XSERVER(1) 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 emu-
lator 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 dis-
play 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
X Version 11 Release 5 1
XSERVER(1) XSERVER(1)
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 control list. Use with
extreme caution. This option exists primarily for
running test suites remotely.
-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 toolk-
its). 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.
-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
X Version 11 Release 5 2
XSERVER(1) XSERVER(1)
comma separated list of directories which the X
server searches for font databases.
-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.
-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
X Version 11 Release 5 3
XSERVER(1) XSERVER(1)
should take effect).
-to seconds
sets default connection timeout in seconds.
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 back-
ing-store to apply to all windows.
-x extension
loads the specified extension at init. Not sup-
ported 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 implementa-
tion 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 speci-
fied host.
-broadcast
Enable XDMCP and broadcast BroadcastQuery packets
to the network. The first responding display man-
ager 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.
-once Normally, the server keeps starting sessions, one
after the other. This option makes the server
exit after the first session is over.
-class display-class
XDMCP has an additional display qualifier used in
resource lookup for display-specific options.
X Version 11 Release 5 4
XSERVER(1) XSERVER(1)
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.
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 proto-
col, MIT-MAGIC-COOKIE-1 which uses data private to autho-
rized 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 mecha-
nisms in environments with unsecure networks as it allows
any host to connect, given that it has discovered the pri-
vate key. But in many environments, this level of secu-
rity 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 pri-
vate 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
X Version 11 Release 5 5
XSERVER(1) XSERVER(1)
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 authoriza-
tion 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 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 dis-
play, it has full run of the screen. Sites that have bet-
ter authentication and authorization systems (such as Ker-
beros) 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 exist-
ing 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
X Version 11 Release 5 6
XSERVER(1) XSERVER(1)
the server is possible.
FONTS
Fonts are usually stored as individual files in directo-
ries. 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-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 Equip-
ment Corporation, and cursor and glyph fonts from
Sun Microsystems. It also has various font name
aliases for the fonts, including fixed and vari-
able.
/usr/lib/X11/fonts/Speedo
This directory contains outline fonts for Bit-
stream's Speedo rasterizer. A single font face,
in normal, bold, italic, and bold italic, is pro-
vided, contributed by Bitstream, Inc.
/usr/lib/X11/fonts/75dpi
This directory contains bitmap fonts contributed
by Adobe Systems, Inc., Digital Equipment Corpora-
tion, 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 pro-
gram 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 direc-
tory.
X Version 11 Release 5 7
XSERVER(1) XSERVER(1)
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), 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, Defi-
nition 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 Ange-
branndt, Raymond Drewry, Philip Karlton, and Todd Newman,
from Digital Equipment Corporation, with support from a
large cast. It has since been extensively rewritten by
X Version 11 Release 5 8
XSERVER(1) XSERVER(1)
Keith Packard and Bob Scheifler, from MIT.
X Version 11 Release 5 9