.\"$SCCSID( @(#)Xserver.man	1.1 AIX ) Modified: 16:26:14 7/17/92 
.TH XSERVER 1 "Release 5"  "X Version 11"
.SH NAME
Xserver \- X Window System server
.SH SYNOPSIS
.B X
[:displaynumber] [\-option ...] [ttyname]
.SH DESCRIPTION
.I X
is the generic name for the X Window System server.  It is frequently a link
or a copy of the appropriate server binary for driving the most frequently
used server on a given machine.
.SH "STARTING THE SERVER"
The server is usually started from the X Display Manager program \fIxdm\fP.
This utility is run from the system boot files and takes care of keeping
the server running, prompting for usernames and passwords, and starting up
the user sessions.  It is easily configured for sites that wish to provide
nice, consistent interfaces for novice users (loading convenient sets of
resources, starting up a window manager, clock, and nice selection of 
terminal emulator windows).
.PP
Installations that run more than one window system will still need to use the
\fIxinit\fP utility.  However, \fIxinit\fP is to be considered a tool for
building startup scripts and is not intended for use by end users.  Site
administrators are \fBstrongly\fP urged to use \fIxdm\fP,
or build other interfaces for novice users.
.PP
When the X server starts up, it takes over the display.  If you 
are running on a workstation whose console is the display, you cannot log into
the console while the server is running.
.SH "NETWORK CONNECTIONS"
The X server supports connections made using the following reliable
byte-streams:
.TP 4
.I TCP\/IP
.br
The server listens on port 6000+\fIn\fP, where \fIn\fP is the display number.
.TP 4
.I "Unix Domain"
The X server uses \fI/tmp/.X11-unix/X\fBn\fR as the filename for 
the socket, where \fIn\fP is the display number.
.TP 4
.I "DECnet"
.br
The server responds to connections to object \fIX$X\fBn\fR, where \fIn\fP
is the display number.  This is not supported in all environments.
.SH OPTIONS
All of the X servers accept the following command line options:
.TP 8
.B \-a \fInumber\fP
sets pointer acceleration (i.e. the ratio of how much is reported to how much
the user actually moved the pointer).
.TP 8
.B \-auth \fIauthorization-file\fP
Specifies a file which contains a collection of authorization records used
to authenticate access.  See also the \fIxdm\fP and \fIXsecurity\fP manual
pages.
.TP 8
.B 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.
.TP 8
.B \-bs
disables backing store support on all screens.
.TP 8
.B \-c
turns off key-click.
.TP 8
.B c \fIvolume\fP
sets key-click volume (allowable range: 0-100).
.TP 8
.B \-cc \fIclass\fP
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.
.TP 8
.B \-co \fIfilename\fP
sets name of RGB color database.
.TP 8
.B \-dpi \fIresolution\fP
sets the resolution of the screen, in dots per inch.
To be used when the server cannot determine the screen size from the hardware.
.TP 8
.B \-f \fIvolume\fP
sets feep (bell) volume (allowable range: 0-100).
.TP 8
.B \-fc \fIcursorFont\fP
sets default cursor font.
.TP 8
.B \-fn \fIfont\fP
sets the default font.
.TP 8
.B \-fp \fIfontPath\fP
sets the search path for fonts.  This path is a comma separated list of
directories which the X server searches for font databases.
.TP 8
.B \-help
prints a usage message.
.TP 8
.B \-I
causes all remaining command line arguments to be ignored.
.TP 8
.B \-ld \fIkilobytes\fP
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.
.TP 8
.B \-lf \fIfiles\fP
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.
.TP 8
.B \-ls \fIkilobytes\fP
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.
.TP 8
.B \-logo
turns on the X Window System logo display in the screen-saver.
There is currently no way to change this from a client.
.TP 8
.B nologo
turns off the X Window System logo display in the screen-saver.
There is currently no way to change this from a client.
.TP 8
.B \-p \fIminutes\fP
sets screen-saver pattern cycle time in minutes.
.TP 8
.B \-r
turns off auto-repeat.
.TP 8
.B r
turns on auto-repeat.
.TP 8
.B \-s \fIminutes\fP
sets screen-saver timeout time in minutes.
.TP 8
.B \-su
disables save under support on all screens.
.TP 8
.B \-t \fInumber\fP
sets pointer acceleration threshold in pixels (i.e. after how many pixels
pointer acceleration should take effect).
.TP 8
.B \-to \fIseconds\fP
sets default connection timeout in seconds.
.TP 8
.B tty\fIxx\fP
ignored, for servers started the ancient way (from init).
.TP 8
.B v
sets video-off screen-saver preference.
.TP 8
.B \-v
sets video-on screen-saver preference.
.TP 8
.B \-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.
.TP 8
.B \-x \fIextension\fP
loads the specified extension at init.
Not supported in most implementations.
