XSERVER(1)

NAME

X - X Window System server

SYNOPSIS

X :displaynumber [-option] ttyname

DESCRIPTION

X is the window system server. It is started by the vuelogin(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 (large 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 htons(6000+N), where N is the display number.

Local IPC Mechanism
The file name for the socket is /usr/spool/sockets/X11/* where "*" is the display number.

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.

OPTIONS

The following options can be given on the command line to any 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).

−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.

−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 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 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 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 supported in most implementations.

You can also have the X server connect to xdm(1) or vuelogin(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 servers as a sample implementation 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. Default port number is 177.

−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.

RUNNING FROM INIT

Though X will usually be run by vuelogin from init, it is possible to run X directly from init. From information about running X from vuelogin, see the vuelogin 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 for states in which X is run from xinit.

SECURITY

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 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. 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 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

X will catch the SIGHUP signal sent by init(1M) after the initial process (usually the login terminal window) started on the display terminates. This signal causes all connections to be closed (thereby “disowning” the terminal), all resources to be freed, and all defaults restored.

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.

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(1M), errors are logged in the file /usr/adm/X*msgs,

FILES

/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 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

/usr/lib/X11/X*screens Screens used by the server

/usr/lib/X11/X*pointerkeys Keyboard pointer device file

NOTES

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.

COPYRIGHT

ORIGIN

MIT Distribution

Museum

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