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Xserver (1)
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    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 appropri-
         ate 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  xdm(1).   This  utility is run from the system boot
         files and takes care of keeping the server running,  prompt-
         ing  for  usernames  and passwords, and starting up the user
         sessions.
    
         Installations that run more than one window system may  need
         to  use the xinit(1) utility instead of xdm.  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 use xdm, 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. /dev/mouse) 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
         All of the X  servers  accept  the  following  command  line
         options:
    
         :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(1) manual page to learn how to  specify  which
                 display number clients should try to use.
    
         -a number
                 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 level
                 Sets the audit trail level.  The default level is 1,
                 meaning  only  connection  rejections  are reported.
                 Level 2 additionally reports all successful  connec-
                 tions  and  disconnects.   Level  4 enables messages
                 from the SECURITY extension, if  present,  including
                 generation and revocation of authorizations and vio-
                 lations of the security policy.  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.
    
         -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.   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.
    
         -core   causes the server to generate a core dump  on  fatal
                 errors.
    
         -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.  whi-
                 chfonts can be all (all fonts), none (no fonts),  or
                 16 (16 bit fonts only).
    
         -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 X
                 server searches for font databases.
    
         -help   prints a usage message.
    
         -I      causes all remaining command line  arguments  to  be
                 ignored.
    
         -kb     disables the XKEYBOARD extension if present.
    
         -p minutes
                 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 (connec-
                 tion points for clients), but establishes  at  least
                 one.
    
         -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).
    
         -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, RECORD).
    
         ttyxx   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 extension
                 loads the specified extension at init.   This  is  a
                 no-op for most implementations.
    
         [+-]xinerama
                 enable(+) or disable(-) XINERAMA extension.  Default
                 is disabled.
    
    SERVER DEPENDENT OPTIONS
         Some X servers accept the following options:
    
         -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 of 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.
    
         -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.
    
    XDMCP OPTIONS
         X servers that support XDMCP  have  the  following  options.
         See the X Display Manager Control Protocol specification for
         more information.
    
         -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.
    
    XKEYBOARD OPTIONS
         X servers that support the XKEYBOARD  extension  accept  the
         following options:
    
         -xkbdir directory
                 base directory for keyboard layout files
    
         -xkbmap filename
                 keyboard description to load on startup
    
         [+-]accessx
                 enable(+) or disable(-) AccessX key sequences
    
         -ar1 milliseconds
                 sets the length of time in milliseconds that  a  key
                 must be depressed before autorepeat starts
    
         -ar2 milliseconds
                 sets the length of time in milliseconds that  should
                 elapse between autorepeat-generated keystrokes
    
         Many servers also have device-specific command line options.
         See  the  manual  pages  for the individual servers for more
         details.
    
    SECURITY EXTENSION OPTIONS
         X servers that support the  SECURITY  extension  accept  the
         following option:
    
         -sp filename
                 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.  Nota-
         tion:  "*"  means  zero or more occurrences of the preceding
         element, and "+" means one or more occurrences.   To  inter-
         pret  <foo/bar>,  ignore the text after the /; it is used to
         distinguish between instances of <foo> in the next section.
    
         <policy file> ::= <version line> <other line>*
    
         <version line> ::= <string/v> '\n'
    
         <other line > ::= <comment> | <access rule> | <site policy> | <blank line>
    
         <comment> ::= # <not newline>* '\n'
    
         <blank line> ::= <space> '\n'
    
         <site policy> ::= sitepolicy <string/sp> '\n'
    
         <access rule> ::= property <property/ar> <window> <perms> '\n'
    
         <property> ::= <string>
    
         <window> ::= any | root | <required property>
    
         <required property> ::= <property/rp> | <property with value>
    
         <property with value> ::= <property/rpv> = <string/rv>
    
         <perms> ::= [ <operation> | <action> | <space> ]*
    
         <operation> ::= r | w | d
    
         <action> ::= a | i | e
    
         <string> ::= <dbl quoted string> | <single quoted string> | <unqouted string>
    
         <dbl quoted string> ::= <space> " <not dqoute>* " <space>
    
         <single quoted string> ::= <space> ' <not squote>* ' <space>
    
         <unquoted string> ::= <space> <not space>+ <space>
    
         <space> ::= [ ' ' | '\t' ]*
    
         Character sets:
    
         <not newline> ::= any character except '\n'
         <not dqoute>  ::= any character except "
         <not squote>  ::= any character except '
         <not space>   ::= any character except those in <space>
    
         The semantics associated with the above syntax are  as  fol-
         lows.
    
