a window  manager  that  does
              this.   x11vnc  takes  care  to avoid the problem, but if caught
              x11vnc will freeze.  Without -grab_buster, the only solution  is
              to go the physical display and give it some input to satisfy the
              grabbing app.  Or manually kill and restart the  window  manager
              if  that  is  feasible.   With  -grab_buster, x11vnc will fork a
              helper thread and if x11vnc appears to be stuck in a grab  after
              a  period  of  time  (20-30  sec)  then it will inject some user
              input: button clicks, Escape, mouse motion, etc to try to  break
              the  grab.   If  you  experience  a lot of grab deadlock, please
              report a bug.

       -debug_grabs

              Turn on debugging info printout with  respect  to  XGrabServer()
              deadlock for -scrollcopyrect__mode_.

       -debug_sel

              Turn  on  debugging  info  printout  with  respect  to  PRIMARY,
              CLIPBOARD, and CUTBUFFER0 selections.

       -pointer_mode n

              Various pointer motion update schemes. "-pm" is an  alias.   The
              problem is pointer motion can cause rapid changes on the screen:
              consider the rapid changes when you drag a large  window  around
              opaquely.   Neither  x11vnc's screen polling and vnc compression
              routines nor the bandwidth to the vncviewers can keep  up  these
              rapid  screen changes: everything will bog down when dragging or
              scrolling.  So a scheme has to be used to  "eat"  much  of  that
              pointer  input  before  re-polling  the  screen  and sending out
              framebuffer updates. The mode number n can be 0 to 4 and selects
              one of the schemes desribed below.

              Note  that the -wireframe and -scrollcopyrect__mode_s complement
              -pointer_mode by detecting (and improving)  certain  periods  of
              "rapid screen change".

              n=0:  does  the  same  as  -nodragging.  (all  screen polling is
              suspended if a mouse button is pressed.)

              n=1: was  the  original  scheme  used  to  about  Jan  2004:  it
              basically  just  skips  -input_skip  keyboard  or pointer events
              before repolling the screen.

              n=2 is an improved scheme: by watching the current rate of input
              events  it  tries to detect if it should try to "eat" additional
              pointer events before continuing.

              n=3 is basically a dynamic -nodragging mode: it detects when the
              mouse motion has paused and then refreshes the display.

              n=4  attempts  to  measures network rates and latency, the video
              card read rate, and how many tiles  have  been  changed  on  the
              screen.   From  this,  it  aggressively  tries  to  push  screen
              "frames" when it decides it has enough resources to do so.   NOT
              FINISHED.

              The  default  n  is  2.  Note  that  modes  2,  3,  4  will skip
              -input_skip keyboard events  (but  it  will  not  count  pointer
              events).   Also  note  that  these  modes  are  not available in
              -threads  mode  which  has  its  own  pointer   event   handling
              mechanism.

              To  try  out  the different pointer modes to see which one gives
              the best response for your usage, it is convenient  to  use  the
              remote  control  function,  for  example "x11vnc -R pm:4" or the
              tcl/tk gui (Tuning -> pointer_mode -> n).

       -input_skip n

              For the pointer handling when non-threaded: try to read  n  user
              input  events  before  scanning  display.  n < 0 means to act as
              though there is always user input.  Default: 10

       -allinput

              Have x11vnc read and process all available client  input  before
              proceeding.

       -input_eagerly

              Similar  to  -allinput but use the handleEventsEagerly mechanism
              built into LibVNCServer.

       -speeds rd,bw,lat

              x11vnc tries to estimate some speed parameters that are used  to
              optimize   scheduling   (e.g.   -pointer_mode   4,   -wireframe,
              -scrollcopyrect) and other things.  Use the  -speeds  option  to
              set  these  manually.  The triple rd,bw,lat corresponds to video
              h/w read rate in MB/sec, network bandwidth to clients in KB/sec,
              and  network  latency  to clients in milliseconds, respectively.
              If a value is left  blank,  e.g.  "-speeds  ,100,15",  then  the
              internal scheme is used to estimate the empty value(s).

              Typical  PC  video cards have read rates of 5-10 MB/sec.  If the
              framebuffer is in main memory instead of video h/w (e.g. SunRay,
              shadowfb, dummy driver, Xvfb), the read rate may be much faster.
              "x11perf  -getimage500"  can  be  used  to  get  a  lower  bound
              (remember to factor in the bytes per pixel).  It is up to you to
              estimate the network bandwith and latency to clients.   For  the
              latency the ping(1) command can be used.

              For  convenience  there are some aliases provided, e.g. "-speeds
              modem".   The  aliases  are:  "modem"  for  6,4,200;  "dsl"  for
              6,100,50; and "lan" for 6,5000,1

       -wmdt string

              For  some  features, e.g. -wireframe and -scrollcopyrect, x11vnc
              has to  work  around  issues  for  certain  window  managers  or
              desktops (currently kde and xfce).  By default it tries to guess
              which one, but it can guess incorrectly.   Use  this  option  to
              indicate  which  wm/dt.   string  can  be "gnome", "kde", "cde",
              "xfce", or "root" (classic X wm).  Anything else is  interpreted
              as "root".

       -debug_pointer

              Print debugging output for every pointer event.

       -debug_keyboard

              Print debugging output for every keyboard event.

       Same as -dp and -dk, respectively.  Use multiple times for more output.

       -defer time

              Time  in  ms  to  delay  sending  updates  to  connected clients
              (deferUpdateTime)  Default: 20

       -wait time

              Time in ms to pause between screen polls.  Used to cut  down  on
              load.  Default: 20

       -extra_fbur n

              Perform  extra  FrameBufferUpdateRequests checks to try to be in
              better sync with the  client's  requests.   What  this  does  is
              perform  extra  polls  of  the  client  socket at critical times
              (before '-defer' and '-wait' calls.)  The default is  n=1.   Set
              to  a  larger  number  to  insert  more  checks or set to n=0 to
              disable.  A downside of these extra calls  is  that  more  mouse
              input may be processed than desired.

       -wait_ui factor

              Factor  by  which to cut the -wait time if there has been recent
              user  input  (pointer  or  keyboard).   Improves  response,  but
              increases  the load whenever you are moving the mouse or typing.
              Default: 2.00

       -setdefer n

              When the -wait_ui mechanism cuts down the wait time ms, set  the
              defer  time  to  the same ms value. n=1 to enable, 0 to disable,
              and -1 to set defer to  0  (no  delay).   Similarly,  2  and  -2
              indicate 'urgent_update' mode should be used to push the updates
              even sooner.  Default: 1

       -nowait_bog

              Do not detect if the screen polling is "bogging down" and  sleep
              more.  Some activities with no user input can slow things down a
              lot: consider a large terminal window with a long build  running
              in  it  continuously  streaming  text output.  By default x11vnc
              will try to detect this (3 screen polls in  a  row  each  longer
              than  0.25  sec with no user input), and sleep up to 1.5 secs to
              let  things  "catch  up".   Use  this  option  to  disable  that
              detection.

       -slow_fb time

              Floating point time in seconds to delay all screen polling.  For
              special purpose usage where a low frame rate is  acceptable  and
              desirable,  but  you want the user input processed at the normal
              rate so you cannot use -wait.

       -xrefresh time

              Floating point time in seconds to indicate how often to  do  the
              equivalent  of xrefresh(1) to force all windows (in the viewable
              area if -id, -sid, or -clip is used) to repaint themselves.  Use
              this only if applications misbehave by not repainting themselves
              properly.  See also -noxdamage.

       -nap, -nonap

              Monitor activity and if it  is  low  take  longer  naps  between
              screen  polls  to really cut down load when idle.  Default: take
              naps

       -sb time

              Time in seconds after NO activity (e.g. screen blank) to  really
              throttle  down the screen polls (i.e. sleep for about 1.5 secs).
              Use  0  to   disable.    Default:   60   Set   the   env.   var.
              X11VNC_SB_FACTOR to scale it.

       -readtimeout n

              Set  LibVNCServer  rfbMaxClientWait  to n seconds. On slow links
              that take a long time to paint the first screen LibVNCServer may
              hit the timeout and drop the connection.  Default: 20 seconds.

       -ping n

              Send  a  1x1  framebuffer  update to all clients every n seconds
              (e.g. to try to keep a network connection alive)

       -nofbpm, -fbpm

              If the system supports the FBPM (Frame Buffer Power  Management)
              extension  (i.e.  some  Sun systems), then prevent the video h/w
              from going into a reduced  power  state  when  VNC  clients  are
              connected.

              FBPM  capable video h/w save energy when the workstation is idle
              by going into low power states (similar to DPMS  for  monitors).
              This interferes with x11vnc's polling of the framebuffer data.

              "-nofbpm"  means  prevent  FBPM  low  power  states whenever VNC
              clients are connected, while "-fbpm" means to  not  monitor  the
              FBPM  state  at  all.   See  the  xset(1)  manpage  for details.
              -nofbpm is basically the same as running "xset  fbpm  force  on"
              periodically.  Default: -fbpm

       -nodpms, -dpms

              If  the  system  supports  the  DPMS  (Display  Power Management
              Signaling) extension, then prevent the monitor from going into a
              reduced power state when VNC clients are connected.

              DPMS  reduced  power  monitor  states  are  a good thing and you
              normally want the power down to take place (usually  x11vnc  has
              no  problem  exporting the display in this state).  You probably
              only want to use "-nodpms" to work around problems  with  Screen
              Savers  kicking  on  in  DPMS  low power states.  There is known
              problem with kdesktop_lock on KDE where the screen  saver  keeps
              kicking  in  every  time  user  input stops for a second or two.
              Specifying "-nodpms" works around it.

              "-nodpms" means prevent  DPMS  low  power  states  whenever  VNC
              clients  are  connected,  while "-dpms" means to not monitor the
              DPMS state  at  all.   See  the  xset(1)  manpage  for  details.
              -nodpms  is  basically  the same as running "xset dpms force on"
              periodically.  Default: -dpms

       -forcedpms

              If the  system  supports  the  DPMS  (Display  Power  Management
              Signaling)  extension, then try to keep the monitor in a powered
              off state.  This is to prevent  nosey  people  at  the  physical
              display from viewing what is on the screen.  Be sure to lock the
              screen before disconnecting.

              This method is far  from  bullet  proof,  e.g.  suppose  someone
              attaches  a non-DPMS monitor, or loads the machine so that there
              is a gap of time before x11vnc restores the powered  off  state?
              On  many  machines if he floods it with keyboard and mouse input
              he can see flashes of what is on the screen before the DPMS  off
              state  is  reestablished.  For this to work securely there would
              need to be support in the X server to  do  this  exactly  rather
              than approximately with DPMS.

       -clientdpms

              As -forcedpms but only when VNC clients are connected.

       -noserverdpms

              The  UltraVNC  ServerInput  extension is supported.  This allows
              the VNC viewer to click a button  that  will  cause  the  server
              (x11vnc)  to  try  to  disable  keyboard  and mouse input at the
              physical display and put the monitor in dpms powered off  state.
              Use this option to skip powering off the monitor.

       -noultraext

              Disable  the  following  UltraVNC  extensions:  SingleWindow and
              ServerInput.  The others managed by LibVNCServer (textchat,  1/n
              scaling, rfbEncodingUltra) are not.

