XSERVER(1) X11 5.4R3.00 XSERVER(1)
NAME
Xserver - X Window System server
SYNOPSIS
X [:displaynumber] [-option ...] [ttyname]
DESCRIPTION
X is the generic name for the X Window System 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 server is usually started from the X Display Manager program xdm.
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. It is easily configured for sites
that wish to provide nice, consistent interfaces for novice users
(loading convenient sets of resources, starting up a window manager,
clock, and nice selection of terminal emulator windows).
Installations that run more than one window system will still need to
use the xinit utility. 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 xdm, or build other
interfaces for novice users.
When the X server starts up, it takes over the display. If you are
running on a workstation whose console is the display, you cannot log
into the console while the server is running.
NETWORK CONNECTIONS
The X server supports connections made using the following reliable
byte-streams:
TCPIP
The server listens on port 6000+n, where n is the display number.
Unix Domain
The X server uses /tmp/.X11-unix/Xn as the filename for the
socket, where n is the display number.
DECnet
The server responds to connections to object X$Xn, where n is the
display number. This is not supported in all environments.
OPTIONS
All of the X servers accept the following command line options:
-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
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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 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 and
Xsecurity manual pages.
bc disables certain kinds of error checking, for bug
compatibility with previous releases (e.g., to work around
bugs in R2 and R3 xterms and toolkits). Deprecated.
-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.
-co filename
sets name of RGB color database.
-core causes the server to generate a core dump on fatal errors.
-dpi resolution
sets the resolution of the screen, in dots per inch. To be
used when the server cannot determine the screen size from
the hardware.
-f volume
sets feep (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.
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-help prints a usage message.
-I causes all remaining command line arguments to be ignored.
-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. This option is not available in all
operating systems.
-lf files
sets the number-of-open-files limit of the server to the
specified number. A value is zero makes the limit as large
as possible. The default value of -1 leaves the limit
unchanged. This option is not available in all operating
systems.
-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. This option is not available in all
operating systems.
-logo turns on the X Window System logo display in the screen-
saver. There is currently no way to change this from a
client.
nologo turns off the X Window System logo display in the screen-
saver. There is currently no way to change this from a
client.
-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, but establishes at
least one.
-r turns off auto-repeat.
r turns on auto-repeat.
-s minutes
sets screen-saver timeout time in minutes.
-su disables save under support on all screens.
-t number
sets pointer acceleration threshold in pixels (i.e. after how
many pixels pointer acceleration should take effect).
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-terminate
causes the server to terminate at server reset, instead of
continuing to run.
-to seconds
sets default connection timeout in seconds.
-tst disables all testing extensions (e.g., XTEST, XTrap,
XTestExtension1).
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; a cheap trick way of getting backing-store to
apply to all windows.
-x extension
loads the specified extension at init. Not supported in most
implementations.
You can also have the X server connect to xdm using XDMCP. Although
this is not typically useful as it does not allow xdm to manage the
server process, it can be used to debug XDMCP implementations, and
serves as a sample implementation of the server side of XDMCP. For
more information on this protocol, see the X Display Manager Control
Protocol specification. The following options control the behavior
of XDMCP.
-query host-name
Enable XDMCP and send Query packets to the specified host.
-broadcast
Enable XDMCP and broadcast BroadcastQuery packets to the
network. The first responding display manager will be chosen
for the session.
-indirect host-name
Enable XDMCP and send IndirectQuery packets to the specified
host.
-port port-num
Use an alternate port number for XDMCP packets. Must be
specified before any -query, -broadcast or -indirect options.
-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).
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-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.
Many servers also have device-specific command line options. See the
manual pages for the individual servers for more details.
SECURITY
The X server implements a simplistic authorization protocol, MIT-
MAGIC-COOKIE-1 which uses data private to authorized clients and the
server. This is a rather trivial scheme; if the client passes
authorization data which is the same as the server has, it is allowed
access. This scheme is worse than the host-based access control
mechanisms in environments with unsecure networks as it allows any
host to connect, given that it has discovered the private key. But
in many environments, this level of security is better than the host-
based scheme as it allows access control per-user instead of per-
host.
