Xserver(1) manual page
Table of Contents
Xserver - X Window System server
X [:displaynumber] [-option
...] [ttyname]
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.
The server is usually started from the X Display Manager program
xdm(1)
. 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(1)
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.
The X server supports connections made using the following
reliable byte-streams:
- TCP/IP
Listen on port 6000+n, where n is the display number. - Unix Domain
- Use /tmp/.X11-unix/Xn
as the filename for the socket, where n is the display number.
- DECnet
Respond to connections to object X$Xn, where n is the display number. This
is not supported in all environments.
All X servers accept the following
command line options:
- -a number
- Set pointer acceleration (i.e. the ratio of
how much is reported to how much the user actually moved the pointer).
The default is 2.
- -ac
- Disable host-based access control mechanisms. Enables
access by any host, and permits any host to modify the access control list.
Use with caution. This option exists primarily for executing remote test
suites.
- -audit level
- Set the audit trail level. The default is 1; only connection
rejections are reported. Level 2 also reports successful connections and
disconnects. Level 0 turns off the audit trail. Audit output is sent on
the standard error output stream.
- -auth authorization-file
- Specify a file
which contains a collection of authorization records used to authenticate
access. See also xdm(1)
- bc
- Disable 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
- Disable backing store support
on all screens.
- -c
- Turn off key-click.
- c volume
- Set key-click volume, range
is 0-100.
- -cc class
- Set the visual class for the root window of color screens.
Class numbers are as specified in the X protocol. Not implemented in all
servers.
- -co filename
- Set name of RGB color database.
- -core
- The server dumps
core on fatal errors.
- -dpi resolution
- Set the resolution of the screen, in
dots per inch. Use when the server cannot determine the screen size from
the hardware. The default is 90.
- -f volume
- Set beep (bell) volume, range is
0-100. The default is 50.
- -fc cursorFont
- Set default cursor font.
- -fn font
- Set
default font.
- -fp fontPath
- Set the font search path. This path is a comma
separated list of directories which the X server uses to search for font
databases.
- -ep encodingPath
- Set the font encoding search path.
- -help
- Print
a usage message.
- -I
- All following command line arguments are ignored.
- -logo
- Turn on the X Window System logo display in the screen-saver. There is currently
no way to change this from a client.
- nologo
- Turn off the X Window System
logo display in the screen-saver. There is currently no way to change this
from a client.
- -p minutes
- Set screen-saver pattern cycle time in minutes.
The default is 10 minutes.
- -pn
- The server is to continue running if it fails
to establish all of its well-known sockets, but establishes at least one.
- -r
- Turn off auto-repeat.
- r
- Turn on auto-repeat.
- -s minutes
- Set screen-saver timeout
time in minutes. The default is 10 minutes.
- -su
- Disable save under support
on all screens.
- -t number
- Set pointer acceleration threshold in pixels (i.e.
after how many pixels pointer acceleration should take effect). The default
is 4.
- -terminate
- The server is to terminate instead of resetting.
- -to seconds
- Set default connection timeout in seconds. The default is 60 seconds.
- -tst
- Disable all testing extensions (e.g., XTEST, XTrap, XTestExtension1).
- ttyxx
- ignored, for servers started the ancient way (from init).
- v
- Set video-off
screen-saver preference.
- -v
- Set video-on screen-saver preference.
- -wm
- Force the
default backing-store of all windows to be WhenMapped; an inexpensive way
of getting backing-store to apply to all windows.
- -x extension
- Load the specified
extension at init. Not supported in most implementations.
You can also have
the X server connect to xdm(1)
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
- Terminate the server after one session.
- -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).
- -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.
The X server implements a simple 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 that held by the server, it is allowed connection
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 the private key. But in many environments, this level
of security is better than the host-based scheme as it provides access control
on a per-user instead of per-host basis.
In addition, the server provides
support for a DES-based authorization scheme, SUN-DES-1, using Sun’s Secure
RPC. It involves encrypting data with the X server’s public key. See the
for more information.
