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           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 pro-
           tocol, 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 sin-
                   gle 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 key-
                       If the display-name is followed by ",xi" then XInput exten-
                       sion 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  dis-
                       play-name  refers  to  a  display that is used as a backend
                       display, then a console window will be opened on that  dis-
                       play 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  out-
                       lines  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 key-
                       codes,  symbols,   and   geometries   can   be   found   in
                       /usr/share/X11/xkb.   Use  of  keycodes, symbols and geome-
                       tries for XKB configuration is deprecated in favor  of  the
                       rules,  layout,  model, variant and options settings avail-
                       able 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).
                   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  impor-
                   tant 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  configu-
                   ration file will be ignored.
           -config name
                   Specify a configuration to use.  The name will be the name fol-
                   lowing 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  microsec-
                   onds) 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.
                   mization  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  choos-
                   ing  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 speci-
                   fies the default color visual class, to force the use of a spe-
                   cific 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
                   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.  Cur-
                   rently, only parameters dealing  with  XKEYBOARD  configuration
                   are  supported.   These  parameters apply only to the core key-
                   board.  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 "".
                  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-inte-
                  ger ]
                  origin ::= @ integer x integer
           The name following virtual is used as an identifier for the  configura-
           tion,  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 win-
           dow  on  the backend server.  The second geometry, which is always pre-
           ceeded 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  dis-
           play.)   The option line is processed once at server startup, just line
           command line options.  This behavior may be unexpected.


                      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 set-
           ting  the  Xdmx server's default font path with the -I "-fontpath" com-
           mand 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 exam-
           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  +xin-
           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
                  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  +xin-
           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  termi-
           nate 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  exam-
           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 key-
           board 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
           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), xkb-
           comp(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 (

    X Version 11 xorg-server 1.11.3 Xdmx(1)


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