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     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	  xdm - X Display Manager with support for XDMCP, host chooser

	  xdm [ -config configuration_file ] [ -nodaemon ] [ -debug
	  debug_level ] [ -error error_log_file ] [ -resources
	  resource_file ] [ -server server_entry ] [ -session
	  session_program ]

	  Xdm manages a collection of X displays, which may be on the
	  local host or remote servers.	 The design of xdm was guided
	  by the needs of X terminals as well as the X Consortium
	  standard XDMCP, the X Display Manager Control Protocol.  Xdm
	  provides services similar to those provided by init, getty
	  and login on character terminals: prompting for login name
	  and password, authenticating the user, and running a

	  A ``session'' is defined by the lifetime of a particular
	  process; in the traditional character-based terminal world,
	  it is the user's login shell.	 In the xdm context, it is an
	  arbitrary session manager.  This is because in a windowing
	  environment, a user's login shell process does not
	  necessarily have any terminal-like interface with which to
	  connect.  When a real session manager is not available, a
	  window manager or terminal emulator is typically used as the
	  ``session manager,'' meaning that termination of this
	  process terminates the user's session.

	  When the session is terminated, xdm resets the X server and
	  (optionally) restarts the whole process.

	  When xdm receives an Indirect query via XDMCP, it can run a
	  chooser process to perform an XDMCP BroadcastQuery (or an
	  XDMCP Query to specified hosts) on behalf of the display and
	  offer a menu of possible hosts that offer XDMCP display
	  management.  This feature is useful with X terminals that do
	  not offer a host menu themselves.

	  Because xdm provides the first interface that users will
	  see, it is designed to be simple to use and easy to
	  customize to the needs of a particular site.	Xdm has many
	  options, most of which have reasonable defaults.  Browse
	  through the various sections of this manual, picking and
	  choosing the things you want to change.  Pay particular
	  attention to the Session Program section, which will
	  describe how to set up the style of session desired.

	  xdm is highly configurable, and most of its behavior can be
	  controlled by resource files and shell scripts.  The names

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     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	  of these files themselves are resources read from the file
	  xdm-config or the file named by the -config option.

	  xdm offers display management two different ways.  It can
	  manage X servers running on the local machine and specified
	  in Xservers, and it can manage remote X servers (typically X
	  terminals) using XDMCP (the XDM Control Protocol) as
	  specified in the Xaccess file.

	  The resources of the X clients run by xdm outside the user's
	  session, including xdm's own login window, can be affected
	  by setting resources in the Xresources file.

	  For X terminals that do not offer a menu of hosts to get
	  display management from, xdm can collect willing hosts and
	  run the chooser program to offer the user a menu.  For X
	  displays attached to a host, this step is typically not
	  used, as the local host does the display management.

	  After resetting the X server, xdm runs the Xsetup script to
	  assist in setting up the screen the user sees along with the
	  xlogin widget.

	  When the user logs in, xdm runs the Xstartup script as root.

	  Then xdm runs the Xsession script as the user.  This system
	  session file may do some additional startup and typically
	  runs a script in the user's home directory.  When the
	  Xsession script exits, the session is over.

	  At the end of the session, the Xreset script is run to clean
	  up, the X server is reset, and the cycle starts over.

	  The file /usr/X11R6/lib/X11/xdm/xdm-errors will contain
	  error messages from xdm and anything output to stderr by
	  Xsetup, Xstartup, Xsession or Xreset.	 When you have trouble
	  getting xdm working, check this file to see if xdm has any
	  clues to the trouble.

	  All of these options, except -config itself, specify values
	  that can also be specified in the configuration file as

	  -config configuration_file
	       Names the configuration file, which specifies resources
	       to control the behavior of xdm.
	       <XRoot>/lib/X11/xdm/xdm-config is the default.  See the
	       section Configuration File.

	       Specifies ``false'' as the value for the

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	       DisplayManager.daemonMode resource.  This suppresses
	       the normal daemon behavior, which is for xdm to close
	       all file descriptors, disassociate itself from the
	       controlling terminal, and put itself in the background
	       when it first starts up.

	  -debug debug_level
	       Specifies the numeric value for the
	       DisplayManager.debugLevel resource.  A non-zero value
	       causes xdm to print lots of debugging statements to the
	       terminal; it also disables the
	       DisplayManager.daemonMode resource, forcing xdm to run
	       synchronously.  To interpret these debugging messages,
	       a copy of the source code for xdm is almost a
	       necessity.  No attempt has been made to rationalize or
	       standardize the output.

	  -error error_log_file
	       Specifies the value for the DisplayManager.errorLogFile
	       resource.  This file contains errors from xdm as well
	       as anything written to stderr by the various scripts
	       and programs run during the progress of the session.

	  -resources resource_file
	       Specifies the value for the DisplayManager*resources
	       resource.  This file is loaded using xrdb to specify
	       configuration parameters for the authentication widget.

