NAME

X - 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.  The sample server from MIT supports the following platforms:

XqvssDigital monochrome vaxstationII or II
XqdssDigital color vaxstationII or II
XsunSun monochrome or color Sun 2, 3, or 4
XhpHP Topcat 9000s300
XapolloApollo monochrome (Domain/IX 9.6)
XibmIBM APA and megapel PC/RT
XmacIIApple monochrome Macintosh II
XplxParallax color and video graphics controller

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). 

Since xdm now handles automatic starting of the server in a portable way, the -L option to xterm is now considered obsolete.  Support for starting a login window from 4.3bsd-derived /etc/ttys files may not be included in future releases. 

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 adminstrators are strongly urged to build nicer interfaces for novice users. 

When the sample 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 sample server supports connections made using the following reliable byte-streams:

TCP/IP
The server listens on port htons(6000+n), where n is the display number. 

Unix Domain
The sample 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. 

OPTIONS

All of the sample 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).

−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). 

-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.

−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.

−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. The default value is zero, making the data size as large as possible.  A value of -1 leaves the data space 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. The default value is zero, making the stack size as large as possible.  A 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 numbers
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-on screen-saver preference. 

−v sets video-off 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.

Many servers also have device-specific command line options.  See the manual pages for the individual servers for more details. 

SECURITY

The sample server implements a simplistic authorization protocol which uses data private to authorized clients and the server.  The authorzation data is passed to the server in a private file named with the -auth command line option.  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.  The authorization name supported is "MIT-MAGIC-COOKIE-1".  See the Xau manual page for a description of the binary format of this file.  Maintenence 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 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.  For example:

%  xhost +janesworkstation
janesworkstation being added to access control list
%  xhost -star::
public:: being removed from 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
bigcpu::

Unlike some window systems, X 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 sample 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.

FONTS

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. 

The default font path for the sample server contains three directories:

/usr/lib/X11/fonts/misc
This directory contains several miscellaneous fonts that are useful on all systems.  It contains a very small family of fixed-width fonts (6x10, 6x12, 6x13, 8x13, 8x13bold, and 9x15) and the cursor font.  It also has font name aliases for the commonly used fonts fixed and variable. 

/usr/lib/X11/fonts/75dpi
This directory contains fonts contributed by Adobe Systems, Inc. and Digital Equipment Corporation and by Bitstream, 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 versions of some of the fonts in the 75dpi directory for 100 dots per inch displays. 

Font databases are created by running the mkfontdir program in the directory containing the compiled versions of the fonts (the .snf 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 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
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), xdm(1), mkfontdir(1), xinit(1), xterm(1), twm(1), xhost(1), xset(1), xsetroot(1), ttys(5), init(8), Xqdss(1), Xqvss(1), Xsun(1), Xapollo(1), XmacII(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.  However, there doesn’t seem to be a better one available that can generate RGB values tailorable to particular displays. 

The xterm -L method for starting an initial window from /etc/ttys is completely inadequate and should be removed.  People should use xdm instead. 

COPYRIGHT

Copyright 1984, 1985, 1986, 1987, 1988, 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, with support from a cast of thouands.  See also the file doc/contributors in the sample distribution for a more complete list. 

NEWS-OSRelease 3.3