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.  In INTER­ACTIVE X11 Releases 1.1 and later, X is a link to the program xfront(1), which automatically executes the appropriate server. 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

The INTER­ACTIVE X11 release supports:

Xcpqag COMPAQ AG1024 smart board interface server
XcvcCornerstone smart board interface server
Xdcaga Desktop Computing AGA1024 smart board interface server
Xgp8514/A graphics processor smart board interface server
XhrcHercules monochrome smart board interface server
XigspIMAgraph TI1210 smart board interface server
XlvpLaserView PLUS smart board interface server
Xmsfdp MegaScan FDP-6120 smart board interface server
XnnpNumber Nine PEPPER PRO1280 smart board interface server
XnnpiNumber Nine PEPPER PRO1024ISA smart board interface server
XpwPixelworks smart board interface server
Xrren2 Renaissance Rendition II smart board interface server
Xsp200 Spectre SP200 smart board interface server
XtisdbTexas Instruments TMS34010 smart board interface server
Xv256256 color VGA smart board interface server
XvgaEGA/VGA color smart board interface server
Xviking Moniterm 21/91 Viking smart board interface server
XwgeBell Technologies Workstation Graphics Engine (Blit) server

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 user names 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 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 in to 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 System Domain
The sample server uses /tmp/.X11-unix/Xn as the file name for a STREAMS pipe node, 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).

−bs Disables backing store support on all screens. 

−c Turns off key-click. 

−config filename
Specifies configuration file to use instead of /usr/lib/X11/Xconfig. 

c volume Sets key-click volume (allowable range: 0-8). 

−f volume
Sets beep (bell) volume (allowable range: 0-7).

−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 screensaver timeout in seconds.

v Sets video-on screen-saver preference. 

−v Sets video-off screen-saver preference. 

−co filename
Sets name of rgb color database. 

−help Prints a usage message. 

−fp fontPath
Sets the search path for fonts.

−fc cursorFont
Sets the default cursor font.

−fn font
Sets the default font.

−wm Forces the default backing-store of all windows to be WhenMapped; an easy way of getting backing-store to apply to all windows. 

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

SECURITY

The sample server uses an 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.  The core protocol does have support for providing authentication information when establishing connections, but is not used in the sample implementation.  Sites that have 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. 

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 principal 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 dot-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(1M), 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 System domain socket

/usr/adm/X*msgs error log file

SEE ALSO

X(1), Xcpqag(1), Xcvc(1), Xdcaga(1), Xgp(1), Xhrc(1), Xigsp(1), Xlvp(1), Xmsfdp(1), Xnnp(1), Xnnpi(1), Xpw(1), Xrren2(1) Xsp200(1), Xtisdb(1), Xv256(1), Xvga(1), Xviking(1), Xwge(1), mkfontdir(1), uwm(1), xdm(1), xfront(1), xhost(1), xinit(1), xset(1), xsetroot(1), xterm(1). 
init(1M) in the INTERACTIVE UNIX System User’s/System Administrator’s Reference Manual. 
inittab(4) in the INTERACTIVE SDS Guide and Programmer’s Reference Manual. 
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.  Users 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 thousands.  Also see the file /doc/contributors in the sample distribution for a more complete list. 

\*U  —  Version 1.0