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Manual: Xserver

XSERVER(1) General Commands Manual XSERVER(1)

NAME
Xserver - X Window System display server

SYNOPSIS
X [option ...]

DESCRIPTION
X 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 xdm(1) or a similar display man‐
ager 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 re‐
stricted. Where applicable, the X server notifies systemd when it is ready to process requests.

When the X server starts up, it typically takes over the display. If you are running on a worksta‐
tion whose console is the display, you may not be able to log into the console while the server is
running.

OPTIONS
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 alter‐
native ways of providing the parameters described here, but the values provided via the command line
options should override values specified via other mechanisms.

:displaynumber
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 actu‐
ally moved the pointer).

-ac 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 pri‐
marily 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 de‐
fault as the screen contents might show a previous user session.

-br 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.

-bs disables backing store support on all screens.

+byteswappedclients
Allow connections from clients with an endianess different to that of the server. This is
the default unless -byteswappedclients is specified.

-byteswappedclients
Prohibit connections from clients with an endianess different to that of the server.

-c 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 speci‐
fied in the X protocol. Not obeyed by all servers.

-core 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-termi‐
nated 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 load‐
ing. 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 de‐
termine the screen size(s) from the hardware.

dpms enables DPMS (display power management services), where supported. The default state is
platform and configuration specific.

-dpms disables DPMS (display power management services). The default state is platform and config‐
uration specific.

-extensionextensionName
disables named extension. If an unknown extension name is specified, a list of accepted ex‐
tension names is printed.

+extensionextensionName
enables named extension. If an unknown extension name is specified, a list of accepted ex‐
tension names is printed.

-f volume
sets beep (bell) volume (allowable range: 0-100).

-fakescreenfps ps
sets fake presenter screen default fps (allowable range: 1-600).

-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 in‐
formation and the default list.

-help prints a usage message.

-I causes all remaining command line arguments to be ignored.

-iglx Prohibit creating indirect GLX contexts. Indirect GLX is of limited use, since it lacks sup‐
port 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.

+iglx Allow creating indirect GLX contexts.

-maxbigreqsize size
sets the maximum big request to size MB.

-nocursor
disable the display of the pointer cursor.

-nolisten trans-type
disables a transport type. For example, TCP/IP connections can be disabled with -nolisten
tcp. This option may be issued multiple times to disable listening to different transport
types. 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 with -listen tcp.
This option may be issued multiple times to enable listening to different transport types.

-noreset
prevents a server reset when the last client connection is closed. This overrides a previous
-terminate command line option.

-p minutes
sets screen-saver pattern cycle time in minutes.

-pn 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 de‐
fault.

-nopn causes the server to exit if it fails to establish all of its well-known sockets (connection
points for clients).

-r turns off auto-repeat.

r turns on auto-repeat.

-retro 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 applica‐
tion calls XDefineCursor(). For kdrive servers, this implies -zap.

-s minutes
sets screen-saver timeout time in minutes.

-su 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 accelera‐
tion should take effect).

-terminate [delay]
causes the server to terminate at server reset, instead of continuing to run. This overrides
a previous -noreset command line option. If a delay in seconds is specified, the server
waits for at least the delay. At the end of this grace period if no client is connected, the
server terminates immediately.

-tst disables all testing extensions (e.g., XTEST, XTrap, XTestExtension1, RECORD).

ttyxx ignored, for servers started the ancient way (from init).

v sets video-off screen-saver preference.

-v sets video-on screen-saver preference.

-wr sets the default root window to solid white instead of the standard root weave pattern.

-x extension
loads the specified extension at init. This is a no-op for most implementations.

[+-]xinerama
enables(+) or disables(-) the XINERAMA extension. The default state is platform and configu‐
ration 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.

-maxclients
64|128|256|512 Set the maximum number of clients allowed to connect to the X server. Accept‐
able values are 64, 128, 256 or 512.

-render default|mono|gray|color sets the color allocation policy that will be used by the render ex‐
tension.

default selects the default policy defined for the display depth of the X server.

mono don't use any color cell.

gray use a gray map of 13 color cells for the X render extension.

color use a color cube of at most 4*4*4 colors (that is 64 color cells).

