X Server
Table of Contents
X :displaynumber [-option] ttyname
"X" is the generic name for the window system server. It is started
by the dtlogin(1X) program which is typically run by
init(1M). Alternatively it may be started from the xinit(1)
program, which is called by x11start. The displaynumber
argument is used by clients in their DISPLAY environment variables to
indicate which server to contact (machines may have several displays
attached). This number can be any number. If no number is specified, 0 is
used. This number is also used in determining the names of various startup
files. The ttyname argument is passed in by init and isn't
used.
The Hewlett-Packard server has support for the following protocols:
- TCP/IP
- The server listens on port 6000+n, where n is the display
number.
- Local Socket IPC Mechanism
- The file name for the socket is "/usr/spool/sockets/X11/*" where
"*" is the display number.
- Shared Memory IPC
- This is the default connection that the X Library will use to connect to
an X server on the same machine if the DISPLAY environment
variable is set to "local:*" or ":*" where "*"
is the number of the display.
When the 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 following options can be given on the command line to the X server.
- -a number
- Sets pointer acceleration (i.e. the ratio of how much is reported to how
much the user actually moved the pointer).
- -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.
- 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).
- -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 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 server searches for font databases.
- -help
- Prints a usage message.
- -I
- Causes all remaining command line arguments to be ignored.
- -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
- Allows X server to run even if one or more communications mechanisms fails
to initialize.
- -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 keyboard auto-repeat.
- r
- Turns on keyboard 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).
- -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).
- -terminate
- Causes server to terminate when all clients disconnect.
- v
- Sets video-on screen-saver preference. A window that changes regularly
will be used to save the screen.
- -v
- Sets video-off screen-saver preference. The screen will be blanked to
save the screen.
- -wm
- Forces the default backing-store of all windows to be WhenMapped;
a less-expensive way of getting backing-store to apply to all windows.
You can also have the X server connect to xdm(1) or
dtlogin(1X) using XDMCP. Although this is not typically useful as
it doesn't 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. 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. Default port number is 177.
- -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's very private, being on the command line and
all...).
- -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.
Though X will usually be run by dtlogin from init, it is
possible to run X directly from init. For information about running
X from dtlogin, see the dtlogin man page.
To run X directly from init, it is necessary to modify
/etc/inittab and /etc/gettydefs. Detailed information on
these files may be obtained from the inittab(4) and
gettydefs(4) man pages.
To run X from init on display 0, with a login xterm running
on /dev/ttypf, in init state 3, the following line must be
added to /etc/inittab:
X0:3:respawn:env PATH=/bin:/usr/bin/X11:/usr/bin xinit -L ttyqf -- :0
To run X with a login hpterm, the following should be used instead:
X0:3:respawn:env PATH=/bin:/usr/bin/X11:/usr/bin xinit hpterm =+1+1 -n login -L ttyqf -- :0
In addition, the following line must be added to /etc/gettydefs (this
should be a single line):
Xwindow# B9600 HUPCL PARENB CS7 # B9600 SANE PARENB CS7 ISTRIP IXANY TAB3 #X login: #Xwindow
There should not be a getty running against the display whenever X is
run from xinit.
The sample 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 inferior to 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), but as DES is not generally distributable, the
implementation is missing routines to encrypt and decrypt the authorization
data. 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 sample server also uses a host-based access control list for deciding
whether or not to accept connections from clients on a particular machine.
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 an Internet hostname
(e.g., expo.lcs.mit.edu). There should be no leading or trailing
spaces on any lines. For example:
joesworkstation
corporate.company.com
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.
For example:
$ xhost +janesworkstation
janesworkstation being added to access control list
$ xhost +
all hosts being allowed (access control disabled)
$ xhost -
all hosts being restricted (access control enabled)
$ xhost
access control enabled (only the following hosts are allowed)
joesworkstation
janesworkstation
corporate.company.com
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 (xdm or dtlogin) whenever the main user's main application 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 are usually stored as individual files in directories. The list of
directories in which the server looks when trying to open a font is controlled
by the font path. Although most sites will choose to have the server start up
with the appropriate font path (using the -fp option mentioned
above), it can be overridden using the xset program.
Font databases are created by running the mkfontdir or
stmkdirs program in the directory containing the compiled versions of
the fonts (mkfontdir) or font outlines (stmkdirs.) Whenever
fonts are added to a directory, mkfontdir or stmkdirs should
be rerun so that the server can find the new fonts. If mkfontdir or
stmkdirs is not run, the server will not be able to find any of the
new fonts in the directory.
In addition, the X server supports font servers. A font server is a networked
program that supplies fonts to X servers and other capable programs. In order
to communicate with a font server, the font servers address must be supplied
as part of the X server's font path. A font server's address is specified
as:
transport/hostname:port-number
where transport is always "tcp", hostname is the
hostname of the machine being connected to (no hostname means a local
connection) and port-number is the tcp address that the font server is
listening at (typically 7000.)
Too numerous to list them all. If run from init(1M), errors are
logged in the file /usr/adm/X*msgs.
- /etc/inittab
- Script for the init process
- /etc/gettydefs
- Speed and terminal settings used by getty
- /etc/X*.hosts
- Initial access control list
- /usr/lib/X11/fonts
- Top level font directory
- /usr/lib/X11/rgb.txt
- Color database
- /usr/lib/X11/rgb.pag
- Color database
- /usr/lib/X11/rgb.dir
- Color database
- /usr/spool/sockets/X11/*
- IPC mechanism socket
- /usr/adm/X*msgs
- Error log file
- /usr/lib/X11/X*devices
- Input devices used by the server. This file contains many example
configurations.
- /usr/lib/X11/X*screens
- Screens used by the server. This file contains many example
configurations.
- /usr/lib/X11/X*pointerkeys
- Keyboard pointer device file. This file contains many example
configurations.
- /usr/lib/X11/XHPkeymaps
- Key device database used by the X server.
The option syntax is inconsistent with itself and xset(1). The
acceleration option should take a numerator and a denominator like the
protocol. The color database is missing a large number of colors. However,
there doesn't seem to be a better one available that can generate RGB values.
Copyright 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992 Massachusetts
Institute of Technology.
Copyright 1992 Hewlett Packard Company.
See X(1) for a full statement of rights and
permissions.
MIT Distribution.
dtlogin(1X), bdftopcf(1), fs(1),
getty(1M), gettydefs(4), gwindstop(1),
hpterm(1), init(1M), inittab(4),
mkfontdir(1), rgb(1), stmkdirs(1),
x11start(1), xclock(1), xfd(1), xhost(1),
xinit(1), xinitcolormap(1), xload(1),
xmodmap(1), xrefresh(1), xseethru(1),
xset(1), xsetroot(1), xterm(1),
xwcreate(1), xwd(1), xwdestroy(1),
xwininfo(1), xwud(1).