:displaynumber the X server runs as the given displaynumber, which by default is 0. If multiple X servers are to run simultaneously on a host, each must have a unique display number. See the DISPLAY NAMES section of the X(3) manual page to learn how to specify which display number clients should try to use.
-ac disables host-based access control mechanisms. Enables access by any host, and permits any host to modify the access control list. Use with extreme caution. This option exists primarily for running test suites remotely.
-audit level Sets the audit trail level. The default level is 1, meaning only connection rejections are reported. Level 2 additionally reports all successful connections and disconnects. Level 0 turns off the audit trail. Audit lines are sent as standard error output.
-auth authorization-file Specifies a file which contains a collection of authorization records used to authenticate access. See also the xdm and Xsecurity manual pages.
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.
-cmdkey alt specifies that the Macintosh Command (Apple) key will be used as an X Alt key. The default operation of the Macintosh Command key is the X Meta character.
-co filename sets name of RGB color database. The default is <XRoot>/lib/X11/rgb, where <XRoot> refers to the root of the X11 install tree.
-config filename reads more options from the given file. Options in the file may be separated by newlines if desired. If a '#' character appears on a line, all characters between it and the next newline are ignored, providing a simple commenting facility. The -config option itself may appear in the file.
-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.
-deferglyphs whichfonts specifies the types of fonts for which the server should attempt to use deferred glyph loading. whichfonts can be all (all fonts),
-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 X server searches for font databases.
-fs starts the server in full screen mode. In this mode, the Macintosh menu bar is hidden by the X desktop. Pull down menus from the Mac menu bar remain accessible by pressing the mouse button while dragging the cursor along the top edge of the X desktop.
-help prints a usage message.
-I causes all remaining command line arguments to be ignored.
-mbm middle-key changes the middle mouse button keystroke mapping from the default <left arrow> key. The key is entered as a decimal value representing the Macintosh virtual key code corresponding to the desired key. Allowable values are between 0 and 127.
-mbr right-key changes the right mouse button keystroke mapping from the default <right arrow> key.
-menu starts the server in dedicated full screen mode. In this mode, the Macintosh menu bar is hidden and access to Mac pull down menus is completely disabled. Access to the Macintosh desktop is allowed only via the xtmenu(9) program. Use this option with extreme caution, as it effectively locks out the Macintosh desktop GUI enviroment when the X desktop is visible!
-mo specifies that the Macintosh Option key will be used in combination with the mouse button keystroke to simulate the middle or right mouse button. When used without the -mbm or -mbr start up options, the default middle and right mouse button keystrokes become <Option-left arrow> and <Option-right arrow>, respectively. This option also causes the <up arrow> and <down arrow> keys to function normally.
-pn permits the server to continue running if it fails to establish all of its well-known sockets (connection points for clients), but establishes at least one.
-swc runs the server with a software cursor, allowing oversized X client specified cursors with a slight tradeoff in tactile response. Specifying this option will force the server to operate in full screen mode (refer to the "-menu" option).
-su disables save under support on all screens.
-terminate causes the server to terminate at server reset, instead of continuing to run.
-to seconds sets default connection timeout in seconds.
-tst disables all testing extensions (e.g., XTEST, XTrap, XTestExtension1).
ttyxx ignored, for servers started the ancient way (from init).
-wm forces the default backing-store of all windows to be WhenMapped. This is a backdoor way of getting backing-store to apply to all windows. Although all mapped windows will have backing store, the backing store attribute value reported by the server for a window will be the last value established by a client. If it has never been set by a client, the server will report the default value, NotUseful. This behavior is required by the X protocol, which allows the server to exceed the client's backing store expectations but does not provide a way to tell the client that it is doing so.
-x extension loads the specified extension at init. This is a no-op for most implementations.
-ld kilobytes 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.
-lf files 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.
-ls kilobytes 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.
-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.
-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 is very private, being on the command line!).
-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.
-xkbdir directory base directory for keyboard layout files
-xkbmap filename keyboard description to load on startup
[+-]accessx enable(+) or disable(-) AccessX key sequences
Many servers also have device-specific command line options. See the manual pages for the individual servers for more details.
Authorization data required by the above protocols 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. See xauth(1) for maintenance of this file, and distribution of its contents to remote hosts.
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 /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.
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 might wish to make use of the hooks in the libraries and the server to provide additional security models.
SIGHUP SIGTERM 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 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 its parent process after it has set up the various connection schemes. Xdm uses this feature to recognize when connecting to the server is possible.
The default font path is "<XRoot>/lib/X11/fonts/misc/, <XRoot>/lib/X11/fonts/Speedo/, <XRoot>/lib/X11/fonts/Type1/, <XRoot>/lib/X11/fonts/75dpi/, <XRoot>/lib/X11/fonts/100dpi/ where <XRoot> refers to the root of the X11 install tree.
The font path can be set with the -fp option or by xset(1) after the server has started.
Font databases are created by running the mkfontdir program in the directory containing the compiled versions of the fonts (the .pcf 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.
/etc/Xn.hosts Initial access control list for display number n
<XRoot>/lib/X11/fonts/misc, <XRoot>/lib/X11/fonts/75dpi, <XRoot>/lib/X11/fonts/100dpi Bitmap font directories
<XRoot>/lib/X11/fonts/Speedo, <XRoot>/lib/X11/fonts/Type1 Outline font directories
<XRoot>/lib/X11/fonts/PEX PEX font directories
<XRoot>/lib/X11/rgb.txt Color database
/tmp/.X11-unix/Xn Unix domain socket for display number n
/tmp/rcXn Kerberos 5 replay cache for display number n
/usr/adm/Xnmsgs Error log file for display number n if run from init(8)
<XRoot>/lib/X11/xdm/xdm-errors Default error log file if the server is run from xdm(1)
Note: <XRoot> refers to the root of the X11 install tree.
Protocols: X Window System Protocol, The X Font Service Protocol, X Display Manager Control Protocol
Fonts: bdftopcf(1), mkfontdir(1), xfs(1), xlsfonts(1), xfontsel(1), xfd(1), X Logical Font Description Conventions
Security: Xsecurity(3), xauth(1), Xau(1), xdm(1), xhost(1)
Starting the server: xdm(1), xinit(1)
Controlling the server once started: xset(1), xsetroot(1), xhost(1)
Server-specific man pages: XMachTen(1), xtmenu(1), wind(8)
Server internal documentation: 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