	  -server server_entry
	       Specifies the value for the DisplayManager.servers
	       resource.  See the section Local Server Specification
	       for a description of this resource.

	  -udpPort port_number
	       Specifies the value for the DisplayManager.requestPort
	       resource.  This sets the port-number which xdm will
	       monitor for XDMCP requests.  As XDMCP uses the
	       registered well-known UDP port 177, this resource
	       should not be changed except for debugging.

	  -session session_program
	       Specifies the value for the DisplayManager*session
	       resource.  This indicates the program to run as the
	       session after the user has logged in.

	  -xrm resource_specification
	       Allows an arbitrary resource to be specified, as in
	       most X Toolkit applications.

	  At many stages the actions of xdm can be controlled through
	  the use of its configuration file, which is in the X

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	  resource format.  Some resources modify the behavior of xdm
	  on all displays, while others modify its behavior on a
	  single display.  Where actions relate to a specific display,
	  the display name is inserted into the resource name between
	  ``DisplayManager'' and the final resource name segment.

	  For local displays, the resource name and class are as read
	  from the Xservers file.

	  For remote displays, the resource name is what the network
	  address of the display resolves to.  See the removeDomain
	  resource.  The name must match exactly; xdm is not aware of
	  all the network aliases that might reach a given display.
	  If the name resolve fails, the address is used.  The
	  resource class is as sent by the display in the XDMCP Manage

	  Because the resource manager uses colons to separate the
	  name of the resource from its value and dots to separate
	  resource name parts, xdm substitutes underscores for both
	  dots and colons when generating the resource name.  For
	  example, DisplayManager.expo_x_org_0.startup is the name of
	  the resource which defines the startup shell file for the
	  ``expo.x.org:0'' display.

	       This resource either specifies a file name full of
	       server entries, one per line (if the value starts with
	       a slash), or a single server entry.  See the section
	       Local Server Specification for the details.

	       This indicates the UDP port number which xdm uses to
	       listen for incoming XDMCP requests.  Unless you need to
	       debug the system, leave this with its default value of

	       Error output is normally directed at the system
	       console.	 To redirect it, set this resource to a file
	       name.  A method to send these messages to syslog should
	       be developed for systems which support it; however, the
	       wide variety of interfaces precludes any system-
	       independent implementation.  This file also contains
	       any output directed to stderr by the Xsetup, Xstartup,
	       Xsession and Xreset files, so it will contain
	       descriptions of problems in those scripts as well.

	       If the integer value of this resource is greater than
	       zero, reams of debugging information will be printed.
	       It also disables daemon mode, which would redirect the

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	       information into the bit-bucket, and allows non-root
	       users to run xdm, which would normally not be useful.

	       Normally, xdm attempts to make itself into a daemon
	       process unassociated with any terminal.	This is
	       accomplished by forking and leaving the parent process
	       to exit, then closing file descriptors and releasing
	       the controlling terminal.  In some environments this is
	       not desired (in particular, when debugging).  Setting
	       this resource to ``false'' will disable this feature.

	       The filename specified will be created to contain an
	       ASCII representation of the process-id of the main xdm
	       process.	 Xdm also uses file locking on this file to
	       attempt to eliminate multiple daemons running on the
	       same machine, which would cause quite a bit of havoc.

	       This is the resource which controls whether xdm uses
	       file locking to keep multiple display managers from
	       running amok.  On System V, this uses the lockf library
	       call, while on BSD it uses flock.

	       This names a directory in which xdm stores
	       authorization files while initializing the session.
	       The default value is <XRoot>/lib/X11/xdm.

	       This boolean controls whether xdm rescans the
	       configuration, servers, access control and
	       authentication keys files after a session terminates
	       and the files have changed.  By default it is ``true.''
	       You can force xdm to reread these files by sending a
	       SIGHUP to the main process.

	       When computing the display name for XDMCP clients, the
	       name resolver will typically create a fully qualified
	       host name for the terminal.  As this is sometimes
	       confusing, xdm will remove the domain name portion of
	       the host name if it is the same as the domain name of
	       the local host when this variable is set.  By default
	       the value is ``true.''

	       XDM-AUTHENTICATION-1 style XDMCP authentication
	       requires that a private key be shared between xdm and
	       the terminal.  This resource specifies the file
	       containing those values.	 Each entry in the file

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	       consists of a display name and the shared key.  By
	       default, xdm does not include support for XDM-
	       AUTHENTICATION-1, as it requires DES which is not
	       generally distributable because of United States export

	       To prevent unauthorized XDMCP service and to allow
	       forwarding of XDMCP IndirectQuery requests, this file
	       contains a database of hostnames which are either
	       allowed direct access to this machine, or have a list
	       of hosts to which queries should be forwarded to.  The
	       format of this file is described in the section XDMCP
	       Access Control.