-dumbSched
disables smart scheduling on platforms that support the smart scheduler.

-schedInterval interval
sets the smart scheduler's scheduling interval to interval milliseconds.

XDMCP OPTIONS
X servers that support XDMCP have the following options. See the X Display Manager Control Protocol
specification for more information.

-query hostname
enables XDMCP and sends Query packets to the specified hostname.

-broadcast
enable XDMCP and broadcasts BroadcastQuery packets to the network. The first responding dis‐
play manager will be chosen for the session.

-multicast [address [hop count]]
Enable XDMCP and multicast BroadcastQuery packets to the network. The first responding dis‐
play 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 pre‐
vent the multicast from being routed beyond the local network.

-indirect hostname
enables XDMCP and send IndirectQuery packets to the specified hostname.

-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 net‐
work interfaces). The local-address may be expressed in any form acceptable to the host
platform's gethostbyname(3) implementation.

-once causes the server to terminate (rather than reset) when the XDMCP session ends.

-class display-class
XDMCP has an additional display qualifier used in resource lookup for display-specific op‐
tions. 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 man‐
ager. 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 dis‐
play so that it can locate the shared key.

XKEYBOARD OPTIONS
X servers that support the XKEYBOARD (a.k.a. "XKB") extension accept the following options. All lay‐
out 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
/usr/lib/X11/xkb.

[+-]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 are different).

-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 au‐
torepeat-generated keystrokes).

-xkbmap filename
loads keyboard description in filename on server startup.

NETWORK CONNECTIONS
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.

GRANTING ACCESS
The X server implements a platform-dependent subset of the following authorization protocols: MIT-
MAGIC-COOKIE-1, XDM-AUTHORIZATION-1, SUN-DES-1, Host Access, and Server Interpreted. See the Xsecu‐
rity(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 af‐
ter a reset (or when the server is starting), it reads this file. If this file contains any autho‐
rization 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 connec‐
tions 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 fam‐
ily:name as described in the xhost(1) manual page. There should be no leading or trailing spaces on
any lines. For example:

joesworkstation
corporate.company.com
inet:bigcpu
local:

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.

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. Re‐
strictions 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 security models.

SIGNALS
The X server attaches special meaning to the following signals:

SIGHUP This signal causes the server to close all existing connections, free all resources, and re‐
store all defaults. It is sent by the display manager whenever the main user's main applica‐
tion (usually an xterm or window manager) exits to force the server to clean up and prepare
for the next user.

SIGTERM This signal causes the server to exit cleanly.

SIGUSR1 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 con‐
nection schemes. Xdm uses this feature to recognize when connecting to the server is possi‐
ble.

FONTS
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 /usr/share/fonts/X11/misc,/usr/share/fonts/X11/cyril‐
lic,/usr/share/fonts/X11/100dpi/:unscaled,/usr/share/fonts/X11/75dpi/:un‐
scaled,/usr/share/fonts/X11/Type1,/usr/share/fonts/X11/100dpi,/usr/share/fonts/X11/75dpi,built-ins .

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 de‐
tails.

The font path can be set with the -fp option or by xset(1) after the server has started.

FONTPATH.D
You can specify a special kind of font path in the form catalogue:. The directory specified af‐
ter 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 un‐
derlying 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:

/usr/share/X11/fonts/misc:unscaled,
/usr/share/X11/fonts/75dpi:unscaled,
/usr/share/X11/fonts/Type1,
/usr/share/fonts/default/Type1,
/usr/share/fonts/default/ghostscript

FILES
/etc/Xn.hosts Initial access control list for display number n

/usr/share/fonts/X11/misc,/usr/share/fonts/X11/75dpi,/usr/share/fonts/X11/100dpi
Bitmap font directories

/usr/share/fonts/X11/TTF,/usr/share/fonts/X11/Type1
Outline font directories

/tmp/.X11-unix/Xn Unix domain socket for display number n

/usr/adm/Xnmsgs Error log file for display number n if run from init(8)

/usr/lib/X11/xdm/xdm-errors Default error log file if the server is run from xdm(1)

Manual: Xserver

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