       -chatwindow

              Place  a  local  UltraVNC  chat  window  on the X11 display that
              x11vnc is polling.  That way the person on the  VNC  viewer-side
              can  chat  with  the  person  at the physical X11 console. (e.g.
              helpdesk w/o telephone)

              For this to work the SSVNC package  (version  1.0.21  or  later)
              MUST  BE  installed  on  the  system  where  x11vnc runs and the
              'ssvnc' command must be available in $PATH.  The ssvncviewer  is
              used      as      a      chat      window      helper.       See
              http://www.karlrunge.com/x11vnc/ssvnc.html

              This option implies '-rfbversion 3.6' so as  to  trick  UltraVNC
              viewers,  otherwise  they  assume  chat  is  not  available.  To
              specify a different rfbversion, place it after  the  -chatwindow
              option on the cmdline.

              See  also  the  remote  control  'chaton' and 'chatoff' actions.
              These can also be set from the tkx11vnc GUI.

       -noxdamage

              Do not use the X DAMAGE extension to detect framebuffer  changes
              even  if  it  is  available.  Use -xdamage if your default is to
              have it off.

              x11vnc's use of the DAMAGE extension: 1)  significantly  reduces
              the  load  when  the screen is not changing much, and 2) detects
              changed areas (small ones by default) more quickly.

              Currently the DAMAGE extension is overly conservative and  often
              reports large areas (e.g. a whole terminal or browser window) as
              damaged even though the actual changed region  is  much  smaller
              (sometimes just a few pixels).  So heuristics were introduced to
              skip large areas and use the damage rectangles only  as  "hints"
              for  the  traditional  scanline  polling.   The following tuning
              parameters are introduced to adjust this behavior:

       -xd_area A

              Set the largest DAMAGE rectangle area  A  (in  pixels:  width  *
              height)  to trust as truly damaged: the rectangle will be copied
              from the framebuffer (slow) no matter  what.   Set  to  zero  to
              trust *all* rectangles. Default: 20000

       -xd_mem f

              Set  how  long  DAMAGE rectangles should be "remembered", f is a
              floating point number and is in units  of  the  scanline  repeat
              cycle  time  (32  iterations).  The default (1.0) should give no
              painting problems. Increase it if there are problems or decrease
              it to live on the edge (perhaps useful on a slow machine).

       -sigpipe string

              Broken  pipe  (SIGPIPE)  handling.   string  can  be "ignore" or
              "exit".  For "ignore" LibVNCServer will handle the  abrupt  loss
              of  a  client  and  continue, for "exit" x11vnc will cleanup and
              exit at the 1st broken connection.

              This option is not really needed since LibVNCServer is doing the
              correct thing now for quite some time.  However, for convenience
              you  can  use  it  to  ignore  other  signals,  e.g.   "-sigpipe
              ignore:HUP,INT,TERM"  in case that would be useful for some sort
              of application.  You can also put "exit:.." in the list to  have
              x11vnc  cleanup  on  the  listed signals. "-sig" is an alias for
              this  option  if  you  don't  like  the  'pipe'.  Example:  -sig
              ignore:INT,TERM,exit:USR1

       -threads, -nothreads

              Whether  or  not  to  use  the  threaded  LibVNCServer algorithm
              [rfbRunEventLoop] if libpthread is available.  In this mode  new
              threads (one for input and one for output) are created to handle
              each new client.  Default: -nothreads.

              Thread stability is much improved in version 0.9.8.

              Multiple clients in threaded mode should be stable for the  ZRLE
              encoding  on  all  platforms.   The Tight and Zlib encodings are
              currently only stable on Linux for  multiple  clients.   Compile
              with  -DTLS=__thread  if your OS and compiler and linker support
              it.

              For resizes (randr, etc.) set this env. var. to  the  number  of
              milliseconds  to  sleep:  X11VNC_THREADS_NEW_FB_SLEEP at various
              places in the  do_new_fb()  action.   This  is  to  let  various
              activities settle.  Default is about 500ms.

              Multiple clients in threaded mode could yield better performance
              for 'class-room' broadcasting usage; also in -appshare broadcast
              mode.  See also the -reflect option.

       -fs f

              If  the  fraction  of changed tiles in a poll is greater than f,
              the whole screen is updated.  Default: 0.75

       -gaps n

              Heuristic to fill in gaps in rows or cols of n  or  less  tiles.
              Used to improve text paging.  Default: 4

       -grow n

              Heuristic  to  grow  islands  of  changed  tiles  n  or wider by
              checking the tile near the boundary.  Default: 3

       -fuzz n

              Tolerance in pixels to mark a tiles edges as changed.   Default:
              2

       -debug_tiles

              Print debugging output for tiles, fb updates, etc.

       -snapfb

              Instead  of  polling the X display framebuffer (fb) for changes,
              periodically copy all of X  display  fb  into  main  memory  and
              examine  that  copy for changes.  (This setting also applies for
              non-X -rawfb modes).  Under some circumstances this will improve
              interactive response, or at least make things look smoother, but
              in others (most!) it will make the response worse.  If the video
              h/w  fb  is such that reading small tiles is very slow this mode
              could help.  To keep the "framerate" up the screen  size  x  bpp
              cannot  be  too  large.  Note that this mode is very wasteful of
              memory I/O resources  (it  makes  full  screen  copies  even  if
              nothing  changes).   It  may  be  of  use  in video capture-like
              applications, webcams, or where window tearing is a problem.

       -rawfb string

              Instead of polling  X,  poll  the  memory  object  specified  in
              string.

              For   file   polling,   to   memory  map  mmap(2)  a  file  use:
              "map:/path/to/a/file@WxHxB", with framebuffer Width, Height, and
              Bits per pixel.  "mmap:..." is the same.

              If  there  is  trouble  with  mmap,  use "file:/..."  for slower
              lseek(2) based reading.

              Use "snap:..." to imply -snapfb  mode  and  the  "file:"  access
              (this  is for unseekable devices that only provide the fb all at
              once, e.g. a video camera provides the whole frame).

              For shared memory segments string is of the form:  "shm:N@WxHxB"
              which specifies a shmid N and with WxHxB as above.  See shmat(1)
              and ipcs(1)

              If you do not supply a type "map" is assumed if the file  exists
              (see the next paragraphs for some exceptions to this.)

              If  string is "setup:cmd", then the command "cmd" is run and the
              first line from it is read and  used  as  string.   This  allows
              initializing the device, determining WxHxB, etc. These are often
              done as root so take care.

              If  the  string  begins  with  "video",  see   the   VIDEO4LINUX
              discussion  below  where  the  device  may  be  queried for (and
              possibly set) the framebuffer parameters.

              If the string begins with "console", "/dev/fb", "fb",  or  "vt",
              see  the  LINUX  CONSOLE  discussion below where the framebuffer
              device is opened and keystrokes (and possibly mouse events)  are
              inserted into the console.

              If  the  string  begins  with "vnc", see the VNC HOST discussion
              below where the framebuffer is taken as that of  another  remote
              VNC server.

              Optional  suffixes  are ":R/G/B" and "+O" to specify red, green,
              and blue masks (in hex) and an offset into  the  memory  object.
              If  the  masks are not provided x11vnc guesses them based on the
              bpp (if the colors look wrong, you need to provide the masks.)

              Another optional suffix is the Bytes  Per  Line  which  in  some
              cases   is   not   WxB/8.    Specify   it   as   WxHxB-BPL  e.g.
              800x600x16-2048.  This could be a normal width 1024 at 16bpp fb,
              but only width 800 shows up.

              So the full format is: mode:file@WxHxB:R/G/B+O-BPL

              Examples:

              -rawfb shm:210337933@800x600x32:ff/ff00/ff0000

              -rawfb map:/dev/fb0@1024x768x32

              -rawfb map:/tmp/Xvfb_screen0@640x480x8+3232

              -rawfb file:/tmp/my.pnm@250x200x24+37

              -rawfb             file:/dev/urandom@128x128x8            -rawfb
              snap:/dev/video0@320x240x24 -24to32 -rawfb video0  -rawfb  video
              -pipeinput VID -rawfb console -rawfb vt2 -rawfb vnc:somehost:0

              (see ipcs(1) and fbset(1) for the first two examples)

              In  general  all  user  input  is  discarded by default (see the
              -pipeinput option for how to use a helper  program  to  insert).
              Most  of  the  X11 (screen, keyboard, mouse) options do not make
              sense and many will cause this mode to crash,  so  please  think
              twice before setting or changing them in a running x11vnc.

              If  you DO NOT want x11vnc to close the X DISPLAY in rawfb mode,
              prepend a "+" e.g. +file:/dev/fb0...  Keeping the  display  open
              enables  the  default  remote-control  channel,  which  could be
              useful.  Alternatively, if you  specify  -noviewonly,  then  the
              mouse  and  keyboard input are STILL sent to the X display, this
              usage should be very rare, i.e.  doing  something  strange  with
              /dev/fb0.

              If the device is not "seekable" (e.g. webcam) try reading it all
              at once in full snaps via the "snap:"  mode  (note:  this  is  a
              resource  hog).   If  you are using file: or map: AND the device
              needs to be  reopened  for  *every*  snapfb  snapshot,  set  the
              environment variable: SNAPFB_RAWFB_RESET=1 as well.

              If  you  want  x11vnc  to dynamically transform a 24bpp rawfb to
              32bpp (note that this will be slower) also  supply  the  -24to32
              option.   This  would  be  useful  for, say, a video camera that
              delivers the pixel data  as  24bpp  packed  RGB.   This  is  the
              default under "video" mode if the bpp is 24.

              Normally  the bits per pixel, B, is 8, 16, or 32 (or rarely 24),
              however there is also some support for B < 8 (e.g. old  graphics
              displays  4  bpp  or  1  bpp).   In this case you certainly must
              supply the masks as  well:  WxHxB:R/G/B.   The  pixels  will  be
              padded  out  to  8  bpp  using  depth  8  truecolor.  The scheme
              currently does not work with snap fb (ask  if  interested.)  B=1
              monochrome example: file:/dev/urandom@128x128x1:1/1/1 Some other
              like this are 128x128x2:3/3/3 128x128x4:7/7/7

              For B < 8 framebuffers you can also set the env. var RAWFB_CGA=1
              to  try a CGA mapping for B=4 (e.g. linux vga16fb driver.)  Note
              with low bpp and/or resolution VGA and VGA16 modes on the  Linux
              console  one's  attempt  to  export them via x11vnc can often be
              thwarted due to special color palettes, pixel packings, and even
              video  painting  buffering.   OTOH, often experimenting with the
              RGB masks can yield something recognizable.

              VIDEO4LINUX: on Linux some  attempt  is  made  to  handle  video
              devices  (webcams  or TV tuners) automatically.  The idea is the
              WxHxB will be extracted from the device itself.  So  if  you  do
              not  supply  "@WxHxB...  parameters x11vnc will try to determine
              them.  It first tries the v4l  API  if  that  support  has  been
              compiled  in.   Otherwise  it will run the v4l- info(1) external
              program if it is available.

              The simplest examples are "-rawfb  video"  and  "-rawfb  video1"
              which   imply   the  device  file  /dev/video  and  /dev/video1,
              respectively.  You can also supply the /dev if  you  like,  e.g.
              "-rawfb /dev/video0"

              Since  the  video  capture  device  framebuffer  usually changes
              continuously (e.g. brightness fluctuations), you may want to use
              the  -wait, -slow_fb, or -defer options to lower the "framerate"
              to cut down on network VNC traffic.

