Provided by: xdmx_1.11.4-0ubuntu9_i386 bug


       Xdmx - Distributed Multi-head X server


       Xdmx [:display] [option ...]


       Xdmx  is  a proxy X server that uses one or more other X servers as its
       display devices.  It provides multi-head X functionality  for  displays
       that  might  be  located  on  different  machines.  Xdmx functions as a
       front-end X server that acts as a proxy to a set of back-end X servers.
       All  of  the  visible  rendering  is  passed to the back-end X servers.
       Clients connect to the Xdmx front-end, and  everything  appears  as  it
       would  in  a  regular multi-head configuration.  If Xinerama is enabled
       (e.g., with +xinerama on the command line), the clients  see  a  single
       large screen.

       Xdmx  communicates  to  the  back-end  X servers using the standard X11
       protocol, and standard and/or commonly available X server extensions.


       In addition to the normal X server options described in the  Xserver(1)
       manual page, Xdmx accepts the following command line switches:

       -display display-name
               This  specifies the name(s) of the back-end X server display(s)
               to connect to.  This option may be specified multiple times  to
               connect  to  more than one back-end display.  The first is used
               as screen 0, the second as screen 1, etc.  If  this  option  is
               omitted,  the  $DISPLAY  environment  variable  is  used as the
               single back-end X server display.

       -xinput input-source
               This specifies the source to use for XInput extension  devices.
               The  choices  are  the  same  as  for -input , described below,
               except that core devices on backend servers cannot  be  treated
               as  XInput  extension  devices.  (Although extension devices on
               backend and console servers are supported as extension  devices
               under Xdmx).

       -input input-source
               This  specifies  the  source to use for the core input devices.
               The choices are:

                   A set of dummy core input drivers are  used.   These  never
                   generate any input events.

                   The  raw  keyboard  and pointer from the local computer are
                   used.  A  comma-separated  list  of  driver  names  can  be
                   appended.    For  example,  to  select  the  example  Linux
                   keyboard and PS/2 mouse driver use:  -input  local,kbd,ps2.
                   The following drivers have been implemented for Linux: kbd,
                   ms (a two-button Microsoft mouse driver), ps2 (a PS/2 mouse
                   driver),  usb-mou  (a  USB  mouse  driver),  usb-kbd (a USB
                   keyboard driver), and usb-oth  (a  USB  non-keyboard,  non-
                   mouse  driver).   Additional  drivers may be implemented in
                   the future.  Appropriate defaults will be used if no comma-
                   separated list is provided.

                   If  the  display-name is a back-end server, then core input
                   events are taken from the server specified.   Otherwise,  a
                   console window will be opened on the specified display.

                   If  the  display-name  is  followed  by  ",xi"  then XInput
                   extension devices on the  display  will  be  used  as  Xdmx
                   XInput  extension devices.  If the display-name is followed
                   by ",noxi" then XInput extension  devices  on  the  display
                   will   not  be  used  as  Xdmx  XInput  extension  devices.
                   Currently, the default is ",xi".

                   If the display-name  is  followed  by  ",console"  and  the
                   display-name  refers to a display that is used as a backend
                   display, then a console  window  will  be  opened  on  that
                   display  and  that  display  will  be  treated as a backend
                   display.  Otherwise  (or  if  ",noconsole"  is  used),  the
                   display  will  be  treated purely as a backend or a console
                   display, as described above.

                   If  the  display-name  is  followed  by  ",windows",   then
                   outlines  of  the  windows on the backend will be displayed
                   inside the console window.  Otherwise (or  if  ",nowindows"
                   is  used), the console window will not display the outlines
                   of backend windows.  (This option only applies  to  console

                   If  the display-name is followed by ",xkb", then the next 1
                   to 3 comma-separated parameters will specify the  keycodes,
                   symbols,  and  geometry  of  the  keyboard  for  this input
                   device.  For  example,  ",xkb,xfree86,pc104"  will  specify
                   that  the "xfree86" keycodes and the "pc104" symbols should
                   be used to initialize the keyboard.  For an  SGI  keyboard,
                   ",xkb,sgi/indy(pc102)"   might   be   useful.   A  list  of
                   keycodes,  symbols,  and  geometries  can   be   found   in
                   /usr/share/X11/xkb.    Use   of   keycodes,   symbols   and
                   geometries for XKB configuration is deprecated in favor  of
                   the  rules,  layout,  model,  variant  and options settings
                   available via the -param  command  line  switch.   If  this
                   option  is not specified, the input device will be queried,
                   perhaps using the XKEYBOARD extension.

