Xdmx



Xdmx(1)                                                                Xdmx(1)




NAME

       Xdmx - Distributed Multi-head X server


SYNOPSIS

       Xdmx [:display] [option ...]


DESCRIPTION

       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.


OPTIONS

       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:

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


               local
                   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-
                   board 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 key-
                   board 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.


               display-name
                   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 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
                   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 key-
                   codes,  symbols,   and   geometries   can   be   found   in
                   /usr/X11R6/lib/X11/xkb.   If  this option is not specified,
                   the input device will be queried, perhaps using  the  XKEY-
                   BOARD 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.


       -shadowfb
               This option turns on (legacy)  support  for  the  shadow  frame
               buffer.


       -noshadowfb
               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.


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


       -fontpath
               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.

               (The length of the moving average and the number and  value  of
               histogram  bins  are  configurable at compile time in the dmxs-
               tat.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.


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


       -nowindowopt
               This option disables the lazy window creation optimization.


       -nosubdivprims
               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 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.


       -norender
               This option disables the RENDER extension.


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


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


       -glxsyncswap
               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 com-
               mands 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.


       -glxfinishswap
               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.


       -ignorebadfontpaths
               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.


       -addremovescreens
               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/X11R6/lib/X11/xkb or a similar directory for  complete
               information.

               XkbRules
                       Defaults  to "xfree86".  Other values may include "sgi"
                       and "sun".


               XkbModel
                       Defaults to "pc101".  When used with  "xfree86"  rules,
                       other  values  may  include  "pc102", "pc104", "pc105",
                       "microsoft", and many others.   When  used  with  "sun"
                       rules, other values may include "type4" and "type5".


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


               XkbVariant
                       Defaults to "".


               XkbOptions
                       Defaults to "".


CONFIGURATION FILE GRAMMAR

       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-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.


CONFIGURATION FILE EXAMPLES

       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;
              }


FONT PATHS

       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
       line:
              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-
       ple.

       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-
              erama
       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.


COMMAND-LINE EXAMPLES

       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 +xin-
              erama
       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-
              ple2
       With this configuration file line:
              option -input :0 +xinerama;
       the command line can be shortened to:
              Xdmx :1 -configfile filename -config example2


USING THE USB DEVICE DRIVERS

       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.


KEYBOARD INITIALIZATION

       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
       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.


MULTIPLE CORE 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 infor-
       mation 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.


SEE ALSO

       DMX(3X), X(__miscmansuffix__), Xserver(1), xdmxconfig(1),  vdltodmx(1),
       xfs(1), xkbcomp(1)


AUTHORS

       Kevin  E.  Martin <kem@redhat.com>, David H. Dawes <dawes@xfree86.org>,
       and Rickard E. (Rik) Faith <faith@redhat.com>.

       Portions  of  Xdmx  are  based  on  code  from  The   XFree86   Project
       (http://www.xfree86.org) and X.Org (http://www.x.org).



X.Org                            Version 6.8.2                         Xdmx(1)

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