NAME

Xserver - X Window System display server

SYNOPSIS

X [option ...]

DESCRIPTION

X is the generic name for the X Window System display 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.

STARTING THE SERVER

The X server is usually started from the X Display Manager program _x_d_m(1) or a similar display manager program. 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.

Installations that run more than one window system may need to use the _x_i_n_i_t(1) utility instead of a display manager. However, _x_i_n_i_t is to be considered a tool for building startup scripts and is not intended for use by end users. Site administrators are ssttrroonnggllyy urged to use a display manager, or build other interfaces for novice users.

The X server may also be started directly by the user, though this method is usually reserved for testing and is not recommended for normal operation. On some platforms, the user must have special permission to start the X server, often because access to certain devices (e.g. _/_d_e_v_/_m_o_u_s_e) is restricted.

When the X server starts up, it typically takes over the display. If you are running on a workstation whose console is the display, you may not be able to log into the console while the server is running.

OPTIONS

Many X servers have device-specific command line options. See the manual pages for the individual servers for more details; a list of server-specific manual pages is provided in the SEE ALSO section below.

All of the X servers accept the command line options described below. Some X servers may have alternative ways of providing the parameters described here, but the values provided via the command line options should override values specified via other mechanisms.

:_d_i_s_p_l_a_y_n_u_m_b_e_r
The X server runs as the given _d_i_s_p_l_a_y_n_u_m_b_e_r, 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(7) manual page to learn how to specify which display number clients should try to use.
-a _n_u_m_b_e_r
sets pointer acceleration (i.e. the ratio of how much is reported to how much the user actually moved the pointer).
-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 _l_e_v_e_l
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 4 enables messages from the SECURITY extension, if present, including generation and revocation of authorizations and violations of the security policy. Level 0 turns off the audit trail. Audit lines are sent as standard error output.
-auth _a_u_t_h_o_r_i_z_a_t_i_o_n_-_f_i_l_e
specifies a file which contains a collection of authorization records used to authenticate access. See also the _x_d_m(1) and _X_s_e_c_u_r_i_t_y(7) 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.
-br
sets the default root window to solid black instead of the standard root weave pattern.
-c
turns off key-click.
c _v_o_l_u_m_e
sets key-click volume (allowable range: 0-100).
-cc _c_l_a_s_s
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 _f_i_l_e_n_a_m_e
sets name of RGB color database. The default is /usr/X11R6/lib/X11/rgb.
-core
causes the server to generate a core dump on fatal errors.
-deferglyphs _w_h_i_c_h_f_o_n_t_s
specifies the types of fonts for which the server should attempt to use deferred glyph loading. _w_h_i_c_h_f_o_n_t_s can be all (all fonts), none (no fonts), or 16 (16 bit fonts only).
-dpi _r_e_s_o_l_u_t_i_o_n
sets the resolution for all screens, in dots per inch. To be used when the server cannot determine the screen size(s) from the hardware.
dpms
enables DPMS (display power management services), where supported. The default state is platform and configuration specific.
-dpms
disables DPMS (display power management services). The default state is platform and configuration specific.
-f _v_o_l_u_m_e
sets feep (bell) volume (allowable range: 0-100).
-fc _c_u_r_s_o_r_F_o_n_t
sets default cursor font.
-fn _f_o_n_t
sets the default font.
-fp _f_o_n_t_P_a_t_h
sets the search path for fonts. This path is a comma separated list of directories which the X server searches for font databases. See the FONTS section of this manual page for more information and the default list.
-help
prints a usage message.
-I
causes all remaining command line arguments to be ignored.
-maxbigreqsize _s_i_z_e
sets the maxmium big request to size MB.
-nolisten _t_r_a_n_s_-_t_y_p_e
disables a transport type. For example, TCP/IP connections can be disabled with -nolisten tcp. This option may be issued multiple times to disable listening to different transport types.
-noreset
prevents a server reset when the last client connection is closed. This overrides a previous -terminate command line option.
-p _m_i_n_u_t_e_s
sets screen-saver pattern cycle time in minutes.
-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. This option is set by default.
-nopn
causes the server to exit if it fails to establish all of its well-known sockets (connection points for clients).
-r
turns off auto-repeat.
r
turns on auto-repeat.
-s _m_i_n_u_t_e_s
sets screen-saver timeout time in minutes.
-su
disables save under support on all screens.
-t _n_u_m_b_e_r
sets pointer acceleration threshold in pixels (i.e. after how many pixels pointer acceleration should take effect).
-terminate
causes the server to terminate at server reset, instead of continuing to run. This overrides a previous -noreset command line option.
-to _s_e_c_o_n_d_s
sets default connection timeout in seconds.
-tst
disables all testing extensions (e.g., XTEST, XTrap, XTestExtension1, RECORD).
tty_x_x
ignored, for servers started the ancient way (from init).
v
sets video-off screen-saver preference.
-v
sets video-on screen-saver preference.
-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 _e_x_t_e_n_s_i_o_n
loads the specified extension at init. This is a no-op for most implementations.
[+-]xinerama
enables(+) or disables(-) the XINERAMA extension. The default state is platform and configuration specific.