         <version line>, the first line in the  file,  specifies  the
         file  format  version.  If the server does not recognize the
         version <string/v>, it ignores the rest of  the  file.   The
         version  string  for  the  file  format  described  here  is
         "version-1" .
    
         Once past the <version line>, lines that do  not  match  the
         above syntax are ignored.
    
         <comment> lines are ignored.
    
         <sitepolicy> lines are currently ignored.  They are intended
         to specify the site policies used by the XC-QUERY-SECURITY-1
         authorization method.
    
         <access rule> lines specify how the server should  react  to
         untrusted  client requests that affect the X Window property
         named <property/ar>.  The rest of this section describes the
         interpretation of an <access rule>.
    
         For an <access  rule>  to  apply  to  a  given  instance  of
         <property/ar>,  <property/ar> must be on a window that is in
         the set of windows specified by <window>.   If  <window>  is
         any,  the  rule  applies to <property/ar> on any window.  If
         <window> is root, the rule applies to <property/ar> only  on
         root windows.
    
         If <window> is <required property>, the following apply.  If
         <required  property>  is  a  <property/rp>, the rule applies
         when the window also has that <property/rp>,  regardless  of
         its  value.   If  <required  property>  is  a <property with
         value>, <property/rpv> must also have the value specified by
         <string/rv>.   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
         <string/rv>, the rule applies.
    
         The definition of string matching is  simple  case-sensitive
         string comparison with one elaboration: the occurence of the
         character '*' in <string/rv>  is  a  wildcard  meaning  "any
         string."   A <string/rv> can contain multiple wildcards any-
         where 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  <access  rule>  lines  for  a  given
         <property/ar>.   The rules are tested in the order that they
         appear in the file.  The first rule that applies is used.
    
         <perms>  specify  operations  that  untrusted  clients   may
         attempt,  and  the  actions  that  the server should take in
         response to those operations.
    
         <operation> 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
    
         <action> 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 <action> applies to  all  <operation>s  that  follow  it,
         until  the next <action> 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 sever-
         ity ordering is: allow <  ignore  <  error.   Thus,  if  the
         <perms> for a property are ired (ignore read, error delete),
         and an untrusted client attempts GetProperty  on  that  pro-
         perty with delete = True, an error is returned, but the pro-
         perty 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 <required property> 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: TCP/IP,
         Unix Domain sockets, DECnet, and several varieties  of  SVR4
         local  connections.   See  the  DISPLAY NAMES section of the
         X(1) 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, SUN-DES-1,  and  MIT-KERBEROS-5.   See  the
         Xsecurity(1) 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 -auth command
         line option.  Each time the server is about  to  accept  the
         first connection after a reset (or when the server is start-
         ing), it reads this file.  If this file contains any author-
         ization 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 connec-
         tion 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  dis-
         tribution 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  mechan-
         ism  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.
    
         If the X FireWall Proxy  (xfwp)  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  xfwp.
         If  xfwp  is  run  without  a configuration file and thus no
         sitepolicy is defined, if xfwp 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
         xfwp,  the  X  server will deny the connection.  See xfwp(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 desig-
         nated  untrusted  via the authorization they use to connect;
         see the xauth(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 com-
         plete list of these restrictions.
    
         Sites that have better authentication and authorization sys-
         tems  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  sig-
         nals:
    
         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 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.
    
    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 font path.
    
         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.
    
    FILES
         /etc/Xn.hosts                 Initial  access  control  list
                                       for display number n
    
    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.
    
    SEE ALSO
         General information: X(1)
    
         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(1), xauth(1), Xau(1), xdm(1),  xhost(1),
         xfwp(1) Security Extension Specification
    
         Starting the server: xdm(1), xinit(1)
    
         Controlling the server once started:  xset(1),  xsetroot(1),
         xhost(1)
         Server-specific  man  pages:  Xdec(1),  XmacII(1),  Xsun(1),
         Xnest(6),      Xvfb(6),     XF86_Accel(1),     XF86_Mono(1),
         XF86_SVGA(1), XF86_VGA16(1), XFree86(1)
    
         Server internal documentation:  Definition  of  the  Porting
         Layer for the X v11 Sample Server
    
    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.   Dave  Wiggins
         took over post-R5 and made substantial improvements.
    
    
    
    


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