Provided by: xvfb_21.1.4-2ubuntu1.7~22.04.10_amd64 bug


       Xvfb - virtual framebuffer X server for X Version 11


       Xvfb [ option ] ...


       Xvfb  is  an  X  server  that can run on machines with no display hardware and no physical
       input devices.  It emulates a dumb framebuffer using virtual memory.

       The primary use of this server was intended to be server testing.  The  fb  code  for  any
       depth  can  be exercised with this server without the need for real hardware that supports
       the desired depths.  The X community has found many other novel uses for  Xvfb,  including
       testing  clients  against unusual depths and screen configurations, doing batch processing
       with Xvfb as a background rendering engine, load testing, as  an  aid  to  porting  the  X
       server  to a new platform, and providing an unobtrusive way to run applications that don't
       really need an X server but insist on having one anyway.


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

       -screen screennum WxHxD
           This  option  creates  screen screennum and sets its width, height, and depth to W, H,
           and D respectively.   By  default,  only  screen  0  exists  and  has  the  dimensions

       -pixdepths list-of-depths
           This  option  specifies  a  list  of  pixmap  depths that the server should support in
           addition to the depths implied by the supported screens.  list-of-depths is  a  space-
           separated list of integers that can have values from 1 to 32.

       -fbdir framebuffer-directory
           This  option  specifies  the directory in which the memory mapped files containing the
           framebuffer memory should be created.  See FILES.  This option only exists on machines
           that have the mmap and msync system calls.

           This option specifies that the framebuffer should be put in shared memory.  The shared
           memory ID for each screen will be printed by the server.  The shared memory is in  xwd
           format.   This  option only exists on machines that support the System V shared memory

       If neither -shmem nor -fbdir is specified, the framebuffer memory will be  allocated  with

       -linebias n
           This  option specifies how to adjust the pixelization of thin lines.  The value n is a
           bitmask of octants in which to prefer an axial step when the Bresenham error  term  is
           exactly  zero.  See the file Xserver/mi/miline.h for more information.  This option is
           probably only useful to server  developers  to  experiment  with  the  range  of  line
           pixelization possible with the fb code.

       -blackpixel pixel-value, -whitepixel pixel-value
           These options specify the black and white pixel values the server should use.


       The following files are created if the -fbdir option is given.

           Memory mapped file containing screen n's framebuffer memory, one file per screen.  The
           file is in xwd format.  Thus, taking a full-screen snapshot can be done  with  a  file
           copy command, and the resulting snapshot will even contain the cursor image.


       Xvfb :1 -screen 0 1600x1200x24
               The  server  will  listen for connections as server number 1, and screen 0 will be
               depth 24 1600x1200.

       Xvfb :1 -screen 1 1600x1200x16
               The server will listen for connections as server number 1, screen 0 will have  the
               default  screen  configuration  (1280x1024x24),  and  screen  1  will  be depth 16

       Xvfb -pixdepths 3 27 -fbdir /var/tmp
               The server will listen for connections as server number 0, will have  the  default
               screen  configuration  (one screen, 1280x1024x24), will also support pixmap depths
               of 3 and 27, and will use memory mapped files in /var/tmp for the framebuffer.

       xwud -in /var/tmp/Xvfb_screen0
               Displays screen 0 of the server started by the preceding example.


       X(7), Xserver(1), xwd(1), xwud(1), XWDFile.h


       David P. Wiggins, The Open Group, Inc.