               If this option isn't specified, the default input source is the
               first back-end server (the one used for screen 0).  The console
               window shows the layout of the back-end display(s) and  pointer
               movements  and  key  presses  within the console window will be
               used as core input devices.

               Several special function keys  are  active,  depending  on  the
               input source:

                      Ctrl-Alt-q will terminate the Xdmx server in all modes.

                      Ctrl-Alt-g  will toggle a server grab in console mode (a
                      special cursor, currently a spider, is used to  indicate
                      an active server grab).

                      Ctrl-Alt-f will toggle fine-grain motion in console mode
                      (a special cursor, currently a cross hair,  is  used  to
                      indicate  this  mode).   If this mode is combined with a
                      server grab, then the cursor will have 4  lines  instead
                      of only 2.

                      Ctrl-Alt-F1  through Ctrl-Alt-F12 will switch to another
                      VC in local (raw) mode.

               This option turns on (legacy)  support  for  the  shadow  frame

               This  option  turns  off  (legacy) support for the shadow frame
               buffer.  Note that this option has been deprecated and will  be
               removed in the next release.

               This  option  turns off support for displaying multiple cursors
               on overlapped back-end displays.  This option is available  for
               testing and benchmarking purposes.

               This  option  sets  the  Xdmx server's default font path.  This
               option can be specified multiple times to accommodate  multiple
               font  paths.   See  the  FONT  PATHS  section  below  for  very
               important information regarding setting the default font path.

       -configfile filename
               Specify the configuration file that should be read.  Note  that
               if   the   -display  command-line  option  is  used,  then  the
               configuration file will be ignored.

       -config name
               Specify a configuration to use.  The  name  will  be  the  name
               following the virtual keyword in the configuration file.

       -stat interval screens
               This option enables the display of performance statistics.  The
               interval is in seconds.  The screens is a count of  the  number
               of  back-end  screens  for which data is printed each interval.
               Specifying 0 for screens will display data for all screens.

               For each screen, the  following  information  is  printed:  the
               screen number, an absolute count of the number of XSync() calls
               made (SyncCount), the rate of these calls during  the  previous
               interval    (Sync/s),   the   average   round-trip   time   (in
               microseconds) of  the  last  10  XSync()  calls  (avSync),  the
               maximum  round-trip time (in microseconds) of the last 10 XSync
               calls (mxSync), the average number  of  XSync()  requests  that
               were  pending  but  not  yet  processed for each of the last 10
               processed XSync() calls, the maximum number of XSync() requests
               that were pending but not yet processed for each of the last 10
               processed  XSync()  calls,  and   a   histogram   showing   the
               distribution of the times of all of the XSync() calls that were
               made during the previous interval.

               (The length of the moving average and the number and  value  of
               histogram   bins  are  configurable  at  compile  time  in  the
               dmxstat.h header file.)

       -syncbatch interval
               This option sets  the  interval  in  milliseconds  for  XSync()
               batching.   An  interval  less  than or equal to 0 will disable
               XSync() batching.  The default interval is 100 ms.

               This option disables the  offscreen  optimization.   Since  the
               lazy   window  creation  optimization  requires  the  offscreen
               optimization to be enabled, this option will also  disable  the
               lazy window creation optimization.

               This option disables the lazy window creation optimization.

               This option disables the primitive subdivision optimization.

       -noxkb  Disable  use  of  the  XKB extension for communication with the
               back end displays.  (Combine with -kb to  disable  all  use  of

       -depth int
               This  option  sets  the  root  window's  default  depth.   When
               choosing a default visual from those available on the  back-end
               X  server,  the  first  visual  with  that  matches  the  depth
               specified is used.

