XSERVER(1) X Version 11 (Release 5) 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:
TCP/IP
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
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XSERVER(1) X Version 11 (Release 5) XSERVER(1)
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 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 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.
-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.
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XSERVER(1) X Version 11 (Release 5) XSERVER(1)
-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.
-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.
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XSERVER(1) X Version 11 (Release 5) XSERVER(1)
-t number
sets pointer acceleration threshold in pixels (i.e.
after how many pixels pointer acceleration 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
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.
-once Normally, the server keeps starting sessions, one
after the other. This option makes the server exit
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XSERVER(1) X Version 11 (Release 5) XSERVER(1)
after the first session is over.
-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.
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
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XSERVER(1) X Version 11 (Release 5) XSERVER(1)
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
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
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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-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.
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XSERVER(1) X Version 11 (Release 5) XSERVER(1)
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/100dpi
/usr/lib/X11/fonts/misc, /usr/lib/X11/fonts/75dpi,
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, 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.
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XSERVER(1) X Version 11 (Release 5) XSERVER(1)
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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