              A more sophisticated video device scheme allows initializing the
              device's settings using:

              -rawfb video:<settings>

              The  prefix  could  also be, as above, e.g. "video1:" to specify
              the device file.  The v4l API must  be  available  for  this  to
              work.   Otherwise, you will need to try to initialize the device
              with an external program, e.g. xawtv, spcaview,  and  hope  they
              persist when x11vnc re-opens the device.

              <settings>  is  a  comma separated list of key=value pairs.  The
              device's brightness, color, contrast, and  hue  can  be  set  to
              percentages, e.g. br=80,co=50,cn=44,hu=60.

              The  device  filename  can  be set too if needed (if it does not
              start with "video"), e.g. fn=/dev/qcam.

              The width, height and bpp of the framebuffer  can  be  set  via,
              e.g., w=160,h=120,bpp=16.

              Related  to  the  bpp above, the pixel format can be set via the
              fmt=XXX, where XXX can be one of: GREY, HI240,  RGB555,  RGB565,
              RGB24,   and   RGB32  (with  bpp  8,  8,  16,  16,  24,  and  32
              respectively).  See http://www.linuxtv.org for  more  info  (V4L
              api).

              For  TV/rf  tuner  cards one can set the tuning mode via tun=XXX
              where XXX can be one of PAL, NTSC, SECAM, or AUTO.

              One can switch the input channel by the inp=XXX  setting,  where
              XXX is the name of the input channel (Television, Composite1, S-
              Video, etc).  Use the name that is in the information about  the
              device that is printed at startup.

              For  input channels with tuners (e.g. Television) one can change
              which station is selected by the sta=XXX setting.   XXX  is  the
              station  number.   Currently  only  the ntsc-cable-us (US cable)
              channels are built into x11vnc.  See the -freqtab  option  below
              to supply one from xawtv. If XXX is greater than 500, then it is
              interpreted as a raw frequency in KHz.

              Example:

              -rawfb video:br=80,w=320,h=240,fmt=RGB32,tun=NTSC,sta=47

              one might need to add inp=Television too for the  input  channel
              to be TV if the card doesn't come up by default in that one.

              Note  that not all video capture devices will support all of the
              above settings.

              See the -pipeinput VID option below for a  way  to  control  the
              settings  through the VNC Viewer via keystrokes.  As a shortcut,
              if  the  string  begins  "Video.."  instead  of  "video.."  then
              -pipeinput VID is implied.

              As  above,  if  you  specify  a "@WxHxB..." after the <settings>
              string they are used verbatim: the device is not queried for the
              current values.  Otherwise the device will be queried.

              LINUX  CONSOLE:   The  following describes some ways to view and
              possibly interact with the Linux text/graphics console (i.e. not
              X11 XFree86/Xorg)

              Note: If the LibVNCServer LinuxVNC program is on your system you
              may want to use that instead of the following method because  it
              will  be faster and more accurate for the Linux text console and
              includes mouse support.  There is, however, the  basic  LinuxVNC
              functionality  in  x11vnc  if you replace "console" with "vt" in
              the examples below.

              If the rawfb string begins with "console" the framebuffer device
              /dev/fb0  is  opened and /dev/tty0 is opened too.  The latter is
              used to inject keystrokes (not all are supported, but the  basic
              ones  are).   You will need to be root to inject keystrokes, but
              not necessarily to  open  /dev/fb0.   /dev/tty0  refers  to  the
              active VT, to indicate one explicitly, use, e.g., "console2" for
              /dev/tty2, etc. by indicating the specific VT number.

              For the Linux framebuffer device, /dev/fb0,  (fb1,  etc)  to  be
              enabled  the  appropriate  kernel  drivers must be loaded.  E.g.
              vesafb or  vga16fb  and  also  by  setting  the  boot  parameter
              vga=0x301  (or  0x314,  0x317, etc.)  (The vga=... method is the
              preferred way; set your machines up that way.)  Otherwise  there
              will  be  a  ´No  such device' error.  You can also load a Linux
              framebuffer driver specific to your make of video card for  more
              functionality.   Once  the  machine  is  booted  one  can  often
              'modprobe' the fb driver as root to obtain a framebuffer device.

              If you cannot get /dev/fb0  working  on  Linux,  try  using  the
              LinuxVNC  emulation  mode  by "-rawfb vtN" where N = 1, ... 6 is
              the Linux Virtual Terminal (aka virtual  console)  you  wish  to
              view,  e.g.  "-rawfb  vt2".  Unlike /dev/fb mode, it need not be
              the active Virtual Terminal.  Note that this mode can only  show
              text and not graphics.  x11vnc polls the text in /dev/vcsaN

              Set the env. var. RAWFB_VCSA_BW=1 to disable colors in the "vtN"
              mode (i.e. black and white only.)  If  you  do  not  prefer  the
              default  16bpp  set  RAWFB_VCSA_BPP  to 8 or 32.  If you need to
              tweak the rawfb parameters by using the  'console_guess'  string
              printed at startup, be sure to indicate the snap: method.

              uinput:  If the Linux version appears to be 2.6 or later and the
              "uinput" module appears to be present  (modprobe  uinput),  then
              the  uinput  method  will  be used instead of /dev/ttyN.  uinput
              allows insertion of BOTH keystrokes and mouse input  and  so  it
              preferred  when  accessing  graphical  (e.g.  QT-embedded) linux
              console  apps.   It  also  provides  more   accurate   keystroke
              insertion.   See -pipeinput UINPUT below for more information on
              this mode; you will have to use -pipeinput if you want to  tweak
              any  UINPUT  parameters.   You  may  also  want  to also use the
              -nodragging and -cursor none options.  Use "console0",  etc   or
              -pipeinput CONSOLE to force the /dev/ttyN method.

              Note  you  can  change  the  Linux VT remotely using the chvt(1)
              command to make the one you want be the active one  (e.g.  'chvt
              3').    Sometimes   switching   out   and   back   corrects  the
              framebuffer's graphics state.  For the "-rawfb vtN"  mode  there
              is no need to switch the VT's.

              To skip input injecting entirely use "consolex" or "vtx".

              The   string  "/dev/fb0"  (1,  etc.)  can  be  used  instead  of
              "console".  This can be used to specify a different  framebuffer
              device,  e.g.  /dev/fb1.   As  a  shortcut  the  "/dev/"  can be
              dropped.   If   the   name   is   something   nonstandard,   use
              "console:/dev/foofb"

              If  you  do not want x11vnc to guess the framebuffer's WxHxB and
              masks  automatically  (sometimes  the  kernel  gives   incorrect
              information),  specify  them  with a @WxHxB (and optional :R/G/B
              masks) at the end of the string.

              Examples: -rawfb console -rawfb /dev/fb0           (same) -rawfb
              console3              (force    /dev/tty3)    -rawfb    consolex
              (no  keystrokes  or  mouse)  -rawfb  console:/dev/nonstd  -rawfb
              console      -pipeinput      UINPUT:accel=4.0     -rawfb     vt3
              (/dev/tty3 w/o /dev/fb0)

              VNC HOST: if the -rawfb string is of the form "vnc:host:N"  then
              the VNC display "N" on the remote VNC server "host" is connected
              to  (i.e.  x11vnc  acts  as  a  VNC  client  itself)  and   that
              framebuffer  is  exported.   This  is  the  same  as  the option
              "-reflect host:N".

              This mode is really only of use if you  are  trying  to  improve
              performance  in  the  case  of  many (e.g. >10) simultaneous VNC
              viewers, and you try a  divide  and  conquer  scheme  to  reduce
              bandwidth  and  improve  responsiveness.   However, another user
              found this mode useful to export a demo display through  a  slow
              link:  then  multiple  demo  viewers connected to the reflecting
              x11vnc on the fast side of the link, and so avoided all  of  the
              demo  viewers  going  through  the  slow link.  Other users have
              found this mode useful to be able to take advantage of  some  of
              x11vnc's  many  features that other VNC servers do not have, for
              example  SSL  encryption,  single  port  http  and  https,  unix
              usernames  and  passwords,  and  -allow,  -zeroconf,  -clip, and
              -scale options and others.

              For the  classroom  broadcast  example,  if  there  will  be  64
              simultaneous VNC viewers this can lead to a lot of redundant VNC
              traffic to and from the server host:N, extra CPU usage, and  all
              viewers  response can be reduced by having to wait for writes to
              the slowest  client  to  finish.   However,  if  you  set  up  8
              reflectors/repeaters started with option -rawfb vnc:host:N, then
              there are only 8 connections  to  host:N.   Each  repeater  then
              handles  8  vnc  viewer  connections  thereby spreading the load
              around.  In classroom broadcast usage, try to put the  repeaters
              on  different  switches.   This  mode  is  the  same as -reflect
              host:N.  Replace "host:N" by "listen"  or  "listen:port"  for  a
              reverse   connection.    Use   "listennofork:port"  to  use  the
              LibVNCServer  non  forking  client  listen  interface  (if  your
              LibVNCServer has it), same as setting X11VNC_REFLECT_NO_FORK=1.

              Overall  performance  will  not  be  as  good as a single direct
              connection because, among other things, there is  an  additional
              level of framebuffer polling and pointer motion can still induce
              many changes per second that must be propagated.   Tip:  if  the
              remote  VNC  is  x11vnc  doing wireframing, or an X display that
              does wireframing that gives much  better  response  than  opaque
              window dragging.  Consider the -nodragging option if the problem
              is severe.

              The env. var. X11VNC_REFLECT_PASSWORD can be set to the password
              needed    to   log   into   the   vnc   host   server,   or   to
              "file:path_to_file" to indicate a file containing  the  password
              as its first line.

              To set the pixel format that x11vnc requests as a VNC CLIENT set
              the        env.        vars:        X11VNC_REFLECT_bitsPerSample
              X11VNC_REFLECT_samplesPerPixel,                              and
              X11VNC_REFLECT_bytesPerPixel; the defaults are 8, 3, 4.  2, 3, 1
              would give a low color mode.  See the function rfbGetClient() in
              libvncclient for more info.

              The  VNC  HOST  mode  implies  -shared.   Use  -noshared  as   a
              subsequent cmdline option to disable sharing.

       -freqtab file

              For  use  with  "-rawfb  video"  for TV tuner devices to specify
              station frequencies.  Instead of using the built in  ntsc-cable-
              us mapping of station number to frequency, use the data in file.
              For stations that are not numeric, e.g. SE20,  they  are  placed
              above  the highest numbered station in the order they are found.
              Example: "-freqtab /usr/X11R6/share/xawtv/europe-west.list"  You
              can make your own freqtab by copying the xawtv format.

       -pipeinput cmd

              This  option  lets  you  supply  an external command in cmd that
              x11vnc will pipe all of the user input events  to  in  a  simple
              format.   In  -pipeinput mode by default x11vnc will not process
              any of the user input events.  If you prefix cmd with "tee:"  it
              will both send them to the pipe command and process them.  For a
              description  of  the  format  run   "-pipeinput   tee:/bin/cat".
              Another  prefix  is  "reopen"  which  means to reopen pipe if it
              exits.  Separate multiple prefixes with commas.

              In combination with -rawfb one  might  be  able  to  do  amusing
              things  (e.g.  control  non-X  devices).  To facilitate this, if
              -rawfb is in effect then the value is stored in X11VNC_RAWFB_STR
              for  the pipe command to use if it wants. Do 'env | grep X11VNC'
              for more.