               This  option  can  be  combined  with  the  -cc  option,  which
               specifies the default color visual class, to force the use of a
               specific depth and color class for the root window.

               This option disables the RENDER extension.

               This option disables GLX proxy -- the  build-in  GLX  extension
               implementation that is DMX aware.

               This option disables the swap group and swap barrier extensions
               in GLX proxy.

               This option enables synchronization after a swap  buffers  call
               by  waiting  until  all  X protocol has been processed.  When a
               client  issues  a  glXSwapBuffers  request,  Xdmx  relays  that
               request  to  each  back-end  X  server,  and those requests are
               buffered along with all other protocol requests.   However,  in
               systems  that  have  large  network buffers, this buffering can
               lead to the set of back-end X servers handling the swap buffers
               request  asynchronously.   With this option, an XSync() request
               is issued to each back-end X  server  after  sending  the  swap
               buffers  request.  The XSync() requests will flush all buffered
               protocol (including the swap buffers requests) and  wait  until
               the  back-end  X  servers  have processed those requests before
               continuing.  This option does not wait until  all  GL  commands
               have  been  processed  so  there  might  be  previously  issued
               commands that are still being processed in the GL pipe when the
               XSync()  request  returns.  See the -glxfinishswap option below
               if Xdmx should wait until the GL commands have been processed.

               This option enables synchronization after a swap  buffers  call
               by  waiting  until  all GL commands have been completed.  It is
               similar to the -glxsyncswap option above; however,  instead  of
               issuing  an  XSync(),  it  issues  a glFinish() request to each
               back-end X server after sending the swap buffers requests.  The
               glFinish()  request  will flush all buffered protocol requests,
               process both X and GL requests, and wait until  all  previously
               called GL commands are complete before returning.

               This  option  ignores  font paths that are not available on all
               back-end servers by removing the  bad  font  path(s)  from  the
               default  font path list.  If no valid font paths are left after
               removing the bad paths, an error to that effect is  printed  in
               the log.

               This  option  enables  the  dynamic  addition  and  removal  of
               screens, which is disabled by default.  Note that GLXProxy  and
               Render  do  not  yet  support  dynamic  addition and removal of
               screens, and must be disabled via the -noglxproxy and -norender
               command line options described above.

       -param  This   option   specifies   parameters  on  the  command  line.
               Currently, only parameters dealing with XKEYBOARD configuration
               are  supported.   These  parameters  apply  only  to  the  core
               keyboard.  Parameter values are installation-dependent.  Please
               see  /usr/share/X11/xkb  or  a  similar  directory for complete

                       Defaults to "evdev".  Other values  may  include  "sgi"
                       and "sun".

                       Defaults  to  "pc105".   When  used  with "base" rules,
                       other values may include "pc102", "pc104", "microsoft",
                       and  many  others.   When  used with "sun" rules, other
                       values may include "type4" and "type5".

                       Defaults to "us".  Other country codes and "dvorak" are
                       usually available.

                       Defaults to "".

                       Defaults to "".


       The following words and tokens are reserved:
              virtual display wall option param { } ; #

       Comments  start  with a # mark and extend to the end of the line.  They
       may appear anywhere.  If a configuration file is read into  xdmxconfig,
       the comments in that file will be preserved, but will not be editable.

       The grammar is as follows:
              virtual-list ::= [ virtual-list ] | virtual

              virtual ::= virtual [ name ] [ dim ] { dw-list }

              dw-list ::= [ dw-list ] | dw

              dw ::= display | wall | option

              display  ::= display name [ geometry ] [ / geometry ] [ origin ]

              wall ::= wall [ dim ] [ dim ] name-list ;

              option ::= option name-list ;

              param ::= param name-list ;

              param ::= param { param-list }

              param-list ::= [ param-list ] | name-list ;

              name-list ::= [ name-list ] | name

              name ::= string | double-quoted-string

              dim ::= integer x integer

              geometry ::= [ integer x  integer  ]  [  signed-integer  signed-
              integer ]

              origin ::= @ integer x integer

       The   name   following  virtual  is  used  as  an  identifier  for  the
       configuration, and may be passed to Xdmx using the -config command line
       option.   The  name  of  a  display  should be standard X display name,
       although no checking is performed (e.g., "machine:0").