SERVER DEPENDENT OPTIONS

Some X servers accept the following options:
-ld _k_i_l_o_b_y_t_e_s
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 _f_i_l_e_s
sets the number-of-open-files limit of the server to the specified number. A value of zero makes the limit as large as possible. The default value of -1 leaves the limit unchanged.
-ls _k_i_l_o_b_y_t_e_s
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.
-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.
-render
default|mono|gray|color sets the color allocation policy that will be used by the render extension.
default
selects the default policy defined for the display depth of the X server.
mono
don't use any color cell.
gray
use a gray map of 13 color cells for the X render extension.
color
use a color cube of at most 4*4*4 colors (that is 64 color cells).
-dumbSched
disables smart scheduling on platforms that support the smart scheduler.
-schedInterval _i_n_t_e_r_v_a_l
sets the smart scheduler's scheduling interval to interval milliseconds.

XDMCP OPTIONS

X servers that support XDMCP have the following options. See the _X _D_i_s_p_l_a_y _M_a_n_a_g_e_r _C_o_n_t_r_o_l _P_r_o_t_o_c_o_l specification for more information.
-query _h_o_s_t_n_a_m_e
enables XDMCP and sends Query packets to the specified hostname.
-broadcast
enable XDMCP and broadcasts BroadcastQuery packets to the network. The first responding display manager will be chosen for the session.
-multicast [_a_d_d_r_e_s_s [_h_o_p _c_o_u_n_t]]
Enable XDMCP and multicast BroadcastQuery packets to the network. The first responding display manager is chosen for the session. If an address is specified, the multicast is sent to that address. If no address is specified, the multicast is sent to the default XDMCP IPv6 multicast group. If a hop count is specified, it is used as the maximum hop count for the multicast. If no hop count is specified, the multicast is set to a maximum of 1 hop, to prevent the multicast from being routed beyond the local network.
-indirect _h_o_s_t_n_a_m_e
enables XDMCP and send IndirectQuery packets to the specified hostname.
-port _p_o_r_t_-_n_u_m_b_e_r
uses the specified _p_o_r_t_-_n_u_m_b_e_r for XDMCP packets, instead of the default. This option must be specified before any -query, -broadcast, -multicast, or -indirect options.
-from _l_o_c_a_l_-_a_d_d_r_e_s_s
specifies the local address to connect from (useful if the connecting host has multiple network interfaces). The _l_o_c_a_l_-_a_d_d_r_e_s_s may be expressed in any form acceptable to the host platform's _g_e_t_h_o_s_t_b_y_n_a_m_e(3) implementation.
-once
causes the server to terminate (rather than reset) when the XDMCP session ends.
-class _d_i_s_p_l_a_y_-_c_l_a_s_s
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 _x_d_m_-_a_u_t_h_-_b_i_t_s
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 _d_i_s_p_l_a_y_-_i_d
Yet another XDMCP specific value, this one allows the display manager to identify each display so that it can locate the shared key.

