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 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.
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.
-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).
-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 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
causes the server to terminate at server reset, instead of
continuing to run. This overrides a previous -noreset command
line option.
-to seconds
sets default connection timeout in seconds.
-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.
-wm 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.
-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), 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
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.
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