Section: User Commands (1)
Updated: xorg-server 1.20.10
Xserver - X Window System display server
is the generic name for the X Window System display server. It is
frequently a link or a copy of the appropriate server binary for
driving the most frequently used server on a given machine.
STARTING THE SERVER
The X server is usually started from the X Display Manager program
(1) or a similar display manager program.
This utility is run from the system boot files and takes care of keeping
the server running, prompting for usernames and passwords, and starting up
the user sessions.
Installations that run more than one window system may need to use the
xinit(1) utility instead of a display manager. However, xinit is
to be considered a tool for building startup scripts and is not
intended for use by end users. Site administrators are strongly
urged to use a display manager, or build other interfaces for novice users.
The X server may also be started directly by the user, though this
method is usually reserved for testing and is not recommended for
normal operation. On some platforms, the user must have special
permission to start the X server, often because access to certain
devices (e.g. /dev/mouse) is restricted.
When the X server starts up, it typically takes over the display. If
you are running on a workstation whose console is the display, you may
not be able to log into the console while the server is running.
Many X servers have device-specific command line options. See the manual
pages for the individual servers for more details; a list of
server-specific manual pages is provided in the SEE ALSO section below.
All of the X servers accept the command line options described below.
Some X servers may have alternative ways of providing the parameters
described here, but the values provided via the command line options
should override values specified via other mechanisms.
The X server runs as the given displaynumber, which by default is 0.
If multiple X servers are to run simultaneously on a host, each must have
a unique display number. See the DISPLAY
NAMES section of the X(7) manual page to learn how to
specify which display number clients should try to use.
- -a number
sets pointer acceleration (i.e. the ratio of how much is reported to how much
the user actually moved the pointer).
disables host-based access control mechanisms. Enables access by any host,
and permits any host to modify the access control list.
Use with extreme caution.
This option exists primarily for running test suites remotely.
- -audit level
sets the audit trail level. The default level is 1, meaning only connection
rejections are reported. Level 2 additionally reports all successful
connections and disconnects. Level 4 enables messages from the
SECURITY extension, if present, including generation and revocation of
authorizations and violations of the security policy.
Level 0 turns off the audit trail.
Audit lines are sent as standard error output.
- -auth authorization-file
specifies a file which contains a collection of authorization records used
to authenticate access. See also the xdm(1) and
Xsecurity(7) manual pages.
- -background none
Asks the driver not to clear the background on startup, if the driver supports that.
May be useful for smooth transition with eg. fbdev driver.
For security reasons this is not the default as the screen contents might
show a previous user session.
sets the default root window to solid black instead of the standard root weave
pattern. This is the default unless -retro or -wr is specified.
disables backing store support on all screens.
turns off key-click.
- c volume
sets key-click volume (allowable range: 0-100).
- -cc class
sets the visual class for the root window of color screens.
The class numbers are as specified in the X protocol.
Not obeyed by all servers.
causes the server to generate a core dump on fatal errors.
- -displayfd fd
specifies a file descriptor in the launching process. Rather than specify
a display number, the X server will attempt to listen on successively higher
display numbers, and upon finding a free one, will write the display number back
on this file descriptor as a newline-terminated string. The -pn option is
ignored when using -displayfd.
- -deferglyphs whichfonts
specifies the types of fonts for which the server should attempt to use
deferred glyph loading. whichfonts can be all (all fonts),
none (no fonts), or 16 (16 bit fonts only).
- -dpi resolution
sets the resolution for all screens, in dots per inch.
To be used when the server cannot determine the screen size(s) from the
enables DPMS (display power management services), where supported. The
default state is platform and configuration specific.
disables DPMS (display power management services). The default state
is platform and configuration specific.
disables named extension. If an unknown extension name is specified,
a list of accepted extension names is printed.
enables named extension. If an unknown extension name is specified,
a list of accepted extension names is printed.
- -f volume
sets beep (bell) volume (allowable range: 0-100).
- -fc cursorFont
sets default cursor font.
- -fn font
sets the default font.
- -fp fontPath
sets the search path for fonts. This path is a comma separated list
of directories which the X server searches for font databases.