XKEYBOARD OPTIONS

X servers that support the XKEYBOARD (a.k.a. "XKB") extension accept the following options. All layout files specified on the command line must be located in the XKB base directory or a subdirectory, and specified as the relative path from the XKB base directory. The default XKB base directory is /usr/X11R6/lib/X11/xkb.
[+-]kb
enables(+) or disables(-) the XKEYBOARD extension.
[+-]accessx [ _t_i_m_e_o_u_t [ _t_i_m_e_o_u_t___m_a_s_k [ _f_e_e_d_b_a_c_k [ _o_p_t_i_o_n_s___m_a_s_k ] ] ] ]
enables(+) or disables(-) AccessX key sequences.
-xkbdir _d_i_r_e_c_t_o_r_y
base directory for keyboard layout files. This option is not available for setuid X servers (i.e., when the X server's real and effective uids are different).
-ar1 _m_i_l_l_i_s_e_c_o_n_d_s
sets the autorepeat delay (length of time in milliseconds that a key must be depressed before autorepeat starts).
-ar2 _m_i_l_l_i_s_e_c_o_n_d_s
sets the autorepeat interval (length of time in milliseconds that should elapse between autorepeat-generated keystrokes).
-noloadxkb
disables loading of an XKB keymap description on server startup.
-xkbdb _f_i_l_e_n_a_m_e
uses _f_i_l_e_n_a_m_e for default keyboard keymaps.
-xkbmap _f_i_l_e_n_a_m_e
loads keyboard description in _f_i_l_e_n_a_m_e on server startup.

SECURITY EXTENSION OPTIONS

X servers that support the SECURITY extension accept the following option:
-sp _f_i_l_e_n_a_m_e
causes the server to attempt to read and interpret filename as a security policy file with the format described below. The file is read at server startup and reread at each server reset.

The syntax of the security policy file is as follows. Notation: "*" means zero or more occurrences of the preceding element, and "+" means one or more occurrences. To interpret , ignore the text after the /; it is used to distinguish between instances of in the next section.


 ::=  *

::= '\n'

::= | | |

::= # * '\n'

::= '\n'

::= sitepolicy '\n'

::= property '\n'

::=

::= any | root |

::= |

::= =

::= [ | | ]*

::= r | w | d

::= a | i | e

::= | |

::= " * "

::= ' * '

::= +

::= [ ' ' | '\t' ]*

Character sets:

::= any character except '\n' ::= any character except " ::= any character except ' ::= any character except those in

The semantics associated with the above syntax are as follows.

, the first line in the file, specifies the file format version. If the server does not recognize the version , it ignores the rest of the file. The version string for the file format described here is "version-1" .

Once past the , lines that do not match the above syntax are ignored.

lines are ignored.

lines are currently ignored. They are intended to specify the site policies used by the XC-QUERY-SECURITY-1 authorization method.

lines specify how the server should react to untrusted client requests that affect the X Window property named . The rest of this section describes the interpretation of an .

For an to apply to a given instance of , must be on a window that is in the set of windows specified by . If is any, the rule applies to on any window. If is root, the rule applies to only on root windows.

If is , the following apply. If is a , the rule applies when the window also has that , regardless of its value. If is a , must also have the value specified by . In this case, the property must have type STRING and format 8, and should contain one or more null-terminated strings. If any of the strings match , the rule applies.

The definition of string matching is simple case-sensitive string comparison with one elaboration: the occurrence of the character '*' in is a wildcard meaning "any string." A can contain multiple wildcards anywhere in the string. For example, "x*" matches strings that begin with x, "*x" matches strings that end with x, "*x*" matches strings containing x, and "x*y*" matches strings that start with x and subsequently contain y.

There may be multiple lines for a given . The rules are tested in the order that they appear in the file. The first rule that applies is used.

specify operations that untrusted clients may attempt, and the actions that the server should take in response to those operations.

can be r (read), w (write), or d (delete). The following table shows how X Protocol property requests map to these operations in The Open Group server implementation.