.PP
You can also have the X server connect to \fIxdm\fP using XDMCP.
Although this is not typically useful as it does not allow \fIxdm\fP
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 \fIX Display Manager Control Protocol\fP specification.
The following options control the behavior of XDMCP.
.TP 8
.B \-query \fIhost-name\fP
Enable XDMCP and send Query packets to the specified host.
.TP 8
.B \-broadcast
Enable XDMCP and broadcast BroadcastQuery packets to the network.  The
first responding display manager will be chosen for the session.
.TP 8
.B \-indirect \fIhost-name\fP
Enable XDMCP and send IndirectQuery packets to the specified host.
.TP 8
.B \-port \fIport-num\fP
Use an alternate port number for XDMCP packets.  Must be specified before
any \-query, \-broadcast or \-indirect options.
.TP 8
.B \-once
Normally, the server keeps starting sessions, one after the other.  This
option makes the server exit after the first session is over.
.TP 8
.B \-class \fIdisplay-class\fP
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).
.TP 8
.B \-cookie \fIxdm-auth-bits\fP
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!).
.TP 8
.B \-displayID \fIdisplay-id\fP
Yet another XDMCP specific value, this one allows the display manager to
identify each display so that it can locate the shared key.
.PP
Many servers also have device-specific command line options.  See the
manual pages for the individual servers for more details.
.SH SECURITY
.PP
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.
.PP
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.
.PP
The authorization data is passed to the server in a private file named with
the \fB\-auth\fP 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 \fIXau\fP
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.
.PP
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 \fIXsecurity\fP manual page for more information.
.PP
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 \fI/etc/X\fBn\fI.hosts\fR, where
\fBn\fP 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:
.sp
.in +8
.nf 
joesworkstation
corporate.company.com
star::
bigcpu::
.fi
.in -8
.PP
Users can add or remove hosts from this list and enable or disable access
control using the \fIxhost\fP command from the same machine as the server.
.PP
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.
.SH SIGNALS
The X server attaches special meaning to the following signals:
.TP 8
.I 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 \fIxterm\fP or window
manager) exits to force the server to clean up and prepare for the next
user.
.TP 8
.I SIGTERM
This signal causes the server to exit cleanly.
.TP 8
.I 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.
\fIXdm\fP uses this feature to recognize when connecting to the server
is possible.
.SH 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 \fIfont path\fP.  Although most sites will choose to have the X server
start up with the appropriate font path (using the \fI\-fp\fP option mentioned
above), it can be overridden using the \fIxset\fP program.
.PP
The default font path for the X server contains four directories:
.TP 8
.I /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
\fBfixed\fP and \fBvariable\fP.
.TP 8
.I /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.
.TP 8
.I /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.
.TP 8
.I /usr/lib/X11/fonts/100dpi
This directory contains 100 dots per inch versions of some of the fonts in the 
\fI75dpi\fP directory.  
.PP
Font databases are created by running the \fImkfontdir\fP program in the
directory containing the compiled versions of the fonts (the \fI.pcf\fP files).
Whenever fonts are added to a directory, \fImkfontdir\fP should be rerun
so that the server can find the new fonts.  \fBIf \fImkfontdir\fP is not
run, the server will not be able to find any fonts in the directory.\fR
.SH DIAGNOSTICS
Too numerous to list them all.
If run from \fIinit(8)\fP, errors are typically logged
in the file \fI/usr/adm/X*msgs\fP,
.SH FILES
.TP 30
/etc/X*.hosts
Initial access control list
.TP 30
/usr/lib/X11/fonts/misc, /usr/lib/X11/fonts/75dpi, /usr/lib/X11/fonts/100dpi 
Bitmap font directories
.TP 30
/usr/lib/X11/fonts/Speedo
Outline font directories
.TP 30
/usr/lib/X11/fonts/PEX
PEX font directories
.TP 30
/usr/lib/X11/rgb.txt
Color database
.TP 30
/tmp/.X11-unix/X*
Unix domain socket
.TP 30
/usr/adm/X*msgs
Error log file
.SH "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)
.I "X Window System Protocol,"
.I "Definition of the Porting Layer for the X v11 Sample Server,"
.I "Strategies for Porting the X v11 Sample Server,"
.I "Godzilla's Guide to Porting the X V11 Sample Server"
.SH BUGS
The option syntax is inconsistent with itself and \fIxset(1)\fP.
.PP
The acceleration option should take a numerator and a denominator like the
protocol.
.PP
If
.I X
dies before its clients, new clients won't be able to connect until all
existing connections have their TCP TIME_WAIT timers expire.
.PP
The color database is missing a large number of colors.
.PP
.SH COPYRIGHT
Copyright 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991
Massachusetts Institute of Technology.
.br
See \fIX(1)\fP for a full statement of rights and permissions.
.SH 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.