	       A list of additional environment variables, separated
	       by white space, to pass on to the Xsetup, Xstartup,
	       Xsession, and Xreset programs.

	       A file to checksum to generate the seed of
	       authorization keys.  This should be a file that changes
	       frequently.  The default is /dev/mem.

	       On systems that support a dynamically-loadable greeter
	       library, the name of the library.  Default is

	       Number of seconds to wait for display to respond after
	       user has selected a host from the chooser.  If the
	       display sends an XDMCP IndirectQuery within this time,
	       the request is forwarded to the chosen host.
	       Otherwise, it is assumed to be from a new session and
	       the chooser is offered again.  Default is 15.

	       This resource specifies the name of the file to be
	       loaded by xrdb as the resource database onto the root
	       window of screen 0 of the display.  The Xsetup program,
	       the Login widget, and chooser will use the resources
	       set in this file.  This resource data base is loaded
	       just before the authentication procedure is started, so
	       it can control the appearance of the login window.  See
	       the section Authentication Widget, which describes the
	       various resources that are appropriate to place in this
	       file.  There is no default value for this resource, but
	       <XRoot>/lib/X11/xdm/Xresources is the conventional

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	       Specifies the program run to offer a host menu for
	       Indirect queries redirected to the special host name
	       CHOOSER.	 <XRoot>/lib/X11/xdm/chooser is the default.
	       See the sections XDMCP Access Control and Chooser.

	       Specifies the program used to load the resources.  By
	       default, xdm uses <XRoot>/bin/xrdb.

	       This specifies the name of the C preprocessor which is
	       used by xrdb.

	       This specifies a program which is run (as root) before
	       offering the Login window.  This may be used to change
	       the appearance of the screen around the Login window or
	       to put up other windows (e.g., you may want to run
	       xconsole here).	By default, no program is run.	The
	       conventional name for a file used here is Xsetup.  See
	       the section Setup Program.

	       This specifies a program which is run (as root) after
	       the authentication process succeeds.  By default, no
	       program is run.	The conventional name for a file used
	       here is Xstartup.  See the section Startup Program.

	       This specifies the session to be executed (not running
	       as root).  By default, <XRoot>/bin/xterm is run.	 The
	       conventional name is Xsession.  See the section Session

	       This specifies a program which is run (as root) after
	       the session terminates.	Again, by default no program
	       is run.	The conventional name is Xreset.  See the
	       section Reset Program.




	       These numeric resources control the behavior of xdm
	       when attempting to open intransigent servers.
	       openDelay is the length of the pause (in seconds)
	       between successive attempts, openRepeat is the number

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	       of attempts to make, openTimeout is the amount of time
	       to wait while actually attempting the open (i.e., the
	       maximum time spent in the connect(2) system call) and
	       startAttempts is the number of times this entire
	       process is done before giving up on the server.	After
	       openRepeat attempts have been made, or if openTimeout
	       seconds elapse in any particular attempt, xdm
	       terminates and restarts the server, attempting to
	       connect again.  This process is repeated startAttempts
	       times, at which point the display is declared dead and
	       disabled.  Although this behavior may seem arbitrary,
	       it has been empirically developed and works quite well
	       on most systems.	 The default values are 5 for
	       openDelay, 5 for openRepeat, 30 for openTimeout and 4
	       for startAttempts.


	       To discover when remote displays disappear, xdm
	       occasionally pings them, using an X connection and
	       XSync calls.  pingInterval specifies the time (in
	       minutes) between each ping attempt, pingTimeout
	       specifies the maximum amount of time (in minutes) to
	       wait for the terminal to respond to the request.	 If
	       the terminal does not respond, the session is declared
	       dead and terminated.  By default, both are set to 5
	       minutes.	 If you frequently use X terminals which can
	       become isolated from the managing host, you may wish to
	       increase this value.  The only worry is that sessions
	       will continue to exist after the terminal has been
	       accidentally disabled.  xdm will not ping local
	       displays.  Although it would seem harmless, it is
	       unpleasant when the workstation session is terminated
	       as a result of the server hanging for NFS service and
	       not responding to the ping.

	       This boolean resource specifies whether the X server
	       should be terminated when a session terminates (instead
	       of resetting it).  This option can be used when the
	       server tends to grow without bound over time, in order
	       to limit the amount of time the server is run.  The
	       default value is ``false.''

	       Xdm sets the PATH environment variable for the session
	       to this value.  It should be a colon separated list of
	       directories; see sh(1) for a full description.
	       ``:/bin:/usr/bin:/usr/X11R6/bin:/usr/ucb'' is a common
	       setting.	 The default value can be specified at build
	       time in the X system configuration file with

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	       Xdm sets the PATH environment variable for the startup
	       and reset scripts to the value of this resource.	 The
	       default for this resource is specified at build time by
	       the DefaultSystemPath entry in the system configuration
	       file; ``/etc:/bin:/usr/bin:/usr/X11R6/bin:/usr/ucb'' is
	       a common choice.	 Note the absence of ``.'' from this
	       entry.  This is a good practice to follow for root; it
	       avoids many common Trojan Horse system penetration

	       Xdm sets the SHELL environment variable for the startup
	       and reset scripts to the value of this resource.	 It is
	       /bin/sh by default.

