Provided by: xserver-common_21.1.13-2ubuntu1.1_all 
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 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. 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 workstation
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
alternative 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 actually
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 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.
-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 specified
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-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 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
configuration specific.
-extensionextensionName
disables named extension. If an unknown extension name is specified, a list of accepted
extension names is printed.
+extensionextensionName
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).
-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
information 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 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.
+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 default.
-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 application
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 acceleration
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
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.
-maxclients
64|128|256|512 Set the maximum number of clients allowed to connect to the X server. Acceptable
values are 64, 128, 256 or 512.
-render default|mono|gray|color sets the color allocation policy that will be used by the render
extension.
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 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 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 network
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 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.
XKEYBOARD OPTIONS
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
/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
autorepeat-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, XDM-AUTHORIZATION-2, SUN-DES-1, and MIT-KERBEROS-5. See the Xsecurity(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:
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.
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 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 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 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 connection
schemes. Xdm uses this feature to recognize when connecting to the server is possible.
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/cyrillic,/usr/share/fonts/X11/100dpi/:unscaled,/usr/share/fonts/X11/75dpi/:unscaled,/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 details.
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:<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:
/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)
SEE ALSO
General information: X(7)
Protocols: 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
Keyboards: xkeyboard-config(7)
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), Xephyr(1), Xnest(1), Xvfb(1), Xquartz(1), XWin(1).
Server internal documentation: Definition of the Porting Layer for the X v11 Sample Server
AUTHORS
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.