The authorization data is passed to the server in
a private file named with the -auth command line option. Before accepting
connections after a reset or when the server is starting, it reads this
file. If this file contains authorization records, the local host is not
allowed access to the server; only clients which send one of the authorization
records contained in the file in the connection setup information are allowed
access. See the xauth(1)
manual page for a description of the binary format
of this file.
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.
The file contains either an Internet hostname (e.g. expo.lcs.mit.edu) or a
DECnet hostname in double colon format (e.g. hydra::). Each hostname must
be newline separated with no leading or trailing whitespace. For example:
joesworkstation
corporate.company.com
star::
bigcpu::
Users 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.
The X server handles the following signals:
- SIGHUP
- Close
all existing connections, free all resources, and restore server defaults.
This signal is sent by the display manager whenever the user’s primary
application (usually an xterm(1)
or window manager) exits to force the
server to clean up and prepare for the next user.
- SIGTERM
- The server exits
cleanly.
- SIGUSR1
- This signal is used quite differently from either of the
above. When the server starts, determines if SIGUSR1 is set to SIG_IGN.
If this is true 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 the server is ready for client connections (see xdm(1)
).
Fonts
are normally stored as individual files across various 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 (see the -fp),
This path can be overridden using the xset(1)
program.
The default font
path for the X server includes eight directories:
- /usr/openwin/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/openwin/lib/X11/fonts/Speedo
- This directory contains outline
fonts for Bitstream’s Speedo rasterizer. A single font face, contributed
by Bitstream, Inc., in normal, bold, italic, and bold italic, is provided.
- /usr/openwin/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/openwin/lib/X11/fonts/100dpi
- This directory contains 100 dots
per inch versions of some of the fonts in the 75dpi directory.
- /usr/openwin/lib/X11/fonts/F3
- This directory contains scalable outlie fonts for the F3 format. 57 typefaces
are present.
- /usr/openwin/lib/X11/fonts/F3bitmaps
- This directory contains
bitmaps in various point sized for the 57 F3 fonts.
- /usr/openwin/lib/X11/fonts/Xt+
- This directory contains fonts used by OLIT.
- /usr/openwin/lib/X11/fonts/Type1
- This directory contains outline Adobe Type1 fonts.
Font databases are created
by executing the mkfontdir(1)
program in the directory containing the compiled
versions of the fonts (the .pcf files). Whenever fonts are added to a directory,
mkfontdir should be executed so that the server can find the new fonts.
If mkfontdir is not run, the server will not find any fonts in the directory.
Too numerous to list them all. If run from init(1M)
, errors are
typically logged in the file /usr/adm/X*msgs,
- /etc/X*.hosts
- Initial
access control list
- /usr/openwin/lib/X11/fonts/misc
- Bitmap font directory
- /usr/openwin/lib/X11/fonts/75dpi
- Bitmap font directory
- /usr/openwin/lib/X11/fonts/100dpi
- Bitmap font directory
- /usr/openwin/lib/X11/fonts/Speedo
- Outline font directory
- /usr/openwin/lib/X11/fonts/F3
- F3 outline font directory
- /usr/openwin/lib/X11/fonts/F3bitmaps
- Bitmap font directory
- /usr/openwin/lib/X11/fonts/Xt+
- OLIT font directory
- /usr/openwin/lib/X11/fonts/Type1
- Outline font directories
- /usr/openwin/lib/X11/fonts/PEX
- PEX font directories
- /usr/openwin/lib/X11/rgb.txt
- Color database
- /tmp/.X11-unix/X*
- Unix domain socket
- /usr/adm/X*msgs
- Error log file
X11(7)
, bdftopcf(1)
,
mkfontdir(1)
, xauth(1)
, xdm(1)
, xhost(1)
, xinit(1)
, xset(1)
, xsetroot(1)
,
xterm(1)
, Xsun(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
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 1984, 1985, 1986, 1987, 1988,
1989, 1990, 1991 Massachusetts Institute of Technology.
See X11(7)
for a full statement of rights and permissions.
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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