	       If the default session fails to execute, xdm will fall
	       back to this program.  This program is executed with no
	       arguments, but executes using the same environment
	       variables as the session would have had (see the
	       section Session Program).  By default,
	       <XRoot>/bin/xterm is used.


	       To improve security, xdm grabs the server and keyboard
	       while reading the login name and password.  The
	       grabServer resource specifies if the server should be
	       held for the duration of the name/password reading.
	       When ``false,'' the server is ungrabbed after the
	       keyboard grab succeeds, otherwise the server is grabbed
	       until just before the session begins.  The default is
	       ``false.''  The grabTimeout resource specifies the
	       maximum time xdm will wait for the grab to succeed.
	       The grab may fail if some other client has the server
	       grabbed, or possibly if the network latencies are very
	       high.  This resource has a default value of 3 seconds;
	       you should be cautious when raising it, as a user can
	       be spoofed by a look-alike window on the display.  If
	       the grab fails, xdm kills and restarts the server (if
	       possible) and the session.


	       authorize is a boolean resource which controls whether
	       xdm generates and uses authorization for the local
	       server connections.  If authorization is used, authName

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	       is a list of authorization mechanisms to use, separated
	       by white space.	XDMCP connections dynamically specify
	       which authorization mechanisms are supported, so
	       authName is ignored in this case.  When authorize is
	       set for a display and authorization is not available,
	       the user is informed by having a different message
	       displayed in the login widget.  By default, authorize
	       is ``true.''  authName is ``MIT-MAGIC-COOKIE-1,'' or,
	       if XDM-AUTHORIZATION-1 is available, ``XDM-

	       This file is used to communicate the authorization data
	       from xdm to the server, using the -auth server command
	       line option.  It should be kept in a directory which is
	       not world-writable as it could easily be removed,
	       disabling the authorization mechanism in the server.

	       If set to ``false,'' disables the use of the
	       unsecureGreeting in the login window.  See the section
	       Authentication Widget.  The default is ``true.''

	       The number of the signal xdm sends to reset the server.
	       See the section Controlling the Server.	The default is
	       1 (SIGHUP).

	       The number of the signal xdm sends to terminate the
	       server.	See the section Controlling the Server.	 The
	       default is 15 (SIGTERM).

	       The original implementation of authorization in the
	       sample server reread the authorization file at server
	       reset time, instead of when checking the initial
	       connection.  As xdm generates the authorization
	       information just before connecting to the display, an
	       old server would not get up-to-date authorization
	       information.  This resource causes xdm to send SIGHUP
	       to the server after setting up the file, causing an
	       additional server reset to occur, during which time the
	       new authorization information will be read.  The
	       default is ``false,'' which will work for all MIT

	       When xdm is unable to write to the usual user
	       authorization file ($HOME/.Xauthority), it creates a
	       unique file name in this directory and points the
	       environment variable XAUTHORITY at the created file.

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	       It uses /tmp by default.

	  First, the xdm configuration file should be set up.  Make a
	  directory (usually <XRoot>/lib/X11/xdm, where <XRoot> refers
	  to the root of the X11 install tree) to contain all of the
	  relevant files.  In the examples that follow, we use
	  /usr/X11R6 as the value of <XRoot>.

	  Here is a reasonable configuration file, which could be
	  named xdm-config:

	       DisplayManager.servers:		  /usr/X11R6/lib/X11/xdm/Xservers
	       DisplayManager.errorLogFile:	  /usr/X11R6/lib/X11/xdm/xdm-errors
	       DisplayManager*resources:	  /usr/X11R6/lib/X11/xdm/Xresources
	       DisplayManager*startup:		  /usr/X11R6/lib/X11/xdm/Xstartup
	       DisplayManager*session:		  /usr/X11R6/lib/X11/xdm/Xsession
	       DisplayManager.pidFile:		  /usr/X11R6/lib/X11/xdm/xdm-pid
	       DisplayManager._0.authorize:	  true
	       DisplayManager*authorize:	  false

	  Note that this file mostly contains references to other
	  files.  Note also that some of the resources are specified
	  with ``*'' separating the components.	 These resources can
	  be made unique for each different display, by replacing the
	  ``*'' with the display-name, but normally this is not very
	  useful.  See the Resources section for a complete

	  The database file specified by the DisplayManager.accessFile
	  provides information which xdm uses to control access from
	  displays requesting XDMCP service.  This file contains three
	  types of entries:  entries which control the response to
	  Direct and Broadcast queries, entries which control the
	  response to Indirect queries, and macro definitions.