              Built-in pipeinput modes (no external program required):

              If cmd is "VID" and you are using the -rawfb for a video capture
              device,  then  an  internal list of keyboard mappings is used to
              set parameters of the video.  The mappings are:

              "B" and "b" adjust the brightness up  and  down.   "H"  and  "h"
              adjust  the  hue.   "C"  and "c" adjust the colour.  "N" and "n"
              adjust the contrast.  "S" and "s" adjust the size of the capture
              screen.   "I" and "i" cycle through input channels.  Up and Down
              arrows adjust the station (if a tuner)  F1,  F2,  ...,  F6  will
              switch  the  video capture pixel format to HI240, RGB565, RGB24,
              RGB32, RGB555, and GREY  respectively.   See  -rawfb  video  for
              details.

              If  cmd  is  "CONSOLE"  or "CONSOLEn" where n is a Linux console
              number, then the linux console keystroke insertion to  /dev/ttyN
              (see -rawfb console) is performed.

              If cmd begins with "UINPUT" then the Linux uinput module is used
              to insert both keystroke and mouse events to the  Linux  console
              (see  -rawfb  above).   This  usually  is  the /dev/input/uinput
              device  file  (you  may  need   to   create   it   with   "mknod
              /dev/input/uinput c 10 223" and insert the module with "modprobe
              uinput".

              The UINPUT mode currently only does US keyboards  (a  scan  code
              option may be added), and not all keysyms are supported.  But it
              is probably more accurate than the "CONSOLE" method.

              You may want to use the options -cursor none and -nodragging  in
              this mode.

              Additional    tuning    options    may    be    supplied    via:
              UINPUT:opt1,opt2,... (a comma  separated  list).  If  an  option
              begins with "/" it is taken as the uinput device file.

              Which  uinput  is injected can be controlled by an option string
              made of the  characters  "K",  "M",  and  "B"  (see  the  -input
              option),  e.g.  "KM"  allows keystroke and motion but not button
              clicks.

              A UINPUT option of the form: accel=f, or  accel=fx+fy  sets  the
              mouse  motion "acceleration".  This is used to correct raw mouse
              relative motion into  how  much  the  application  cursor  moves
              (x11vnc  has  no control over, or knowledge of how the windowing
              application interprets the raw mouse  motions).   Typically  the
              acceleration  for  an X display is 2 (see xset "m" option).  "f"
              is a floating point number, e.g. 3.0.  Use "fx+fy" if  you  need
              to supply different corrections for x and y.

              Note:  the default acceleration is 2.0 since it seems both X and
              qt-embedded often (but not always) use this value.

              Even with a correct accel setting the mouse  position  will  get
              out  of  sync (probably due to a mouse "threshold" setting where
              the acceleration doe not  apply,  set  xset(1)  ).   The  option
              reset=N  sets  the  number  of  ms (default 150) after which the
              cursor is attempted to be reset (by forcing the mouse to (0,  0)
              via  small  increments  and  then back out to (x, y) in 1 jump),
              This correction seems to be needed but can  cause  jerkiness  or
              unexpected behavior with menus, etc.  Use reset=0 to disable.

              If  you  set  the  env.  var  X11VNC_UINPUT_THRESHOLDS  then the
              thresh=n mode will be enabled.   It  is  currently  not  working
              well.   If  |dx|  <= thresh and |dy| < thresh no acceleration is
              applied.  Use "thresh=+n" |dx|  +  |dy|  <  thresh  to  be  used
              instead (X11?)

              Example: -pipeinput UINPUT:accel=4.0 -cursor none

              If  the  uinput  device has an absolute pointer (as opposed to a
              normal mouse that is a relative pointer)  you  can  specify  the
              option  "abs".   Note that a touchpad on a laptop is an absolute
              device to some degree.  This (usually) avoids all  the  problems
              with  mouse  acceleration.   If  x11vnc has trouble deducing the
              size of the device, use "abs=WxH".  Furthermore, if  the  device
              is  a  touchscreen  (assumed  to  have  an absolute pointer) use
              "touch" or "touch=WxH".  For touchscreens, when a  mouse  button
              is pressed, a pressure increase is injected, and when the button
              is released a pressure of zero is injected.

              If touch has been set, use "touch_always=1" to indicate whenever
              the  mouse  moves  with no button pressed, a touch event of zero
              pressure should be  sent  anyway.   Also  use  "btn_touch=1"  to
              indicate  a  BTN_TOUCH keystroke press or release should be sent
              instead of a  pressure  change.   Set  "dragskip=n"  to  skip  n
              dragged  mouse  touches (with pressure applied) before injecting
              one.  To indicate the pressure that should be sent when there is
              a  button  click  for  a touchscreen device, specify pressure=n,
              e.g. n=5. The default is n=1.

              If a touch screen is being used ("touch" above) and it is having
              its  input  processed  by  tslib,  you  can  specify  the  tslib
              calibration   file   via   tslib_cal=<file>.     For    example,
              tslib_cal=/etc/pointercal.   To  get  accurate  or  even  usable
              positioning this is required when tslib is in use.

              The Linux uinput mechanism can be bypassed  and  one  can  write
              input  events  DIRECTLY  to  the  devices  instead.  To do this,
              specify one or more of the  following  for  the  input  classes:
              direct_rel=<device>  direct_abs=<device>  direct_btn=<device> or
              direct_key=<device>.  The <device>  file  is  usually  something
              like  /dev/input/event1  but  you can specify any device file or
              pipe.  You must specify each one of the above  classes  even  if
              they  correspond  to  the  same device file (rel/abs and btn are
              often the same.)  Look at the  file  /proc/bus/input/devices  to
              get  an  idea what is available and the device filenames.  Note:
              The /dev/input/mouse* devices do  not  seem  to  work,  use  the
              corresponding  /dev/input/event*  file instead.  Any input class
              not directly specified as above will be handled via  the  uinput
              mechanism.   To  disable  creating  a uinput device (and thereby
              discarding unhandled input), specify "nouinput".

              Examples:

              -pipeinput UINPUT:direct_abs=/dev/input/event1

              this was used on a qtmoko Neo freerunner (armel):

              -pipeinput               UINPUT:touch,tslib_cal=/etc/pointercal,
              direct_abs=/dev/input/event1,nouinput,dragskip=4

              (where the long line has been split into two.)

              You  can set the env. var X11VNC_UINPUT_DEBUG=1 or higher to get
              debugging output for UINPUT mode.

       -macnodim

              For the native MacOSX server, disable dimming.

       -macnosleep

              For the native MacOSX server, disable display sleep.

       -macnosaver

              For the native MacOSX server, disable screensaver.

       -macnowait

              For the native MacOSX server, do not wait for the user to switch
              back to his display.

       -macwheel n

              For  the  native  MacOSX  server, set the mouse wheel speed to n
              (default 5).

       -macnoswap

              For the native MacOSX server, do not swap mouse buttons 2 and 3.

       -macnoresize

              For the native  MacOSX  server,  do  not  resize  or  reset  the
              framebuffer even if it is detected that the screen resolution or
              depth has changed.

       -maciconanim n

              For  the  native  MacOSX  server,  set  n  to  the   number   of
              milliseconds  that the window iconify/deiconify animation takes.
              In -ncache mode this value will be used to skip the animation if
              possible. (default 400)

       -macmenu

              For  the  native  MacOSX  server, in -ncache client-side caching
              mode, try to cache pull down menus  (not  perfect  because  they
              have animated fades, etc.)

       -macuskbd

              For  the  native  MacOSX  server,  use  the  original  keystroke
              insertion code based on a US keyboard.

       -macnoopengl

              For the native MacOSX server,  do  not  use  OpenGL  for  screen
              capture,  but  rather  use  the  original, deprecated raw memory
              access method: addr = CGDisplayBaseAddress().

       -macnorawfb

              For the native MacOSX server, disable  the  raw  memory  address
              screen capture method.

              MACOSX  NOTE:  There  are  some  deprecated MacOSX interfaces to
              inject keyboard and mouse  events  and  the  raw  memory  access
              method  is deprecated as well (however, OpenGL will be preferred
              if available because it is faster.)  One can force not using any
              deprecated    interfaces    at    compile    time   by   setting
              -DX11VNC_MACOSX_NO_DEPRECATED=1 in CPPFLAGS.  Or  to  turn  them
              off  one  by  one:  -DX11VNC_MACOSX_NO_DEPRECATED_LOCALEVENTS=1,
              -DX11VNC_MACOSX_NO_DEPRECATED_POSTEVENTS=1                    or
              -DX11VNC_MACOSX_NO_DEPRECATED_FRAMEBUFFER=1  At  run  time,  for
              testing and workarounds, one can disable  them  by  using:  -env
              X11VNC_MACOSX_NO_DEPRECATED=1                               -env
              X11VNC_MACOSX_NO_DEPRECATED_LOCALEVENTS=1                   -env
              X11VNC_MACOSX_NO_DEPRECATED_POSTEVENTS=1         or         -env
              X11VNC_MACOSX_NO_DEPRECATED_FRAMEBUFFER=1   Note:   When   doing
              either  of  these  for  the  mouse  input  not  everything works
              currently, e.g. double clicks  and  wireframing.   Also,  screen
              resolution  and  pixel  depth  changes will not be automatically
              detected  unless  the  deprecated  framebuffer  interfaces   are
              allowed.

              Conversely,  if  you are compiling on an older machine that does
              not have some of the newer interfaces, you may need  to  specify
              -DX11VNC_MACOSX_NO_CGEVENTCREATESCROLLWHEELEVENT
              -DX11VNC_MACOSX_NO_CGEVENTCREATEMOUSEEVENT                    or
              -DX11VNC_MACOSX_NO_CGEVENTCREATEKEYBOARDEVENT.               Use
              -DX11VNC_MACOSX_USE_GETMAINDEVICE  to  regain   the   very   old
              QuickDraw GetMainDevice() interface (rare...)

       -gui [gui-opts]

              Start up a simple tcl/tk gui based on the remote control options
              -remote/-query described below.  Requires the "wish" program  to
              be  installed  on  the machine.  "gui-opts" is not required: the
              default is to start up both the full gui and x11vnc with the gui
              showing up on the X display in the environment variable DISPLAY.

              "gui-opts"  can  be  a comma separated list of items.  Currently
              there are these types  of  items:  1)  a  gui  mode,  a  2)  gui
              "simplicity",  3)  the X display the gui should display on, 4) a
              "tray" or "icon" mode, and 5) a gui geometry.

              1) The gui mode can be "start", "conn", or "wait" "start" is the
              default  mode  above  and  is not required.  "conn" means do not
              automatically start up x11vnc, but instead just try  to  connect
              to  an existing x11vnc process.  "wait" means just start the gui
              and nothing else (you will  later  instruct  the  gui  to  start
              x11vnc or connect to an existing one.)

              2)  The  gui simplicity is off by default (a power-user gui with
              all options is presented) To start with something less  daunting
              supply  the  string  "simple" ("ez" is an alias for this).  Once
              the gui is started you can toggle between the two with "Misc  ->
              simple_gui".

              3)  Note  the  possible  confusion regarding the potentially two
              different X displays: x11vnc polls one, but you may want the gui
              to  appear on another.  For example, if you ssh in and x11vnc is
              not running yet you may want the gui to come  back  to  you  via
              your ssh redirected X display (e.g. localhost:10).

