Provided by: xdmx_1.15.1-0ubuntu2.11_amd64 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

       -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

                   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 input.)

                   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)

               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

       -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

               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 XKB.)

       -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

               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 information.

                       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.,

       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


       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 line:
              Xdmx  :1  -display  d0:0  -fontpath  /usr/fonts/75dpi/  -fontpath /usr/fonts/Type1/
       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 example.

       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
              Xdmx :1 -display d0:0 -display d1:0 -fontpath tcp/d0:7100 +xinerama
       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 display:
              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 +xinerama
       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 example2
       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 device.


       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

       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 keyboard.


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


       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 (