	  The format of the Direct entries is simple, either a host
	  name or a pattern, which is distinguished from a host name
	  by the inclusion of one or more meta characters (`*' matches
	  any sequence of 0 or more characters, and `?' matches any
	  single character) which are compared against the host name
	  of the display device.  If the entry is a host name, all
	  comparisons are done using network addresses, so any name
	  which converts to the correct network address may be used.
	  For patterns, only canonical host names are used in the
	  comparison, so ensure that you do not attempt to match
	  aliases.  Preceding either a host name or a pattern with a
	  `!' character causes hosts which match that entry to be

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	  An Indirect entry also contains a host name or pattern, but
	  follows it with a list of host names or macros to which
	  indirect queries should be sent.

	  A macro definition contains a macro name and a list of host
	  names and other macros that the macro expands to.  To
	  distinguish macros from hostnames, macro names start with a
	  `%' character.  Macros may be nested.

	  Indirect entries may also specify to have xdm run chooser to
	  offer a menu of hosts to connect to.	See the section

	  When checking access for a particular display host, each
	  entry is scanned in turn and the first matching entry
	  determines the response.  Direct and Broadcast entries are
	  ignored when scanning for an Indirect entry and vice-versa.

	  Blank lines are ignored, `#' is treated as a comment
	  delimiter causing the rest of that line to be ignored, and
	  `\newline' causes the newline to be ignored, allowing
	  indirect host lists to span multiple lines.

	  Here is an example Xaccess file:

	  # Xaccess - XDMCP access control file

	  # Direct/Broadcast query entries

	  !xtra.lcs.mit.edu   # disallow direct/broadcast service for xtra
	  bambi.ogi.edu	      # allow access from this particular display
	  *.lcs.mit.edu	      # allow access from any display in LCS

	  # Indirect query entries

	  %HOSTS	      expo.lcs.mit.edu xenon.lcs.mit.edu \
			      excess.lcs.mit.edu kanga.lcs.mit.edu

	  extract.lcs.mit.edu xenon.lcs.mit.edu	  #force extract to contact xenon
	  !xtra.lcs.mit.edu   dummy		  #disallow indirect access
	  *.lcs.mit.edu	      %HOSTS		  #all others get to choose

	  For X terminals that do not offer a host menu for use with
	  Broadcast or Indirect queries, the chooser program can do
	  this for them.  In the Xaccess file, specify ``CHOOSER'' as

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	  the first entry in the Indirect host list.  Chooser will
	  send a Query request to each of the remaining host names in
	  the list and offer a menu of all the hosts that respond.

	  The list may consist of the word ``BROADCAST,'' in which
	  case chooser will send a Broadcast instead, again offering a
	  menu of all hosts that respond.  Note that on some operating
	  systems, UDP packets cannot be broadcast, so this feature
	  will not work.

	  Example Xaccess file using chooser:

	  extract.lcs.mit.edu CHOOSER %HOSTS	  #offer a menu of these hosts
	  xtra.lcs.mit.edu    CHOOSER BROADCAST	  #offer a menu of all hosts

	  The program to use for chooser is specified by the
	  DisplayManager.DISPLAY.chooser resource.  For more
	  flexibility at this step, the chooser could be a shell
	  script.  Chooser is the session manager here; it is run
	  instead of a child xdm to manage the display.

	  Resources for this program can be put into the file named by

	  When the user selects a host, chooser prints the host
	  chosen, which is read by the parent xdm, and exits.  xdm
	  closes its connection to the X server, and the server resets
	  and sends another Indirect XDMCP request.  xdm remembers the
	  user's choice (for DisplayManager.choiceTimeout seconds) and
	  forwards the request to the chosen host, which starts a
	  session on that display.

	  The resource DisplayManager.servers gives a server
	  specification or, if the values starts with a slash (/), the
	  name of a file containing server specifications, one per

	  Each specification indicates a display which should
	  constantly be managed and which is not using XDMCP.  This
	  method is used typically for local servers only.  If the
	  resource or the file named by the resource is empty, xdm
	  will offer XDMCP service only.

	  Each specification consists of at least three parts:	a
	  display name, a display class, a display type, and (for
	  local servers) a command line to start the server.  A
	  typical entry for local display number 0 would be:

	    :0 Digital-QV local /usr/X11R6/bin/X :0

	  The display types are:

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     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	  local	    local display: xdm must run the server
	  foreign   remote display: xdm opens an X connection to a running server

	  The display name must be something that can be passed in the
	  -display option to an X program.  This string is used to
	  generate the display-specific resource names, so be careful
	  to match the names (e.g., use ``:0 Sun-CG3 local
	  /usr/X11R6/bin/X :0'' instead of ``localhost:0 Sun-CG3 local
	  /usr/X11R6/bin/X :0'' if your other resources are specified
	  as ``DisplayManager._0.session'').  The display class
	  portion is also used in the display-specific resources, as
	  the class of the resource.  This is useful if you have a
	  large collection of similar displays (such as a corral of X
	  terminals) and would like to set resources for groups of
	  them.	 When using XDMCP, the display is required to specify
	  the display class, so the manual for your particular X
	  terminal should document the display class string for your
	  device.  If it doesn't, you can run xdm in debug mode and
	  look at the resource strings which it generates for that
	  device, which will include the class string.