              If  you  do  not  specify a gui X display in "gui-opts" then the
              DISPLAY environment variable and -display option are  tried  (in
              that order).  Regarding the x11vnc X display the gui will try to
              communication with, it first tries -display  and  then  DISPLAY.
              For  example, "x11vnc -display :0 -gui otherhost:0", will remote
              control an x11vnc polling :0 and display the gui on  otherhost:0
              The  "tray/icon" mode below reverses this preference, preferring
              to display on the x11vnc display.

              4) When "tray" or "icon" is specified, the gui  presents  itself
              as  a  small  icon  with  behavior typical of a "system tray" or
              "dock  applet".   The  color  of  the  icon   indicates   status
              (connected   clients)  and  there  is  also  a  balloon  status.
              Clicking on the icon gives a menu from  which  properties,  etc,
              can  be  set and the full gui is available under "Advanced".  To
              be fully  functional,  the  gui  mode  should  be  "start"  (the
              default).

              Note  that  tray  or  icon  mode  will imply the -forever x11vnc
              option (if the x11vnc server is  started  along  with  the  gui)
              unless  -connect  or  -connect_or_exit  has  been specified.  So
              x11vnc (and the tray/icon gui) will wait  for  more  connections
              after the first client disconnects.  If you want only one viewer
              connection include the -once option.

              For "icon" the gui just a small standalone window.   For  "tray"
              it  will  attempt  to  embed  itself  in  the  "system  tray" if
              possible. If "=setpass" is appended then at startup the X11 user
              will   be   prompted  to  set  the  VNC  session  password.   If
              =<hexnumber> is appended that icon will attempt to embed  itself
              in  the  window  given by hexnumber.  Use =noadvanced to disable
              the full gui. (To supply more than one,  use  "+"  sign).   E.g.
              -gui tray=setpass and -gui icon=0x3600028

              Other  modes:  "full",  the  default  and need not be specified.
              "-gui none", do not show a gui, useful to override a ~/.x11vncrc
              setting, etc.

              5) When "geom=+X+Y" is specified, that geometry is passed to the
              gui toplevel.  This is the icon in icon/tray mode, or  the  full
              gui  otherwise.   You  can  also  specify width and height, i.e.
              WxH+X+Y, but it is not recommended.  In "tray" mode the geometry
              is  ignored  unless  the system tray manager does not seem to be
              running.   One  could  imagine  using   something   like   "-gui
              tray,geom=+4000+4000"  with  a  display  manager to keep the gui
              invisible until someone logs in...

              More icon tricks, "icon=minimal" gives an icon just with the VNC
              display  number.  You can also set the font with "iconfont=...".
              The      following      could       be       useful:       "-gui
              icon=minimal,iconfont=5x8,geom=24x10+0-0"

              General examples of the -gui option: "x11vnc -gui", "x11vnc -gui
              ez"  "x11vnc  -gui  localhost:10",  "x11vnc  -gui  conn,host:0",
              "x11vnc -gui tray,ez" "x11vnc -gui tray=setpass"

              If  you  do  not  intend to start x11vnc from the gui (i.e. just
              remote control an existing one), then the gui process can run on
              a  different  machine  from  the  x11vnc  server  as  long  as X
              permissions, etc. permit communication between the two.

              FONTS: On some systems the tk fonts can be too small, jagged, or
              otherwise  unreadable.   There  are 4 env vars you can set to be
              the tk font you prefer:

              X11VNC_FONT_BOLD     main   font   for   menus   and    buttons.
              X11VNC_FONT_FIXED  font for fixed width text.

              X11VNC_FONT_BOLD_SMALL   tray  icon font.  X11VNC_FONT_REG_SMALL
              tray icon menu font.

              The last two only apply for the tray icon mode.

              Here are some examples:

              -env     X11VNC_FONT_BOLD='Helvetica     -16     bold'      -env
              X11VNC_FONT_FIXED='Courier               -14'               -env
              X11VNC_FONT_REG_SMALL='Helvetica -12'

              You can put the lines like the above  (without  the  quotes)  in
              your  ~/.x11vncrc  file  to  avoid having to specify them on the
              x11vnc command line.

       -remote command

              Remotely control some  aspects  of  an  already  running  x11vnc
              server.   "-R"  and  "-r"  are aliases for "-remote".  After the
              remote control command is sent to the running server the 'x11vnc
              -remote  ...'   x11vnc  command  exits.   You  can often use the
              -query command (see below) to see if the x11vnc server processed
              your -remote command.

              The  default  communication  channel  is  that  of  X properties
              (specifically X11VNC_REMOTE), and so this command  must  be  run
              with  correct  settings  for  DISPLAY and possibly XAUTHORITY to
              connect to the X server and set  the  property.   Alternatively,
              use  the  -display  and -auth options to set them to the correct
              values.  The running server cannot use the -novncconnect  option
              because  that disables the communication channel.  See below for
              alternate channels.

              For example: 'x11vnc -remote stop' (which is the same as ´x11vnc
              -R stop') will close down the x11vnc server.  ´x11vnc -R shared'
              will enable shared connections, and ´x11vnc -R  scale:3/4'  will
              rescale the desktop.

              To  use  a  different  name  for  the X11 property (e.g. to have
              separate communication channels for  multiple  x11vnc's  on  the
              same  display) set the X11VNC_REMOTE environment variable to the
              string       you       want,       for       example:       -env
              X11VNC_REMOTE=X11VNC_REMOTE_12345 Both sides of the channel must
              use the same unique name.

              To run a bunch of commands in a  sequence  use  something  like:
              x11vnc -R 'script:firstcmd;secondcmd;...'

              Use  x11vnc -R script:file=/path/to/file to read commands from a
              file (can be multi-line and use the comment '#' character in the
              normal  way.   The  ';' separator must still be used to separate
              each command.)

              To not try to contact another x11vnc process  and  instead  just
              run the command (or query) directly, prefix the command with the
              string "DIRECT:"

              The following -remote/-R commands are supported:

              stop            terminate the server, same as "quit"  "exit"  or
              "shutdown".

              ping             see  if the x11vnc server responds.  return is:
              ans=ping:<display>

              ping:mystring   as  above,  but  use  your  own  unique  string.
              return is: ans=ping:mystring:<xdisplay>

              blacken          try  to  push  a black fb update to all clients
              (due to timings a client could miss it). Same  as  "zero",  also
              "zero:x1,y1,x2,y2" for a rectangle.

              refresh         send the entire fb to all clients.

              reset           recreate the fb, polling memory, etc.

              id:windowid     set -id window to "windowid". empty or "root" to
              go back to root window

              sid:windowid    set -sid window to "windowid"

              id_cmd:cmd       cmds:  raise,  lower,  map,   unmap,   iconify,
              move:dXdY,  resize:dWdH,  geom:WxH+X+Y.  dX  dY, dW, and dH must
              have a leading "+" or "-" e.g.: move:-30+10 resize:+20+35  also:
              wm_delete,    wm_name:string    and    icon_name:string.    Also
              id_cmd:win=N:cmd

              waitmapped      wait until subwin is mapped.

              nowaitmapped    do not wait until subwin is mapped.

              clip:WxH+X+Y    set -clip mode to "WxH+X+Y"

              flashcmap       enable  -flashcmap mode.

              noflashcmap     disable -flashcmap mode.

              shiftcmap:n     set -shiftcmap to n.

              notruecolor     enable  -notruecolor mode.

              truecolor       disable -notruecolor mode.

              overlay         enable  -overlay mode (if applicable).

              nooverlay       disable -overlay mode.

              overlay_cursor  in -overlay mode, enable cursor drawing.

              overlay_nocursor    disable    cursor    drawing.    same     as
              nooverlay_cursor.

              8to24           enable  -8to24 mode (if applicable).

              no8to24         disable -8to24 mode.

              8to24_opts:str  set the -8to24 opts to "str".

              24to32          enable  -24to32 mode (if applicable).

              no24to32        disable -24to32 mode.

              visual:vis      set -visual to "vis"

              scale:frac      set -scale to "frac"

              scale_cursor:f  set -scale_cursor to "f"

              viewonly        enable  -viewonly mode.

              noviewonly      disable -viewonly mode.

              shared          enable  -shared mode.

              noshared        disable -shared mode.

              forever         enable  -forever mode.

              noforever       disable -forever mode.

              timeout:n        reset  -timeout to n, if there are currently no
              clients, exit unless one connects in the next n secs.

              tightfilexfer   enable  filetransfer for NEW clients.

              notightfilexfer disable filetransfer for NEW clients.

              ultrafilexfer   enable  filetransfer for clients.

              noultrafilexfer disable filetransfer for clients.

              rfbversion:n.m  set -rfbversion for new clients.

              http            enable  http client connections.

              nohttp          disable http client connections.

              deny            deny any new connections, same as "lock"

              nodeny          allow new connections, same as "unlock"

              avahi           enable  avahi service advertising.

              noavahi         disable avahi service advertising.

              mdns            enable  avahi service advertising.

              nomdns          disable avahi service advertising.

              zeroconf        enable  avahi service advertising.

              nozeroconf      disable avahi service advertising.

              connect:host    do reverse connection to host, "host" may  be  a
              comma  separated  list  of  hosts  or host:ports.  See -connect.
              Passwords   required   as    with    fwd    connections.     See
              X11VNC_REVERSE_CONNECTION_NO_AUTH=1

              disconnect:host  disconnect  any  clients  from  "host"  same as
              "close:host".  Use host "all" to close all current clients.   If
              you  know  the  client  internal  hex  ID, e.g. 0x3 (returned by
              "-query clients" and RFB_CLIENT_ID) you can use that too.

              proxy:host:port set reverse connection proxy (empty to disable).

              allowonce:host  For the next connection only,  allow  connection
              from  "host".  In  -ssl  mode  two connections are allowed (i.e.
              Fetch Cert) unless X11VNC_NO_SSL_ALLOW_TWICE=1

              allow:hostlist  set -allow list to (comma separated) "hostlist".
              See -allow and -localhost.  Do not use with -allow /path/to/file
              Use "+host" to add a single host, and use "-host"  to  delete  a
              single host

              localhost       enable  -localhost mode

              nolocalhost     disable -localhost mode

              listen:str      set -listen to str, empty to disable.

              noipv6          enable  -noipv6 mode.

              ipv6            disable -noipv6 mode.

              noipv4          enable  -noipv4 mode.

              ipv4            disable -noipv4 mode.