GetProperty     r, or r and d if delete = True
ChangeProperty  w
RotateProperties        r and w
DeleteProperty  d
ListProperties  none, untrusted clients can always list all properties

can be a (allow), i (ignore), or e (error). Allow means execute the request as if it had been issued by a trusted client. Ignore means treat the request as a no-op. In the case of GetProperty, ignore means return an empty property value if the property exists, regardless of its actual value. Error means do not execute the request and return a BadAtom error with the atom set to the property name. Error is the default action for all properties, including those not listed in the security policy file.

An applies to all s that follow it, until the next is encountered. Thus, irwad means ignore read and write, allow delete.

GetProperty and RotateProperties may do multiple operations (r and d, or r and w). If different actions apply to the operations, the most severe action is applied to the whole request; there is no partial request execution. The severity ordering is: allow < ignore < error. Thus, if the for a property are ired (ignore read, error delete), and an untrusted client attempts GetProperty on that property with delete = True, an error is returned, but the property value is not. Similarly, if any of the properties in a RotateProperties do not allow both read and write, an error is returned without changing any property values.

Here is an example security policy file.


version-1

# Allow reading of application resources, but not writing. property RESOURCE_MANAGER root ar iw property SCREEN_RESOURCES root ar iw

# Ignore attempts to use cut buffers. Giving errors causes apps to crash, # and allowing access may give away too much information. property CUT_BUFFER0 root irw property CUT_BUFFER1 root irw property CUT_BUFFER2 root irw property CUT_BUFFER3 root irw property CUT_BUFFER4 root irw property CUT_BUFFER5 root irw property CUT_BUFFER6 root irw property CUT_BUFFER7 root irw

# If you are using Motif, you probably want these. property _MOTIF_DEFAULT_BINDINGS rootar iw property _MOTIF_DRAG_WINDOW root ar iw property _MOTIF_DRAG_TARGETS any ar iw property _MOTIF_DRAG_ATOMS any ar iw property _MOTIF_DRAG_ATOM_PAIRS any ar iw

# The next two rules let xwininfo -tree work when untrusted. property WM_NAME any ar

# Allow read of WM_CLASS, but only for windows with WM_NAME. # This might be more restrictive than necessary, but demonstrates # the facility, and is also an attempt to # say "top level windows only." property WM_CLASS WM_NAME ar

# These next three let xlsclients work untrusted. Think carefully # before including these; giving away the client machine name and command # may be exposing too much. property WM_STATE WM_NAME ar property WM_CLIENT_MACHINE WM_NAME ar property WM_COMMAND WM_NAME ar

# To let untrusted clients use the standard colormaps created by # xstdcmap, include these lines. property RGB_DEFAULT_MAP root ar property RGB_BEST_MAP root ar property RGB_RED_MAP root ar property RGB_GREEN_MAP root ar property RGB_BLUE_MAP root ar property RGB_GRAY_MAP root ar

# To let untrusted clients use the color management database created # by xcmsdb, include these lines. property XDCCC_LINEAR_RGB_CORRECTION rootar property XDCCC_LINEAR_RGB_MATRICES rootar property XDCCC_GRAY_SCREENWHITEPOINT rootar property XDCCC_GRAY_CORRECTION rootar

# To let untrusted clients use the overlay visuals that many vendors # support, include this line. property SERVER_OVERLAY_VISUALS rootar

# Dumb examples to show other capabilities.

# oddball property names and explicit specification of error conditions property "property with spaces" 'property with "'aw er ed

# Allow deletion of Woo-Hoo if window also has property OhBoy with value # ending in "son". Reads and writes will cause an error. property Woo-Hoo OhBoy = "*son"ad

NETWORK CONNECTIONS

The X server supports client connections via a platform-dependent subset of the following transport types: TCPIP, Unix Domain sockets, DECnet, and several varieties of SVR4 local connections. See the DISPLAY NAMES section of the _X(7) manual page to learn how to specify which transport type clients should try to use.

GRANTING ACCESS

The X server implements a platform-dependent subset of the following authorization protocols: MIT-MAGIC-COOKIE-1, XDM-AUTHORIZATION-1, XDM-AUTHORIZATION-2, SUN-DES-1, and MIT-KERBEROS-5. See the _X_s_e_c_u_r_i_t_y(7) manual page for information on the operation of these protocols.