	  When xdm starts a session, it sets up authorization data for
	  the server.  For local servers, xdm passes ``-auth
	  filename'' on the server's command line to point it at its
	  authorization data.  For XDMCP servers, xdm passes the
	  authorization data to the server via the Accept XDMCP

	  The Xresources file is loaded onto the display as a resource
	  database using xrdb. As the authentication widget reads this
	  database before starting up, it usually contains parameters
	  for that widget:

	       xlogin*login.translations: #override\
		    Ctrl<Key>R: abort-display()\n\
		    <Key>F1: set-session-argument(failsafe) finish-field()\n\
		    <Key>Return: set-session-argument() finish-field()
	       xlogin*borderWidth: 3
	       xlogin*greeting: CLIENTHOST
	       #ifdef COLOR
	       xlogin*greetColor: CadetBlue
	       xlogin*failColor: red

	  Please note the translations entry; it specifies a few new
	  translations for the widget which allow users to escape from
	  the default session (and avoid troubles that may occur in
	  it).	Note that if #override is not specified, the default
	  translations are removed and replaced by the new value, not

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     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	  a very useful result as some of the default translations are
	  quite useful (such as ``<Key>: insert-char ()'' which
	  responds to normal typing).

	  This file may also contain resources for the setup program
	  and chooser.

	  The Xsetup file is run after the server is reset, but before
	  the Login window is offered.	The file is typically a shell
	  script.  It is run as root, so should be careful about
	  security.  This is the place to change the root background
	  or bring up other windows that should appear on the screen
	  along with the Login widget.

	  In addition to any specified by DisplayManager.exportList,
	  the following environment variables are passed:

	       DISPLAY	      the associated display name
	       PATH	      the value of DisplayManager.DISPLAY.systemPath
	       SHELL	      the value of DisplayManager.DISPLAY.systemShell
	       XAUTHORITY     may be set to an authority file

	  Note that since xdm grabs the keyboard, any other windows
	  will not be able to receive keyboard input.  They will be
	  able to interact with the mouse, however; beware of
	  potential security holes here.  If
	  DisplayManager.DISPLAY.grabServer is set, Xsetup will not be
	  able to connect to the display at all.  Resources for this
	  program can be put into the file named by

	  Here is a sample Xsetup script:

	       # Xsetup_0 - setup script for one workstation
	       xcmsdb < /usr/X11R6/lib/monitors/alex.0
	       xconsole -geometry 480x130-0-0 -notify -verbose -exitOnFail &

	  The authentication widget reads a name/password pair from
	  the keyboard.	 Nearly every imaginable parameter can be
	  controlled with a resource.  Resources for this widget
	  should be put into the file named by
	  DisplayManager.DISPLAY.resources.  All of these have
	  reasonable default values, so it is not necessary to specify
	  any of them.

	  xlogin.Login.width, xlogin.Login.height, xlogin.Login.x,
	       The geometry of the Login widget is normally computed

     Page 15					    (printed 12/16/98)

     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	       automatically.  If you wish to position it elsewhere,
	       specify each of these resources.

	       The color used to display the typed-in user name.

	       The font used to display the typed-in user name.

	       A string which identifies this window.  The default is
	       ``X Window System.''

	       When X authorization is requested in the configuration
	       file for this display and none is in use, this greeting
	       replaces the standard greeting.	The default is ``This
	       is an unsecure session''

	       The font used to display the greeting.

	       The color used to display the greeting.

	       The string displayed to prompt for a user name.	Xrdb
	       strips trailing white space from resource values, so to
	       add spaces at the end of the prompt (usually a nice
	       thing), add spaces escaped with backslashes.  The
	       default is ``Login:  ''

	       The string displayed to prompt for a password.  The
	       default is ``Password:  ''

	       The font used to display both prompts.

	       The color used to display both prompts.

	       A message which is displayed when the authentication
	       fails.  The default is ``Login incorrect''

	       The font used to display the failure message.

	       The color used to display the failure message.

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     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	       The number of seconds that the failure message is
	       displayed.  The default is 30.

