XSERVER(1) RISC/os Reference Manual XSERVER(1)
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:
Xqvss Digital monochrome vaxstationII or II
Xqdss Digital color vaxstationII or II
Xsun Sun monochrome or color Sun 2, 3, or 4
Xibm IBM AED, APA and megapel PC/RT, 8514 and VGA PS/2 model 80
Xapollo Apollo monochrome or color (Domain/OS SR10.1 or SR10.2)
Xhp HP Topcat 9000s300
XmacII Apple monochrome Macintosh II
Xcfbpmax Digital color DECstation 3100
Xmfbpmax Digital monochrome DECstation 3100
Xtek Tektronix 4319 (this is the only tested configuration)
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 is no longer included.
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 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
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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. This is not supported in all
environments.
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.
-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.
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-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. This path is a
comma separated list of directories which the sample
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. 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 sys-
tems.
-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 sys-
tems.
-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.
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-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).
-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 sup-
ported in most implementations.
You can also have the X server connect to xdm 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 servers as a sample implementa-
tion of the server side of XDMCP. For more information on
this protocol, see the XDMCP specification in
docs/XDMCP/xdmcp.ms. 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.
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-once Normally, the server keeps starting sessions, one
after the other. This option makes the server exit
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'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.
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 pro-
tocol, MIT-MAGIC-COOKIE-1 which uses data private to author-
ized 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), 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.
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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 con-
sists 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 for-
mat (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.
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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 when-
ever 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
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 it's 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 list of directories in which the server looks when try-
ing 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 the fonts in the
75dpi directory for 100 dots per inch displays.
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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/100dpi
/usr/lib/X11/fonts/misc, /usr/lib/X11/fonts/75dpi,
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 Sam-
ple 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 denom-
inator 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.
COPYRIGHT
Copyright 1984, 1985, 1986, 1987, 1988, 1989, Massachusetts
Institute of Technology.
See X(1) for a full statement of rights and permissions.
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AUTHORS
The sample server was originally written by Susan Ange-
branndt, 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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