              6               enable  -6 IPv6 listening mode.

              no6             disable -6 IPv6 listening mode.

              lookup          disable -nolookup mode.

              nolookup        enable  -nolookup mode.

              lookup          disable -nolookup mode.

              input:str       set -input to "str", empty to disable.

              grabkbd         enable  -grabkbd mode.

              nograbkbd       disable -grabkbd mode.

              grabptr         enable  -grabptr mode.

              nograbptr       disable -grabptr mode.

              grabalways      enable  -grabalways mode.

              nograbalways    disable -grabalways mode.

              grablocal:n     set -grablocal to n.

              client_input:str  set  the K, M, B -input on a per-client basis.
              select which client as for disconnect, e.g. client_input:host:MB
              or client_input:0x2:K

              accept:cmd      set -accept "cmd" (empty to disable).

              afteraccept:cmd set -afteraccept (empty to disable).

              gone:cmd        set -gone "cmd" (empty to disable).

              noshm           enable  -noshm mode.

              shm             disable -noshm mode (i.e. use shm).

              flipbyteorder    enable -flipbyteorder mode, you may need to set
              noshm for this to do something.

              noflipbyteorder disable -flipbyteorder mode.

              onetile         enable  -onetile mode. (you may need to set  shm
              for this to do something)

              noonetile       disable -onetile mode.

              solid           enable  -solid mode

              nosolid         disable -solid mode.

              solid_color:color set -solid color (and apply it).

              blackout:str     set  -blackout  "str"  (empty to disable).  See
              -blackout for the form of "str"  (basically:  WxH+X+Y,...)   Use
              "+WxH+X+Y" to append a single rectangle use "-WxH+X+Y" to delete
              one

              xinerama        enable  -xinerama mode. (if applicable)

              noxinerama      disable -xinerama mode.

              xtrap           enable  -xtrap input mode(if applicable)

              noxtrap         disable -xtrap input mode.

              xrandr          enable  -xrandr mode. (if applicable)

              noxrandr        disable -xrandr mode.

              xrandr_mode:mode set the -xrandr mode to "mode".

              rotate:mode     set the -rotate mode to "mode".

              padgeom:WxH     set -padgeom to WxH (empty to disable) If WxH is
              "force" or "do" the padded geometry fb is immediately applied.

              quiet           enable  -quiet mode.

              noquiet         disable -quiet mode.

              modtweak        enable  -modtweak mode.

              nomodtweak      enable  -nomodtweak mode.

              xkb             enable  -xkb modtweak mode.

              noxkb           disable -xkb modtweak mode.

              capslock        enable  -capslock mode.

              nocapslock      disable -capslock mode.

              skip_lockkeys   enable  -skip_lockkeys mode.

              noskip_lockkeys disable -skip_lockkeys mode.

              skip_keycodes:str enable -xkb -skip_keycodes "str".

              sloppy_keys     enable  -sloppy_keys mode.

              nosloppy_keys   disable -sloppy_keys mode.

              skip_dups       enable  -skip_dups mode.

              noskip_dups     disable -skip_dups mode.

              add_keysyms     enable -add_keysyms mode.

              noadd_keysyms    stop  adding keysyms. those added will still be
              removed at exit.

              clear_mods      enable  -clear_mods mode and clear them.

              noclear_mods    disable -clear_mods mode.

              clear_keys      enable  -clear_keys mode and clear them.

              noclear_keys    disable -clear_keys mode.

              clear_locks     do the clear_locks action.

              clear_all       do the clear_all action.

              keystate        have x11vnc print current keystate.

              remap:str       set -remap "str" (empty to disable).  See -remap
              for  the form of "str" (basically: key1-key2,key3-key4,...)  Use
              "+key1-key2" to append a single keymapping, use "-key1-key2"  to
              delete.

              norepeat        enable  -norepeat mode.

              repeat          disable -norepeat mode.

              nofb            enable  -nofb mode.

              fb              disable -nofb mode.

              bell            enable  bell (if supported).

              nobell          disable bell.

              sendbell        ring the bell now.

              nosel           enable  -nosel mode.

              sel             disable -nosel mode.

              noprimary       enable  -noprimary mode.

              primary         disable -noprimary mode.

              nosetprimary    enable  -nosetprimary mode.

              setprimary      disable -nosetprimary mode.

              noclipboard     enable  -noclipboard mode.

              clipboard       disable -noclipboard mode.

              nosetclipboard  enable  -nosetclipboard mode.

              setclipboard    disable -nosetclipboard mode.

              seldir:str      set -seldir to "str"

              resend_cutbuffer resend the most recent CUTBUFFER0 copy

              resend_clipboard resend the most recent CLIPBOARD copy

              resend_primary   resend the most recent PRIMARY copy

              cursor:mode     enable  -cursor "mode".

              show_cursor     enable  showing a cursor.

              noshow_cursor   disable showing a cursor. (same as "nocursor")

              cursor_drag     enable  cursor changes during drag.

              nocursor_drag   disable cursor changes during drag.

              arrow:n         set -arrow to alternate n.

              xfixes          enable  xfixes cursor shape mode.

              noxfixes        disable xfixes cursor shape mode.

              alphacut:n      set -alphacut to n.

              alphafrac:f     set -alphafrac to f.

              alpharemove     enable  -alpharemove mode.

              noalpharemove   disable -alpharemove mode.

              alphablend      disable -noalphablend mode.

              noalphablend    enable  -noalphablend mode.

              cursorshape     disable -nocursorshape mode.

              nocursorshape   enable  -nocursorshape mode.

              cursorpos       disable -nocursorpos mode.

              nocursorpos     enable  -nocursorpos mode.

              xwarp           enable  -xwarppointer mode.

              noxwarp         disable -xwarppointer mode.

              always_inject   enable  -always_inject mode.

              noalways_inject disable -always_inject mode.

              buttonmap:str   set -buttonmap "str", empty to disable

              dragging        disable -nodragging mode.

              nodragging      enable  -nodragging mode.

              ncache          reenable -ncache mode.

              noncache        disable  -ncache mode.

              ncache_size:n   set -ncache size to n.

              ncache_cr       enable  -ncache_cr mode.

              noncache_cr     disable -ncache_cr mode.

              ncache_no_moveraise     enable  no_moveraise mode.

              noncache_no_moveraise   disable no_moveraise mode.

              ncache_no_dtchange      enable  ncache_no_dtchange mode.

              noncache_no_dtchange    disable ncache_no_dtchange mode.

              ncache_old_wm           enable  ncache_old_wm mode.

              noncache_old_wm         disable ncache_old_wm mode.

              ncache_no_rootpixmap    enable  ncache_no_rootpixmap.

              noncache_no_rootpixmap  disable ncache_no_rootpixmap.

              ncache_reset_rootpixmap recheck the root pixmap, ncrp

              ncache_keep_anims       enable  ncache_keep_anims.

              noncache_keep_anims     disable ncache_keep_anims.

              ncache_pad:n    set -ncache_pad to n.

              wireframe       enable  -wireframe mode. same as "wf"

              nowireframe     disable -wireframe mode. same as "nowf"

              wireframe:str   enable  -wireframe mode string.

              wireframe_mode:str enable  -wireframe mode string.

              wireframelocal  enable  wireframelocal. same as "wfl"

              nowireframe     disable wireframelocal. same as "nowfl"

              wirecopyrect:str set -wirecopyrect string. same as "wcr:"

              scrollcopyrect:str set -scrollcopyrect string. same "scr"

              noscrollcopyrect disable -scrollcopyrect__mode_. "noscr"

              scr_area:n      set -scr_area to n

              scr_skip:list   set -scr_skip to "list"

              scr_inc:list    set -scr_inc to "list"

              scr_keys:list   set -scr_keys to "list"

              scr_term:list   set -scr_term to "list"

              scr_keyrepeat:str set -scr_keyrepeat to "str"

              scr_parms:str   set -scr_parms parameters.

              fixscreen:str   set -fixscreen to "str".

              noxrecord       disable all use of RECORD extension.

              xrecord         enable  use of RECORD extension.

              reset_record    reset RECORD extension (if avail.)

              pointer_mode:n  set -pointer_mode to n. same as "pm"

              input_skip:n    set -input_skip to n.

              allinput        enable  use of -allinput mode.

              noallinput      disable use of -allinput mode.

              input_eagerly   enable  use of -input_eagerly mode.

              noinput_eagerly disable use of -input_eagerly mode.

              ssltimeout:n    set -ssltimeout to n.

              speeds:str      set -speeds to str.

              wmdt:str        set -wmdt to str.

              debug_pointer   enable  -debug_pointer, same as "dp"

              nodebug_pointer disable -debug_pointer, same as "nodp"

              debug_keyboard   enable  -debug_keyboard, same as "dk"

              nodebug_keyboard disable -debug_keyboard, same as "nodk"

              keycode:n       inject keystroke 'keycode' (xmodmap -pk)

              keycode:n,down  inject 'keycode' (down=0,1)

              keysym:str      inject keystroke 'keysym' (number/name)

              keysym:str,down inject 'keysym' (down=0,1)

              ptr:x,y,mask    inject pointer event x, y, button-mask

              fakebuttonevent:button,down direct XTestFakeButtonEvent.

              sleep:t         sleep floating point time t.

              get_xprop:p     get X property named 'p'.

              set_xprop:p:val  set  X  property  named  'p'  to  'val'.   p ->
              id=NNN:p for hex/dec window id.

              wininfo:id      get info about X window id.  use 'root' for root
              window, use +id for children.

              grab_state      get state of pointer and keyboard grab.

              pointer_pos     print XQueryPointer x,y cursor position.

              pointer_x       print XQueryPointer x cursor position.

              pointer_y       print XQueryPointer y cursor position.

              pointer_same    print XQueryPointer ptr on same screen.

              pointer_root    print XQueryPointer curr ptr rootwin.

              pointer_mask    print XQueryPointer button and mods mask

              mouse_x         print x11vnc's idea of cursor position.

              mouse_y         print x11vnc's idea of cursor position.

              noop            do nothing.

              defer:n         set -defer to n ms,same as deferupdate:n

              wait:n          set -wait to n ms.

              extra_fbur:n    set -extra_fbur to n.

              wait_ui:f       set -wait_ui factor to f.

              setdefer:n      set -setdefer to -2,-1,0,1, or 2.

              wait_bog        disable -nowait_bog mode.

              nowait_bog      enable  -nowait_bog mode.

              slow_fb:f       set -slow_fb to f seconds.

              xrefresh:f      set -xrefresh to f seconds.

              readtimeout:n   set read timeout to n seconds.

              nap             enable  -nap mode.

              nonap           disable -nap mode.

              sb:n            set -sb to n s, same as screen_blank:n

              fbpm            disable -nofbpm mode.

              nofbpm          enable  -nofbpm mode.

              dpms            disable -nodpms mode.

              nodpms          enable  -nodpms mode.

              forcedpms       enable  -forcedpms mode.

              noforcedpms     disable -forcedpms mode.

              clientdpms      enable  -clientdpms mode.

              noclientdpms    disable -clientdpms mode.

              noserverdpms    enable  -noserverdpms mode.

              serverdpms      disable -noserverdpms mode.

              noultraext      enable  -noultraext mode.

              ultraext        disable -noultraext mode.

              chatwindow      enable  local chatwindow mode.

              nochatwindow    disable local chatwindow mode.

              chaton          begin chat using local window.

              chatoff         end   chat using local window.

              xdamage         enable  xdamage polling hints.

              noxdamage       disable xdamage polling hints.

              xd_area:A       set -xd_area max pixel area to "A"

              xd_mem:f        set -xd_mem remembrance to "f"

              fs:frac         set -fs fraction to "frac", e.g. 0.5

              gaps:n          set -gaps to n.

              grow:n          set -grow to n.

              fuzz:n          set -fuzz to n.

              snapfb          enable  -snapfb mode.

              nosnapfb        disable -snapfb mode.

              rawfb:str       set -rawfb mode to "str".

              uinput_accel:f  set uinput_accel to f.

              uinput_thresh:n set uinput_thresh to n.

              uinput_reset:n  set uinput_reset to n ms.

              uinput_always:n set uinput_always to 1/0.

              progressive:n     set  LibVNCServer  -progressive  slice  height
              parameter to n.

              desktop:str     set -desktop name to str for new clients.

              rfbport:n       set -rfbport to n.

              macnosaver      enable  -macnosaver mode.

              macsaver        disable -macnosaver mode.