	       This specifies the translations used for the login
	       widget.	Refer to the X Toolkit documentation for a
	       complete discussion on translations.  The default
	       translation table is:

		    Ctrl<Key>H:	   delete-previous-character() \n\
		    Ctrl<Key>D:	   delete-character() \n\
		    Ctrl<Key>B:	   move-backward-character() \n\
		    Ctrl<Key>F:	   move-forward-character() \n\
		    Ctrl<Key>A:	   move-to-begining() \n\
		    Ctrl<Key>E:	   move-to-end() \n\
		    Ctrl<Key>K:	   erase-to-end-of-line() \n\
		    Ctrl<Key>U:	   erase-line() \n\
		    Ctrl<Key>X:	   erase-line() \n\
		    Ctrl<Key>C:	   restart-session() \n\
		    Ctrl<Key>\\:   abort-session() \n\
		    <Key>BackSpace:delete-previous-character() \n\
		    <Key>Delete:   delete-previous-character() \n\
		    <Key>Return:   finish-field() \n\
		    <Key>:	   insert-char() \

	  The actions which are supported by the widget are:

	       Erases the character before the cursor.

	       Erases the character after the cursor.

	       Moves the cursor backward.

	       Moves the cursor forward.

	       (Apologies about the spelling error.)  Moves the cursor
	       to the beginning of the editable text.

	       Moves the cursor to the end of the editable text.

	       Erases all text after the cursor.


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     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	       Erases the entire text.

	       If the cursor is in the name field, proceeds to the
	       password field; if the cursor is in the password field,
	       checks the current name/password pair.  If the
	       name/password pair is valid, xdm starts the session.
	       Otherwise the failure message is displayed and the user
	       is prompted again.

	       Terminates and restarts the server.

	       Terminates the server, disabling it.  This action is
	       not accessible in the default configuration.  There are
	       various reasons to stop xdm on a system console, such
	       as when shutting the system down, when using xdmshell,
	       to start another type of server, or to generally access
	       the console.  Sending xdm a SIGHUP will restart the
	       display.	 See the section Controlling XDM.

	       Resets the X server and starts a new session.  This can
	       be used when the resources have been changed and you
	       want to test them or when the screen has been
	       overwritten with system messages.

	       Inserts the character typed.

	       Specifies a single word argument which is passed to the
	       session at startup.  See the section Session Program.

	       Disables access control in the server.  This can be
	       used when the .Xauthority file cannot be created by
	       xdm. Be very careful using this; it might be better to
	       disconnect the machine from the network before doing

	  The Xstartup file is typically a shell script.  It is run as
	  root and should be very careful about security.  This is the
	  place to put commands which add entries to /etc/utmp (the
	  sessreg program may be useful here), mount users' home
	  directories from file servers, display the message of the
	  day, or abort the session if logins are not allowed.

	  In addition to any specified by DisplayManager.exportList,
	  the following environment variables are passed:

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     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	       DISPLAY	      the associated display name
	       HOME	      the initial working directory of the user
	       USER	      the user name
	       PATH	      the value of DisplayManager.DISPLAY.systemPath
	       SHELL	      the value of DisplayManager.DISPLAY.systemShell
	       XAUTHORITY     may be set to an authority file

	  No arguments are passed to the script.  Xdm waits until this
	  script exits before starting the user session.  If the exit
	  value of this script is non-zero, xdm discontinues the
	  session and starts another authentication cycle.

	  The sample Xstartup file shown here prevents login while the
	  file /etc/nologin exists. Thus this is not a complete
	  example, but simply a demonstration of the available

	  Here is a sample Xstartup script:

	       # Xstartup
	       # This program is run as root after the user is verified
	       if [ -f /etc/nologin ]; then
		    xmessage -file /etc/nologin
		    exit 1
	       sessreg -a -l $DISPLAY -x /usr/X11R6/lib/xdm/Xservers $USER
	       exit 0

	  The Xsession program is the command which is run as the
	  user's session.  It is run with the permissions of the
	  authorized user.

	  In addition to any specified by DisplayManager.exportList,
	  the following environment variables are passed:

	       DISPLAY	      the associated display name
	       HOME	      the initial working directory of the user
	       USER	      the user name
	       PATH	      the value of DisplayManager.DISPLAY.userPath
	       SHELL	      the user's default shell (from getpwnam)
	       XAUTHORITY     may be set to a non-standard authority file
	       KRB5CCNAME     may be set to a Kerberos credentials cache file

	  At most installations, Xsession should look in $HOME for a

     Page 19					    (printed 12/16/98)

     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	  file .xsession, which contains commands that each user would
	  like to use as a session.  Xsession should also implement a
	  system default session if no user-specified session exists.
	  See the section Typical Usage.

	  An argument may be passed to this program from the
	  authentication widget using the `set-session-argument'
	  action.  This can be used to select different styles of
	  session.  One good use of this feature is to allow the user
	  to escape from the ordinary session when it fails.  This
	  allows users to repair their own .xsession if it fails,
	  without requiring administrative intervention.  The example
	  following demonstrates this feature.