See the FONTS section of this manual page for more information and the default
prints a usage message.
causes all remaining command line arguments to be ignored.
Prohibit creating indirect GLX contexts. Indirect GLX is of limited use,
since it lacks support for many modern OpenGL features and extensions;
it's slower than direct contexts; and it opens a large attack surface for
protocol parsing errors.
This is the default unless +iglx is specified.
Allow creating indirect GLX contexts.
- -maxbigreqsize size
sets the maximum big request to
disable the display of the pointer cursor.
- -nolisten trans-type
disables a transport type. For example, TCP/IP connections can be disabled
This option may be issued multiple times to disable listening to different
Supported transport types are platform dependent, but commonly include:
|tcp TCP over IPv4 or IPv6|
|inet TCP over IPv4 only|
|inet6 TCP over IPv6 only|
|unix UNIX Domain Sockets|
|local Platform preferred local connection method|
- -listen trans-type
enables a transport type. For example, TCP/IP connections can be enabled
This option may be issued multiple times to enable listening to different
prevents a server reset when the last client connection is closed. This
overrides a previous
command line option.
- -p minutes
sets screen-saver pattern cycle time in minutes.
permits the server to continue running if it fails to establish all of
its well-known sockets (connection points for clients), but
establishes at least one. This option is set by default.
causes the server to exit if it fails to establish all of its well-known
sockets (connection points for clients).
turns off auto-repeat.
turns on auto-repeat.
starts the server with the classic stipple and cursor visible. The default
is to start with a black root window, and to suppress display of the cursor
until the first time an application calls XDefineCursor(). For kdrive
servers, this implies -zap.
- -s minutes
sets screen-saver timeout time in minutes.
disables save under support on all screens.
- -seat seat
seat to run on. Takes a string identifying a seat in a platform
specific syntax. On platforms which support this feature this may be
used to limit the server to expose only a specific subset of devices
connected to the system.
- -t number
sets pointer acceleration threshold in pixels (i.e. after how many pixels
pointer acceleration should take effect).
causes the server to terminate at server reset, instead of continuing to run.
This overrides a previous
command line option.
- -to seconds
sets default connection timeout in seconds.
disables all testing extensions (e.g., XTEST, XTrap, XTestExtension1, RECORD).
ignored, for servers started the ancient way (from init).
sets video-off screen-saver preference.
sets video-on screen-saver preference.
forces the default backing-store of all windows to be WhenMapped. This
is a backdoor way of getting backing-store to apply to all windows.
Although all mapped windows will have backing store, the backing store
attribute value reported by the server for a window will be the last
value established by a client. If it has never been set by a client,
the server will report the default value, NotUseful. This behavior is
required by the X protocol, which allows the server to exceed the
client's backing store expectations but does not provide a way to tell
the client that it is doing so.
sets the default root window to solid white instead of the standard root weave
- -x extension
loads the specified extension at init.
This is a no-op for most implementations.
enables(+) or disables(-) the XINERAMA extension. The default state is
platform and configuration specific.
SERVER DEPENDENT OPTIONS
Some X servers accept the following options:
- -ld kilobytes
sets the data space limit of the server to the specified number of kilobytes.
A value of zero makes the data size as large as possible. The default value
of -1 leaves the data space limit unchanged.
- -lf files
sets the number-of-open-files limit of the server to the specified number.
A value of zero makes the limit as large as possible. The default value
of -1 leaves the limit unchanged.
- -ls kilobytes
sets the stack space limit of the server to the specified number of kilobytes.
A value of zero makes the stack size as large as possible. The default value
of -1 leaves the stack space limit unchanged.
Set the maximum number of clients allowed to connect to the X server.
Acceptable values are 64, 128, 256 or 512.
sets the color allocation policy that will be used by the render extension.
selects the default policy defined for the display depth of the X
don't use any color cell.
use a gray map of 13 color cells for the X render extension.
use a color cube of at most 4*4*4 colors (that is 64 color cells).
disables smart scheduling on platforms that support the smart scheduler.
- -schedInterval interval
sets the smart scheduler's scheduling interval to
X servers that support XDMCP have the following options.