Authorization data required by the above protocols is passed to the server in a private file named with the --aauutthh 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 _X_a_u manual page for a description of the binary format of this file. See _x_a_u_t_h(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 _/_e_t_c_/_Xnn_._h_o_s_t_s, where nn 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::) or a complete name in the format _f_a_m_i_l_y:_n_a_m_e as described in the _x_h_o_s_t(1) manual page. There should be no leading or trailing spaces on any lines. For example:


        joesworkstation
        corporate.company.com
        star::
        inet:bigcpu
        local:
        

Users can add or remove hosts from this list and enable or disable access control using the _x_h_o_s_t command from the same machine as the server.

If the X FireWall Proxy (_x_f_w_p) is being used without a sitepolicy, host-based authorization must be turned on for clients to be able to connect to the X server via the _x_f_w_p. If _x_f_w_p is run without a configuration file and thus no sitepolicy is defined, if _x_f_w_p is using an X server where xhost + has been run to turn off host-based authorization checks, when a client tries to connect to this X server via _x_f_w_p, the X server will deny the connection. See _x_f_w_p(1) for more information about this proxy.

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. X servers that support the SECURITY extension fare better because clients can be designated untrusted via the authorization they use to connect; see the _x_a_u_t_h(1) manual page for details. Restrictions are imposed on untrusted clients that curtail the mischief they can do. See the SECURITY extension specification for a complete list of these restrictions.

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.

SIGNALS

The X 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 main user's main application (usually an _x_t_e_r_m 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 its parent process after it has set up the various connection schemes. _X_d_m uses this feature to recognize when connecting to the server is possible.

FONTS

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 _f_o_n_t _p_a_t_h.

The default font path is __default_font_path__ .

The font path can be set with the --ffpp option or by _x_s_e_t(1) after the server has started.

FILES

/etc/Xnn.hosts
Initial access control list for display number nn
/usr/X11R6/lib/X11/fonts/misc,/usr/X11R6/lib/X11/fonts/75dpi,/usr/X11R6/lib/X11/fonts/100dpi
Bitmap font directories
/usr/X11R6/lib/X11/fonts/TTF,/usr/X11R6/lib/X11/fonts/Speedo,/usr/X11R6/lib/X11/fonts/Type1
Outline font directories
/usr/X11R6/lib/X11/rgb.txt
Color database
/tmp/.X11-unix/Xnn
Unix domain socket for display number nn
/tmp/rcXnn
Kerberos 5 replay cache for display number nn
/usr/adm/Xnnmsgs
Error log file for display number nn if run from _i_n_i_t(8)
/usr/X11R6/lib/X11/xdm/xdm-errors
Default error log file if the server is run from _x_d_m(1)

SEE ALSO

General information: _X(7)

Protocols: X Window System Protocol, The X Font Service Protocol, X Display Manager Control Protocol

Fonts: _b_d_f_t_o_p_c_f(1), _m_k_f_o_n_t_d_i_r(1), _m_k_f_o_n_t_s_c_a_l_e(1), _x_f_s(1), _x_l_s_f_o_n_t_s(1), _x_f_o_n_t_s_e_l(1), _x_f_d(1), X Logical Font Description Conventions

Security: _X_s_e_c_u_r_i_t_y(7), _x_a_u_t_h(1), _X_a_u(1), _x_d_m(1), _x_h_o_s_t(1), _x_f_w_p(1), Security Extension Specification

Starting the server: _x_d_m(1), _x_i_n_i_t(1)

Controlling the server once started: _x_s_e_t(1), _x_s_e_t_r_o_o_t(1), _x_h_o_s_t(1)

Server-specific man pages: _X_d_e_c(1), _X_m_a_c_I_I(1), _X_s_u_n(1), _X_n_e_s_t(1), _X_v_f_b(1), _X_F_r_e_e_8_6(1), _X_D_a_r_w_i_n(1).

Server internal documentation: Definition of the Porting Layer for the X v11 Sample Server

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. Dave Wiggins took over post-R5 and made substantial improvements.