In addition, the server provides support for a DES-based
authorization scheme, XDM-AUTHORIZATION-1, which is more secure
(given a secure key distribution mechanism). This authorization
scheme can be used in conjunction with XDMCP's authentication scheme
(XDM-AUTHENTICATION-1) or in isolation.
The authorization data 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. Maintenance of this
file, and distribution of its contents to remote sites for use there
is left as an exercise for the reader.
The server also provides support for SUN-DES-1, using Sun's Secure
RPC. It involves encrypting data with the X server's public key.
See the Xsecurity manual page for more information.
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
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either an Internet hostname (e.g. expo.lcs.mit.edu) or a DECnet
hostname in double colon format (e.g. hydra::). There should be no
leading or trailing spaces on any lines. For example:
joesworkstation
corporate.company.com
star::
bigcpu::
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. Sites that have better authentication and authorization
systems (such as Kerberos) 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
Fonts are usually stored as individual files in directories. 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. Although most
sites will choose to have the X server start up with the appropriate
font path (using the -fp option mentioned above), it can be
overridden using the xset program.
The default font path for the X server contains four directories:
/usr/lib/X11/fonts/misc
This directory contains many miscellaneous bitmap fonts that
are useful on all systems. It contains a family of fixed-
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width fonts, a family of fixed-width fonts from Dale
Schumacher, several Kana fonts from Sony Corporation, two JIS
Kanji fonts, two Hangul fonts from Daewoo Electronics, two
Hebrew fonts from Joseph Friedman, the standard cursor font,
two cursor fonts from Digital Equipment Corporation, and
cursor and glyph fonts from Sun Microsystems. It also has
various font name aliases for the fonts, including fixed and
variable.
/usr/lib/X11/fonts/Speedo
This directory contains outline fonts for Bitstream's Speedo
rasterizer. A single font face, in normal, bold, italic, and
bold italic, is provided, contributed by Bitstream, Inc.
/usr/lib/X11/fonts/75dpi
This directory contains bitmap fonts contributed by Adobe
Systems, Inc., Digital Equipment Corporation, Bitstream,
Inc., Bigelow and Holmes, and Sun Microsystems, Inc. for 75
dots per inch displays. An integrated selection of sizes,
styles, and weights are provided for each family.
/usr/lib/X11/fonts/100dpi
This directory contains 100 dots per inch versions of some of
the fonts in the 75dpi directory.
Font databases are created by running the mkfontdir program in the
directory containing the compiled versions of the fonts (the .pcf
files). Whenever fonts are added to a directory, mkfontdir should be
rerun so that the server can find the new fonts. If mkfontdir is not
run, the server will not be able to find any fonts in the directory.
DIAGNOSTICS
Too numerous to list them all. If run from init(8), errors are
typically logged in the file /usr/adm/X*msgs,
FILES
/etc/X*.hosts Initial access control list
/usr/lib/X11/fonts/misc, /usr/lib/X11/fonts/75dpi,
/usr/lib/X11/fonts/100dpi
Bitmap font directories
/usr/lib/X11/fonts/Speedo Outline font directories
/usr/lib/X11/fonts/PEX PEX font directories
/usr/lib/X11/rgb.txt Color database
/tmp/.X11-unix/X* Unix domain socket
/usr/adm/X*msgs Error log file
SEE ALSO
X(1), bdftopcf(1), mkfontdir(1), fs(1), xauth(1), xdm(1), xhost(1),
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xinit(1), xset(1), xsetroot(1), xterm(1), Xdec(1), Xibm(1),
XmacII(1), Xmips(1), Xqdss(1), Xqvss(1), Xsun(1), Xtek(1), X386(1) X
Window System Protocol, Definition of the Porting Layer for the X v11
Sample Server, Strategies for Porting the X v11 Sample Server,
Godzilla's Guide to Porting the X V11 Sample Server
BUGS
The option syntax is inconsistent with itself and xset(1).
The acceleration option should take a numerator and a denominator
like the protocol.
If X dies before its clients, new clients won't be able to connect
until all existing connections have their TCP TIME_WAIT timers
expire.
The color database is missing a large number of colors.
COPYRIGHT
Copyright 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991
Massachusetts Institute of Technology.
See X(1) for a full statement of rights and permissions.
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.
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