              macnowait       enable  -macnowait  mode.

              macwait         disable -macnowait  mode.

              macwheel:n      set -macwheel to n.

              macnoswap       enable  -macnoswap mouse button mode.

              macswap         disable -macnoswap mouse button mode.

              macnoresize     enable  -macnoresize mode.

              macresize       disable -macnoresize mode.

              maciconanim:n   set -maciconanim to n.

              macmenu         enable  -macmenu  mode.

              macnomenu       disable -macmenu  mode.

              macuskbd        enable  -macuskbd mode.

              macnouskbd      disable -macuskbd mode.

              httpport:n      set -httpport to n.

              httpdir:dir     set -httpdir to dir (and enable http).

              enablehttpproxy   enable  -enablehttpproxy mode.

              noenablehttpproxy disable -enablehttpproxy mode.

              alwaysshared     enable  -alwaysshared mode.

              noalwaysshared   disable  -alwaysshared  mode.   (may  interfere
              with other options)

              nevershared      enable  -nevershared mode.

              nonevershared    disable -nevershared mode.  (may interfere with
              other options)

              dontdisconnect   enable  -dontdisconnect mode.

              nodontdisconnect disable -dontdisconnect mode.   (may  interfere
              with other options)

              debug_xevents   enable  debugging X events.

              nodebug_xevents disable debugging X events.

              debug_xdamage   enable  debugging X DAMAGE mechanism.

              nodebug_xdamage disable debugging X DAMAGE mechanism.

              debug_wireframe enable   debugging wireframe mechanism.

              nodebug_wireframe disable debugging wireframe mechanism.

              debug_scroll    enable  debugging scrollcopy mechanism.

              nodebug_scroll  disable debugging scrollcopy mechanism.

              debug_tiles     enable  -debug_tiles

              nodebug_tiles   disable -debug_tiles

              debug_grabs     enable  -debug_grabs

              nodebug_grabs   disable -debug_grabs

              debug_sel       enable  -debug_sel

              nodebug_sel     disable -debug_sel

              debug_ncache    enable  -debug_ncache

              nodebug_ncache  disable -debug_ncache

              dbg             enable  -dbg crash shell

              nodbg           disable -dbg crash shell

              noremote         disable  the  -remote  command  processing,  it
              cannot be turned back on.

              bcx_xattach:str  This remote control command is for use with the
              BARCO  xattach  program  or  the  x2x  program.   Both  of these
              programs are for 'pointer and keyboard' sharing between separate
              X  displays.   In  general  the two displays are usually nearby,
              e.g. on the same desk, and this  allows  the  user  to  share  a
              single  pointer  and  keyboard between them.  The user moves the
              mouse to an edge and then the mouse pointer appears to 'jump' to
              the  other  display  screen.   Thus  it emulates what a single X
              server would do  for  two  screens  (e.g.  :0.0  and  :0.1)  The
              illusion  of  a single Xserver with multiple screens is achieved
              by forwarding events to the 2nd one via the XTEST extension.

              What the x11vnc bcx_xattach command  does  is  to  perform  some
              pointer  movements to try to INDUCE xattach/x2x to 'jump' to the
              other display.  In what follows the ´master' display  refers  to
              the  one  that when it has ´focus' it is basically doing nothing
              besides watching for the mouse to go over an edge.  The  'slave'
              display  refers  to  the  one to which the mouse and keyboard is
              redirected to once an edge in the master has been crossed.  Note
              that  the  x11vnc  executing the bcx_xattach command MUST be the
              one connected to the *master* display.

              Also note that when input is being redirected (via  XTEST)  from
              the  master  display  to the slave display, the master display's
              pointer and keyboard are *grabbed* by xattach/x2x.   x11vnc  can
              use  this  info  to verify that the master/slave mode change has
              taken place correctly.  If you  specify  the  "ifneeded"  option
              (see  below)  and  the initial grab state is that of the desired
              final  state,  then  no  pointer  movements  are  injected   and
              "DONE,GRAB_OK" is returned.

              "str"  must  contain  one of "up", "down", "left", or "right" to
              indicate the direction of the 'jump'.  "str" must  also  contain
              one  of  "master_to_slave"  or "slave_to_master" to indicate the
              type of mode change induced by the jump.  Use "M2S" and "S2M" as
              shorter aliases.

              "str"  may be a "+" separated list of additional tuning options.
              The "shift=n" option indicates an  offset  shift  position  away
              from  (0,0)  (default  20).   "final=x+y"  specifies  the  final
              position of the cursor at the end of the normal  move  sequence;
              default  30+30.   "extra_move=x+y"  means to do one more pointer
              move after "final" to  x+y.   "dt=n"  sets  the  sleep  time  in
              milliseconds  between  pointer  moves  (default: 40ms) "retry=n"
              specifies the maximum number of retries if the grab state change
              fails.  "ifneeded"  means  to not apply the pointer movements if
              the initial grab state is  that  of  the  desired  final  state.
              "nograbcheck"  means  to  not check if the grab state changed as
              expected and only apply the pointer  movements  (default  is  to
              check the grab states.)

              If you do not specify "up", etc., to bcx_xattach nothing will be
              attempted    and    the    command    returns     the     string
              FAIL,NO_DIRECTION_SPECIFIED.     If    you    do   not   specify
              "master_to_slave" or "M2S", etc., to bcx_xattach nothing will be
              attempted     and     the    command    returns    the    string
              FAIL,NO_MODE_CHANGE_SPECIFIED.

              Otherwise, the returned string will contain "DONE".  It will  be
              "DONE,GRAB_OK"  if  the  grab  state  changed as expected (or if
              "ifneeded" was supplied and the initial grab state  was  already
              the  desired one.)  If the initial grab state was incorrect, but
              the   final   grab   state    was    correct    then    it    is
              "DONE,GRAB_FAIL_INIT".   If  the initial grab state was correct,
              but  the  final  grab   state   was   incorrect   then   it   is
              "DONE,GRAB_FAIL_FINAL".   If  both  are  incorrect  it  will  be
              "DONE,GRAB_FAIL".   Under  grab  failure  the  string  will   be
              followed  by  ":p1,k1-p2,k2"  where  p1,k1 indicates the initial
              pointer and keyboard grab states and p2,k2 the  final  ones.  If
              GRAB_FAIL  or GRAB_FAIL_FINAL occurs, the action will be retried
              up to 3 times; trying to reset the  state  and  sleeping  a  bit
              between  each try.  Set retry=n to adjust the number of retries,
              zero to disable retries.

              Examples:  -R  bcx_xattach:down+M2S  -R  bcx_xattach:up+S2M   -R
              bcx_xattach:up+S2M+nograbcheck+dt=30                          -R
              bcx_xattach:down+M2S+extra_move=100+100

              or use -Q instead of -R to retrieve the result text.

              End of the bcx_xattach:str description.

              The vncconnect(1) command from standard  VNC  distributions  may
              also  be used if string is prefixed with "cmd=" E.g. 'vncconnect
              cmd=stop'.  Under some circumstances xprop(1)  can  used  if  it
              supports -set (see the FAQ).

              If  "-connect  /path/to/file"  has  been supplied to the running
              x11vnc server then that file can  be  used  as  a  communication
              channel  (this  is  the  only  way to remote control one of many
              x11vnc's  polling  the  same  X  display)  Simply  run:  'x11vnc
              -connect  /path/to/file  -remote ...'  or you can directly write
              to the file via something like: "echo cmd=stop > /path/to/file",
              etc.

       -query variable

              Like  -remote, except just query the value of variable.  "-Q" is
              an  alias  for  "-query".   Multiple  queries  can  be  done  by
              separating  variables  by  commas,  e.g.  -query  var1,var2. The
              results        come        back        in        the        form
              ans=var1:value1,ans=var2:value2,...  to the standard output.  If
              a variable is  read-only,  it  comes  back  with  prefix  "aro="
              instead of "ans=".

              Some -remote commands are pure actions that do not make sense as
              variables, e.g. "stop" or "disconnect", in these cases the value
              returned   is   "N/A".   To  direct  a  query  straight  to  the
              X11VNC_REMOTE property or connect file use "qry=..." instead  of
              "cmd=..."

              ans=    stop    quit   exit   shutdown   ping   resend_cutbuffer
              resend_clipboard resend_primary blacken zero refresh reset close
              disconnect  id_cmd id sid waitmapped nowaitmapped clip flashcmap
              noflashcmap shiftcmap truecolor  notruecolor  overlay  nooverlay
              overlay_cursor        overlay_yescursor       nooverlay_nocursor
              nooverlay_cursor  nooverlay_yescursor   overlay_nocursor   8to24
              no8to24  8to24_opts  24to32  no24to32  visual scale scale_cursor
              viewonly  noviewonly  shared  noshared  forever  noforever  once
              timeout      tightfilexfer     notightfilexfer     ultrafilexfer
              noultrafilexfer rfbversion deny lock nodeny  unlock  avahi  mdns
              zeroconf noavahi nomdns nozeroconf connect proxy allowonce allow
              noipv6 ipv6 noipv4  ipv4  no6  6  localhost  nolocalhost  listen
              lookup  nolookup accept afteraccept gone shm noshm flipbyteorder
              noflipbyteorder  onetile  noonetile  solid_color  solid  nosolid
              blackout  xinerama  noxinerama  xtrap  noxtrap  xrandr  noxrandr
              xrandr_mode rotate padgeom quiet q noquiet  modtweak  nomodtweak
              xkb  noxkb  capslock  nocapslock  skip_lockkeys  noskip_lockkeys
              skip_keycodes sloppy_keys  nosloppy_keys  skip_dups  noskip_dups
              add_keysyms  noadd_keysyms  clear_mods  noclear_mods  clear_keys
              noclear_keys  clear_all  clear_locks   keystate   remap   repeat
              norepeat   fb  nofb  bell  nobell  sendbell  sel  nosel  primary
              noprimary   setprimary   nosetprimary   clipboard    noclipboard
              setclipboard  nosetclipboard  seldir  cursorshape  nocursorshape
              cursorpos   nocursorpos   cursor_drag    nocursor_drag    cursor
              show_cursor noshow_cursor nocursor arrow xfixes noxfixes xdamage
              noxdamage  xd_area   xd_mem   alphacut   alphafrac   alpharemove
              noalpharemove   alphablend   noalphablend   xwarppointer   xwarp
              noxwarppointer noxwarp always_inject  noalways_inject  buttonmap
              dragging  nodragging  ncache_cr  noncache_cr ncache_no_moveraise
              noncache_no_moveraise  ncache_no_dtchange   noncache_no_dtchange
              ncache_no_rootpixmap                      noncache_no_rootpixmap
              ncache_reset_rootpixmap          ncrp          ncache_keep_anims
              noncache_keep_anims   ncache_old_wm  noncache_old_wm  ncache_pad
              ncache   noncache   ncache_size   debug_ncache    nodebug_ncache
              wireframe_mode  wireframe wf nowireframe nowf wireframelocal wfl
              nowireframelocal nowfl  wirecopyrect  wcr  nowirecopyrect  nowcr
              scr_area   scr_skip   scr_inc  scr_keys  scr_term  scr_keyrepeat
              scr_parms scrollcopyrect scr  noscrollcopyrect  noscr  fixscreen
              noxrecord   xrecord   reset_record  pointer_mode  pm  input_skip
              allinput noallinput input_eagerly noinput_eagerly input  grabkbd
              nograbkbd  grabptr  nograbptr  grabalways nograbalways grablocal
              client_input   ssltimeout   speeds   wmdt    debug_pointer    dp
              nodebug_pointer  nodp  debug_keyboard  dk  nodebug_keyboard nodk
              keycode keysym ptr  fakebuttonevent  sleep  get_xprop  set_xprop
              wininfo   bcx_xattach   deferupdate  defer  setdefer  extra_fbur
              wait_ui wait_bog nowait_bog slow_fb  xrefresh  wait  readtimeout
              nap  nonap  sb  screen_blank  fbpm nofbpm dpms nodpms clientdpms
              noclientdpms  forcedpms  noforcedpms   noserverdpms   serverdpms
              noultraext  ultraext  chatwindow  nochatwindow chaton chatoff fs
              gaps grow fuzz snapfb nosnapfb rawfb uinput_accel  uinput_thresh
              uinput_reset   uinput_always  progressive  rfbport  http  nohttp
              httpport httpdir enablehttpproxy noenablehttpproxy  alwaysshared
              noalwaysshared    nevershared    noalwaysshared   dontdisconnect
              nodontdisconnect    desktop    debug_xevents     nodebug_xevents
              debug_xevents    debug_xdamage   nodebug_xdamage   debug_xdamage
              debug_wireframe nodebug_wireframe  debug_wireframe  debug_scroll
              nodebug_scroll  debug_scroll debug_tiles dbt nodebug_tiles nodbt
              debug_tiles debug_grabs nodebug_grabs debug_sel nodebug_sel  dbg
              nodbg   macnosaver   macsaver   nomacnosaver  macnowait  macwait
              nomacnowait macwheel macnoswap macswap  nomacnoswap  macnoresize
              macresize  nomacnoresize maciconanim macmenu macnomenu nomacmenu
              macuskbd nomacuskbd noremote