       For names, double quotes are optional unless the name  is  reserved  or
       contains spaces.

       The  first  dimension following wall is the dimension for tiling (e.g.,
       2x4 or 4x4).  The second dimension following wall is the  dimension  of
       each display in the wall (e.g., 1280x1024).

       The  first  geometry  following  display  is the geometry of the screen
       window on the backend server.  The second  geometry,  which  is  always
       preceeded  by a slash, is the geometry of the root window.  By default,
       the root window has the same geometry as the screen window.

       The option line can be used to specify any command-line options  (e.g.,
       -input).   (It  cannot  be  used  to  specify the name of the front-end
       display.)  The option line is processed once at  server  startup,  just
       line command line options.  This behavior may be unexpected.


       Two  displays  being  used for a desktop may be specified in any of the
       following formats:
              virtual example0 {
                  display d0:0 1280x1024 @0x0;
                  display d1:0 1280x1024 @1280x0;

              virtual example1 {
                  display d0:0 1280x1024;
                  display d1:0 @1280x0;

              virtual example2 {
                  display "d0:0";
                  display "d1:0" @1280x0;

              virtual example3 { wall 2x1 d0:0 d1:0; }
       A 4x4 wall of 16 total displays could be specified as  follows  (if  no
       tiling dimension is specified, an approximate square is used):
              virtual example4 {
                  wall d0:0 d1:0 d2:0 d3:0
                       d4:0 d5:0 d6:0 d7:0
                       d8:0 d9:0 da:0 db:0
                       dc:0 dd:0 de:0 df:0;


       The  font  path used by the Xdmx front-end server will be propagated to
       each back-end server,which requires  that  each  back-end  server  have
       access  to the exact same font paths as the front-end server.  This can
       be most easily handled by either using a font server (e.g., xfs) or  by
       remotely  mounting  the  font  paths  on each back-end server, and then
       setting the Xdmx server's default font path  with  the  -I  "-fontpath"
       command line option described above.

       For  example,  if  you  specify  a font path with the following command
              Xdmx :1  -display  d0:0  -fontpath  /usr/fonts/75dpi/  -fontpath
              /usr/fonts/Type1/ +xinerama
       Then,  /usr/fonts/75dpi/ and /usr/fonts/Type1/ must be valid font paths
       on the Xdmx server and  all  back-end  server,  which  is  d0  in  this

       Font  servers  can  also  be  specified with the -fontpath option.  For
       example, let's assume that a properly configured font server is running
       on host d0.  Then, the following command line
              Xdmx  :1  -display  d0:0  -display  d1:0  -fontpath  tcp/d0:7100
       will initialize the front-end Xdmx server  and  each  of  the  back-end
       servers to use the font server on d0.

       Some  fonts might not be supported by either the front-end or the back-
       end servers.  For example,  let's  assume  the  front-end  Xdmx  server
       includes support Type1 fonts, but one of the back-end servers does not.
       Let's also assume that the default font path for  Xdmx  includes  Type1
       fonts  in  its font path.  Then, when Xdmx initializes the default font
       path to load the default font, the font path that includes Type1  fonts
       (along  with  the  other  default  font paths that are used by the Xdmx
       server) is sent to the back-end server that cannot handle Type1  fonts.
       That back-end server then rejects the font path and sends an error back
       to the Xdmx server.  Xdmx  then  prints  an  error  message  and  exits
       because  it failed to set the default font path and was unable load the
       default font.

       To fix this error, the offending font path must  be  removed  from  the
       default font path by using a different -fontpath command line option.

       The  -fontpath  option  can  also be added to the configuration file as
       described above.