See the X Display Manager Control Protocol
specification for more
- -query hostname
enables XDMCP and sends Query packets to the specified
enable XDMCP and broadcasts BroadcastQuery packets to the network. The
first responding display manager will be chosen for the session.
- -multicast [address [hop count]]
Enable XDMCP and multicast BroadcastQuery packets to the network.
The first responding display manager is chosen for the session. If an
address is specified, the multicast is sent to that address. If no
address is specified, the multicast is sent to the default XDMCP IPv6
multicast group. If a hop count is specified, it is used as the maximum
hop count for the multicast. If no hop count is specified, the multicast
is set to a maximum of 1 hop, to prevent the multicast from being routed
beyond the local network.
- -indirect hostname
enables XDMCP and send IndirectQuery packets to the specified
- -port port-number
uses the specified port-number for XDMCP packets, instead of the
default. This option must be specified before any -query, -broadcast,
-multicast, or -indirect options.
- -from local-address
specifies the local address to connect from (useful if the connecting host
has multiple network interfaces). The local-address may be expressed
in any form acceptable to the host platform's gethostbyname(3)
causes the server to terminate (rather than reset) when the XDMCP session
- -class display-class
XDMCP has an additional display qualifier used in resource lookup for
display-specific options. This option sets that value, by default it
is "MIT-unspecified" (not a very useful value).
- -cookie xdm-auth-bits
When testing XDM-AUTHENTICATION-1, a private key is shared between the
server and the manager. This option sets the value of that private
data (not that it is very private, being on the command line!).
- -displayID display-id
Yet another XDMCP specific value, this one allows the display manager to
identify each display so that it can locate the shared key.
X servers that support the XKEYBOARD (a.k.a. "XKB") extension accept the
following options. All layout files specified on the command line must be
located in the XKB base directory or a subdirectory, and specified as the
relative path from the XKB base directory. The default XKB base directory is
- [+-]accessx [ timeout [ timeout_mask [ feedback [ options_mask ] ] ] ]
enables(+) or disables(-) AccessX key sequences.
- -xkbdir directory
base directory for keyboard layout files. This option is not available
for setuid X servers (i.e., when the X server's real and effective uids
- -ardelay milliseconds
sets the autorepeat delay (length of time in milliseconds that a key must
be depressed before autorepeat starts).
- -arinterval milliseconds
sets the autorepeat interval (length of time in milliseconds that should
elapse between autorepeat-generated keystrokes).
- -xkbmap filename
loads keyboard description in filename on server startup.
The X server supports client connections via a platform-dependent subset of
the following transport types: TCP/IP, Unix Domain sockets,
and several varieties of SVR4 local connections. See the DISPLAY
NAMES section of the X
(7) manual page to learn how to
specify which transport type clients should try to use.
The X server implements a platform-dependent subset of the following
authorization protocols: MIT-MAGIC-COOKIE-1, XDM-AUTHORIZATION-1,
XDM-AUTHORIZATION-2, SUN-DES-1, and MIT-KERBEROS-5. See the
(7) manual page for information on the
operation of these protocols.
Authorization data required by the above protocols is passed to the
server in a private file named with the -auth command line
option. Each time the server is about to accept the first connection
after a reset (or when the server is starting), it reads this file.
If this file contains any authorization records, the local host is not
automatically allowed access to the server, and only clients which
send one of the authorization records contained in the file in the
connection setup information will be allowed access. See the
Xau manual page for a description of the binary format of this
file. See xauth(1) for maintenance of this file, and distribution
of its contents to remote hosts.
The X server also uses a host-based access control list for deciding
whether or not to accept connections from clients on a particular machine.
If no other authorization mechanism is being used,
this list initially consists of the host on which the server is running as
well as any machines listed in the file /etc/Xn.hosts, where
n is the display number of the server. Each line of the file should
contain either an Internet hostname (e.g. expo.lcs.mit.edu)
or a complete name in the format
family:name as described in the xhost(1) manual page.
There should be no leading or trailing spaces on any lines. For example:
Users can add or remove hosts from this list and enable or disable access
control using the xhost command from the same machine as the server.