              aro=  noop display vncdisplay  icon_mode  autoport  loop  loopbg
              desktopname  guess_desktop  guess_dbus http_url auth xauth users
              rootshift  clipshift  scale_str  scaled_x  scaled_y  scale_numer
              scale_denom      scale_fac_x      scale_fac_y      scaling_blend
              scaling_nomult4 scaling_pad scaling_interpolate inetd privremote
              unsafe safer nocmds passwdfile unixpw unixpw_nis unixpw_list ssl
              ssl_pem sslverify stunnel  stunnel_pem  https  httpsredir  usepw
              using_shm logfile o flag rmflag rc norc h help V version lastmod
              bg sigpipe threads readrate netrate netlatency pipeinput clients
              client_count   pid   ext_xtest   ext_xtrap  ext_xrecord  ext_xkb
              ext_xshm   ext_xinerama   ext_overlay   ext_xfixes   ext_xdamage
              ext_xrandr   rootwin  num_buttons  button_mask  mouse_x  mouse_y
              grab_state   pointer_pos   pointer_x   pointer_y    pointer_same
              pointer_root  pointer_mask  bpp  depth indexed_color dpy_x dpy_y
              wdpy_x wdpy_y off_x off_y cdpy_x cdpy_y  coff_x  coff_y  rfbauth
              passwd viewpasswd

       -QD variable

              Just  like  -query  variable,  but returns the default value for
              that parameter (no running x11vnc server is consulted)

       -sync

              By default -remote commands are run asynchronously, that is, the
              request  is posted and the program immediately exits.  Use -sync
              to have the program wait for an acknowledgement from the  x11vnc
              server  that command was processed (somehow).  On the other hand
              -query requests are always processed synchronously because  they
              have to wait for the answer.

              Also  note that if both -remote and -query requests are supplied
              on  the  command  line,   the   -remote   is   processed   first
              (synchronously:  no need for -sync), and then the -query request
              is processed in the normal way.  This allows for a reliable  way
              to  see if the -remote command was processed by querying for any
              new settings.  Note however that  there  is  timeout  of  a  few
              seconds  (see  the next paragraph) so if the x11vnc takes longer
              than that to process the requests the requester will think  that
              a failure has taken place.

              The  default  is  to  wait 3.5 seconds.  Or if cmd=stop only 1.0
              seconds.  If cmd matches 'script:' then it will wait up to  10.0
              seconds.   Set  X11VNC_SYNC_TIMEOUT to the number of seconds you
              want it to wait.

       -query_retries str

              If a query fails to get a response from an x11vnc server,  retry
              up  to  n  times.  str is specified as n[:t][/match]  Optionally
              the delay between tries may be specified by "t" a floating point
              time  (default  0.5 seconds.)  Note: the response is not checked
              for validity or whether it corresponds to the query  sent.   The
              query  "ping:mystring" may be used to help uniquely identify the
              query.  Optionally, a matching string after a "/" will  be  used
              to check the result text.  Up to n retries will take place until
              the matching string is found in the output text.  If  the  match
              string is never found the program's exit code is 1; if the match
              is found it exits with 0.  Note that there may be stdout printed
              for  each  retry  (i.e.  multiple  lines printed out to stdout.)
              Example: -query_retries 4:1.5/grab_state

       -remote_prefix str

              Enable a remote-control communication channel for connected  VNC
              clients.   str  is  a  non-empty  string.  If a VNC client sends
              rfbCutText having the prefix str  then  the  part  after  it  is
              processed  as  though it were sent via 'x11vnc -remote ...'.  If
              it begins with neither 'cmd=' nor 'qry=' then 'qry=' is assumed.
              Any corresponding output text for that remote control command is
              sent back to all client as rfbCutText.  The returned  output  is
              also prefixed with str.  Example: -remote_prefix DO_THIS:

              Note  that enabling -remote_prefix allows the remote VNC viewers
              to run x11vnc -remote commands.  Do not use this option if  they
              are not to be trusted.

       -noremote, -yesremote

              Do  not  process  any  remote  control  commands or queries.  Do
              process remote control commands or queries.  Default: -yesremote

              A note about security wrt remote control commands.   If  someone
              can   connect   to   the  X  display  and  change  the  property
              X11VNC_REMOTE, then they can remotely control x11vnc.   Normally
              access  to  the  X  display is protected.  Note that if they can
              modify  X11VNC_REMOTE  on  the  X  server,  they   have   enough
              permissions  to also run their own x11vnc and thus have complete
              control  of  the  desktop.   If  the   "-connect  /path/to/file"
              channel  is  being  used,  obviously  anyone  who  can  write to
              /path/to/file can  remotely  control  x11vnc.   So  be  sure  to
              protect  the  X  display and that file's write permissions.  See
              -privremote below.

              If you are paranoid and do not think  -noremote  is  enough,  to
              disable   the  X11VNC_REMOTE  property  channel  completely  use
              -novncconnect, or use the -safer option that shuts  many  things
              off.

       -unsafe

              A  few  remote  commands  are  disabled  by  default (currently:
              id:pick,  accept:<cmd>,   gone:<cmd>,   and   rawfb:setup:<cmd>)
              because  they are associated with running external programs.  If
              you specify -unsafe,  then  these  remote-control  commands  are
              allowed.   Note  that  you can still specify these parameters on
              the command line,  they  just  cannot  be  invoked  via  remote-
              control.

       -safer

              Equivalent  to: -novncconnect -noremote and prohibiting -gui and
              the -connect file. Shuts off communcation channels.

       -privremote

              Perform some sanity checks and disable  remote-control  commands
              if  it  appears  that  the  X  DISPLAY and/or connectfile can be
              accessed by other users.  Once  remote-control  is  disabled  it
              cannot be turned back on.

       -nocmds

              No  external  commands  (e.g.   system(3) , popen(3) , exec(3) )
              will be run at all.

       -allowedcmds list

              list contains a  comma  separated  list  of  the  only  external
              commands  that  can be run.  The full list of associated options
              is:

              stunnel, ssl, unixpw, WAIT, zeroconf, id,  accept,  afteraccept,
              gone,   pipeinput,   v4l-info,   rawfb-setup,   dt,   gui,  ssh,
              storepasswd, passwdfile, custom_passwd, findauth, crash.

              See each option's help to learn the associated external command.
              Note  that  the -nocmds option takes precedence and disables all
              external commands.

       -deny_all

              For use with -remote nodeny:  start  out  denying  all  incoming
              clients until "-remote nodeny" is used to let them in.

       These options are passed to LibVNCServer:

       -rfbport port

              TCP port for RFB protocol

       -rfbwait time

              max time in ms to wait for RFB client

       -rfbauth passwd-file

              use  authentication  on  RFB  protocol (use 'x11vnc -storepasswd
              pass file' to create a password file)

       -rfbversion 3.x

              Set the version of the RFB we choose to advertise

       -permitfiletransfer

              permit file transfer support

       -passwd plain-password

              use authentication (use plain-password as password, USE AT  YOUR
              RISK)

       -deferupdate time

              time in ms to defer updates (default 40)

       -deferptrupdate time

              time in ms to defer pointer updates (default none)

       -desktop name

              VNC desktop name (default "LibVNCServer")

       -alwaysshared

              always treat new clients as shared

       -nevershared

              never treat new clients as shared

       -dontdisconnect

              don't   disconnect   existing  clients  when  a  new  non-shared
              connection comes in (refuse new connection instead)

       -httpdir dir-path

              enable http server using dir-path home

       -httpport portnum

              use portnum for http connection

       -enablehttpproxy

              enable http proxy support

       -progressive height

              enable progressive updating for slow links

       -listen ipaddr

              listen for connections  only  on  network  interface  with  addr
              ipaddr. '-listen localhost' and hostname work too.

       libvncserver-tight-extension options:

       -disablefiletransfer

              disable file transfer

       -ftproot string

              set ftp root

FILES

       $HOME/.x11vncrc, $HOME/.Xauthority

ENVIRONMENT

       DISPLAY, XAUTHORITY, HOME

       The  following are set for the auxiliary commands run by -accept, -gone
       and other cases:

       RFB_CLIENT_IP,   RFB_CLIENT_PORT,    RFB_SERVER_IP,    RFB_SERVER_PORT,
       RFB_X11VNC_PID,  RFB_CLIENT_ID,  RFB_CLIENT_COUNT,  RFB_MODE  RFB_STATE
       RFB_LOGIN_VIEWONLY   RFB_LOGIN_TIME    RFB_CURRENT_TIME    RFB_USERNAME
       RFB_SSL_CLIENT_CERT

SEE ALSO

       vncviewer(1),   vncpasswd(1),   vncconnect(1),  vncserver(1),  Xvnc(1),
       xev(1),  xdpyinfo(1),  xwininfo(1),  xprop(1),  xmodmap(1),  xrandr(1),
       Xserver(1),     xauth(1),    xhost(1),    Xsecurity(7),    xmessage(1),
       XGetImage(3X11), ipcrm(1), inetd(1), xdm(1),  gdm(1),  kdm(1),  ssh(1),
       stunnel(8),   su(1),  http://www.tightvnc.com,  http://www.realvnc.com,
       http://www.karlrunge.com/x11vnc/, http://www.karlrunge.com/x11vnc/#faq

AUTHORS

       x11vnc was written by Karl J. Runge <runge@karlrunge.com>, it  is  part
       of   the  LibVNCServer  project  <http://sf.net/projects/libvncserver>.
       This manual page is  based  one  the  one  written  by  Ludovic  Drolez
       <ldrolez@debian.org>,  for  the  Debian  project  (both  may be used by
       others).