       The back-end machines are d0 and d1, core input is from the pointer and
       keyboard attached to d0, clients will refer to :1 when opening windows:
              Xdmx :1 -display d0:0 -display d1:0 +xinerama

       As above, except with core input from d1:
              Xdmx :1 -display d0:0 -display d1:0 -input d1:0 +xinerama

       As  above,  except  with  core input from a console window on the local
              Xdmx :1 -display d0:0 -display d1:0 -input :0 +xinerama

       As above, except with core input from the local keyboard and mouse:
              Xdmx  :1  -display  d0:0  -display  d1:0  -input   local,kbd,ps2
       Note  that  local input can be used under Linux while another X session
       is running on :0 (assuming the user can access the  Linux  console  tty
       and mouse devices): a new (blank) VC will be used for keyboard input on
       the local machine and the Ctrl-Alt-F* sequence  will  be  available  to
       change to another VC (possibly back to another X session running on the
       local  machine).   Using  Ctrl-Alt-Backspace  on  the  blank  VC   will
       terminate the Xdmx session and return to the original VC.

       This example uses the configuration file shown in the previous section:
              Xdmx   :1  -input  :0  +xinerama  -configfile  filename  -config
       With this configuration file line:
              option -input :0 +xinerama;
       the command line can be shortened to:
              Xdmx :1 -configfile filename -config example2


       The USB  device  drivers  use  the  devices  called  /dev/input/event0,
       /dev/input/event1,  etc.   under Linux.  These devices are driven using
       the evdev Linux kernel module, which is part of the hid suite.   Please
       note that if you load the mousedev or kbddev Linux kernel modules, then
       USB devices will appear as core Linux input devices and you will not be
       able  to select between using the device only as an Xdmx core device or
       an Xdmx XInput extension device.  Further, you may be unable to  unload
       the  mousedev  Linux  kernel  module  if  XFree86  is configured to use
       /dev/input/mice as an input device (this is quite  helpful  for  laptop
       users  and  is  set  up  by default under some Linux distributions, but
       should be changed if USB devices are to be used with Xdmx).

       The USB device drivers search through the Linux devices for  the  first
       mouse,  keyboard,  or  non-mouse-non-keyboard Linux device and use that


       If Xdmx was invoked with -xkb or was not compiled to use the  XKEYBOARD
       extension,  then a keyboard on a backend or console will be initialized
       using the map that the host X server provides.

       If the XKEYBOARD extension is used for both Xdmx and the host X  server
       for the keyboard (i.e., the backend or console X server), then the type
       of the keyboard will be  obtained  from  the  host  X  server  and  the
       keyboard   under  Xdmx  will  be  initialized  with  that  information.
       Otherwise, the default type of keyboard will be initialized.   In  both
       cases,  the  map  from  the host X server will not be used.  This means
       that  different  initial  behavior  may  be  noted  with  and   without
       XKEYBOARD.  Consistent and expected results will be obtained by running
       XKEYBOARD on all servers and by avoiding the  use  of  xmodmap  on  the
       backend or console X servers prior to starting Xdmx.

       If  -xkbmap  is  specified on the Xdmx command line, then that map will
       currently be used for all keyboards.


       X was not designed to support multiple core keyboards.   However,  Xdmx
       provides  some  support for multiple core keyboards.  Best results will
       be obtained if all of the keyboards are of the same type and are  using
       the  same  keyboard  map.   Because  the  X  server passes raw key code
       information to the X client, key symbols for keyboards  with  different
       key  maps would be different if the key code for each keyboard was sent
       without translation to the client.  Therefore,  Xdmx  will  attempt  to
       translate the key code from a core keyboard to the key code for the key
       with the same key symbol of the first core keyboard  that  was  loaded.
       If  the  key symbol appears in both maps, the results will be expected.
       Otherwise, the second core keyboard will return a NoSymbol  key  symbol
       for  some keys that would have been translated if it was the first core


       DMX(3),   X(7),   Xserver(1),   xdmxconfig(1),   vdltodmx(1),   xfs(1),
       xkbcomp(1), xkeyboard-config(7)


       Kevin  E.  Martin <>, David H. Dawes <>,
       and Rickard E. (Rik) Faith <>.

       Portions  of  Xdmx  are  based  on  code  from  The   XFree86   Project
       ( and X.Org (