Xvfb - virtual framebuffer X server for X Version 11
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
In addition to the normal server options described in the
Xserver(1) manual page, Xvfb accepts the following command
- -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 1280x1024x24.
- -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
- 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 interface.
If neither -shmem nor -fbdir is specified, the
framebuffer memory will be allocated with malloc().
- -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
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 1600x1200.
- 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.