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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 1280x1024x8.
- 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 interface.
If neither -shmem nor -fbdir is specified, the framebuffer memory will be
allocated with malloc().
The following files are created if the -fbdir option is given.
- -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
- 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 1600x1200x32
- The server
will listen for connections as server number 1, and screen 0 will be depth
- Xvfb :1 -screen 1 1600x1200x16
- The server will listen for connections
as server number 1, will have the default screen configuration (one screen,
1280x1024x8), 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, 1280x1024x8),
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
screen 0 of the server started by the preceding example.
David P. Wiggins, The Open Group, Inc.
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