If the X FireWall Proxy (xfwp) is being used without a sitepolicy,
host-based authorization must be turned on for clients to be able to
connect to the X server via the xfwp. If xfwp is run without
a configuration file and thus no sitepolicy is defined, if xfwp
is using an X server where xhost + has been run to turn off host-based
authorization checks, when a client tries to connect to this X server
via xfwp, the X server will deny the connection. See xfwp(1)
for more information about this proxy.
The X protocol intrinsically does not have any notion of window operation
permissions or place any restrictions on what a client can do; if a program can
connect to a display, it has full run of the screen.
X servers that support the SECURITY extension fare better because clients
can be designated untrusted via the authorization they use to connect; see
the xauth(1) manual page for details. Restrictions are imposed
on untrusted clients that curtail the mischief they can do. See the SECURITY
extension specification for a complete list of these restrictions.
Sites that have better
authentication and authorization systems might wish to make
use of the hooks in the libraries and the server to provide additional
The X server attaches special meaning to the following signals:
This signal causes the server to close all existing connections, free all
resources, and restore all defaults. It is sent by the display manager
whenever the main user's main application (usually an xterm or window
manager) exits to force the server to clean up and prepare for the next
This signal causes the server to exit cleanly.
This signal is used quite differently from either of the above. When the
server starts, it checks to see if it has inherited SIGUSR1 as SIG_IGN
instead of the usual SIG_DFL. In this case, the server sends a SIGUSR1 to
its parent process after it has set up the various connection schemes.
Xdm uses this feature to recognize when connecting to the server
The X server can obtain fonts from directories and/or from font servers.
The list of directories and font servers
the X server uses when trying to open a font is controlled
by the font path
The default font path is
A special kind of directory can be specified using the catalogue:
prefix. Directories specified this way can contain symlinks pointing to the
real font directories. See the FONTPATH.D section for details.
The font path can be set with the -fp option or by xset(1)
after the server has started.
You can specify a special kind of font path in the form catalogue:<dir>
The directory specified after the catalogue: prefix will be scanned for symlinks
and each symlink destination will be added as a local fontfile FPE.
The symlink can be suffixed by attributes such as 'unscaled', which
will be passed through to the underlying fontfile FPE. The only exception is
the newly introduced 'pri' attribute, which will be used for ordering
the font paths specified by the symlinks.
An example configuration:
75dpi:unscaled:pri=20 -> /usr/share/X11/fonts/75dpi
ghostscript:pri=60 -> /usr/share/fonts/default/ghostscript
misc:unscaled:pri=10 -> /usr/share/X11/fonts/misc
type1:pri=40 -> /usr/share/X11/fonts/Type1
type1:pri=50 -> /usr/share/fonts/default/Type1
This will add /usr/share/X11/fonts/misc as the first FPE with the attribute
'unscaled', second FPE will be /usr/share/X11/fonts/75dpi, also with
the attribute 'unscaled' etc. This is functionally equivalent to setting
the following font path:
Initial access control list for display number n
Bitmap font directories
Outline font directories
Unix domain socket for display number n
Error log file for display number n if run from init(8)
Default error log file if the server is run from xdm(1)
General information: X
X Window System Protocol,
The X Font Service Protocol,
X Display Manager Control Protocol
Fonts: bdftopcf(1), mkfontdir(1), mkfontscale(1),
xfs(1), xlsfonts(1), xfontsel(1), xfd(1),
X Logical Font Description Conventions
Security: Xsecurity(7), xauth(1), Xau(1),
xdm(1), xhost(1), xfwp(1),
Security Extension Specification
Starting the server: startx(1), xdm(1), xinit(1)
Controlling the server once started: xset(1), xsetroot(1),
xhost(1), xinput(1), xrandr(1)
Server-specific man pages:
Xorg(1), Xdmx(1), Xephyr(1), Xnest(1),
Xvfb(1), Xquartz(1), XWin(1).
Server internal documentation:
Definition of the Porting Layer for the X v11 Sample Server
The sample server was originally written by Susan Angebranndt, Raymond
Drewry, Philip Karlton, and Todd Newman, from Digital Equipment
Corporation, with support from a large cast. It has since been
extensively rewritten by Keith Packard and Bob Scheifler, from MIT.
Dave Wiggins took over post-R5 and made substantial improvements.