	  This example recognizes the special ``failsafe'' mode,
	  specified in the translations in the Xresources file, to
	  provide an escape from the ordinary session.	It also
	  requires that the .xsession file be executable so we don't
	  have to guess what shell it wants to use.

	       # Xsession
	       # This is the program that is run as the client
	       # for the display manager.

	       case $# in
		    case $1 in
			 exec xterm -geometry 80x24-0-0


	       if [ -f "$startup" ]; then
		    exec "$startup"
		    if [ -f "$resources" ]; then
			 xrdb -load "$resources"
		    twm &
		    xman -geometry +10-10 &
		    exec xterm -geometry 80x24+10+10 -ls

	  The user's .xsession file might look something like this

     Page 20					    (printed 12/16/98)

     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	  example.  Don't forget that the file must have execute
	       #! /bin/csh
	       # no -f in the previous line so .cshrc gets run to set $PATH
	       twm &
	       xrdb -merge "$HOME/.Xresources"
	       emacs -geometry +0+50 &
	       xbiff -geometry -430+5 &
	       xterm -geometry -0+50 -ls

	  Symmetrical with Xstartup, the Xreset script is run after
	  the user session has terminated.  Run as root, it should
	  contain commands that undo the effects of commands in
	  Xstartup, removing entries from /etc/utmp or unmounting
	  directories from file servers.  The environment variables
	  that were passed to Xstartup are also passed to Xreset.

	  A sample Xreset script:
	       # Xreset
	       # This program is run as root after the session ends
	       sessreg -d -l $DISPLAY -x /usr/X11R6/lib/xdm/Xservers $USER
	       exit 0

	  Xdm controls local servers using POSIX signals.  SIGHUP is
	  expected to reset the server, closing all client connections
	  and performing other cleanup duties.	SIGTERM is expected to
	  terminate the server.	 If these signals do not perform the
	  expected actions, the resources
	  DisplayManager.DISPLAY.resetSignal and
	  DisplayManager.DISPLAY.termSignal can specify alternate

	  To control remote terminals not using XDMCP, xdm searches
	  the window hierarchy on the display and uses the protocol
	  request KillClient in an attempt to clean up the terminal
	  for the next session.	 This may not actually kill all of the
	  clients, as only those which have created windows will be
	  noticed.  XDMCP provides a more sure mechanism; when xdm
	  closes its initial connection, the session is over and the
	  terminal is required to close all other connections.

	  Xdm responds to two signals: SIGHUP and SIGTERM.  When sent
	  a SIGHUP, xdm rereads the configuration file, the access
	  control file, and the servers file.  For the servers file,

     Page 21					    (printed 12/16/98)

     XDM(1)		 X Version 11 (Release 6)		XDM(1)

	  it notices if entries have been added or removed.  If a new
	  entry has been added, xdm starts a session on the associated
	  display.  Entries which have been removed are disabled
	  immediately, meaning that any session in progress will be
	  terminated without notice and no new session will be

	  When sent a SIGTERM, xdm terminates all sessions in progress
	  and exits.  This can be used when shutting down the system.

	  Xdm attempts to mark its various sub-processes for ps(1) by
	  editing the command line argument list in place.  Because
	  xdm can't allocate additional space for this task, it is
	  useful to start xdm with a reasonably long command line
	  (using the full path name should be enough).	Each process
	  which is servicing a display is marked -display.

	  You can use xdm to run a single session at a time, using the
	  4.3 init options or other suitable daemon by specifying the
	  server on the command line:

	       xdm -server ":0 SUN-3/60CG4 local /usr/X11R6/bin/X :0"

	  Or, you might have a file server and a collection of X
	  terminals.  The configuration for this is identical to the
	  sample above, except the Xservers file would look like

	       extol:0 VISUAL-19 foreign
	       exalt:0 NCD-19 foreign
	       explode:0 NCR-TOWERVIEW3000 foreign

	  This directs xdm to manage sessions on all three of these
	  terminals.  See the section Controlling Xdm for a
	  description of using signals to enable and disable these
	  terminals in a manner reminiscent of init(8).

	  One thing that xdm isn't very good at doing is coexisting
	  with other window systems.  To use multiple window systems
	  on the same hardware, you'll probably be more interested in

			      the default configuration file

	  $HOME/.Xauthority   user authorization file where xdm stores
			      keys for clients to read

     Page 22					    (printed 12/16/98)

     XDM(1)		 X Version 11 (Release 6)		XDM(1)

			      the default chooser

			      the default resource database loader

	  <XRoot>/bin/X11/X   the default server

			      the default session program and failsafe

			      the default place for authorization

	  /tmp/K5C<display>   Kerberos credentials cache

	  Note: <XRoot> refers to the root of the X11 install tree.

	  X(1), xinit(1), xauth(1), Xsecurity(1), sessreg(1),
	  X Display Manager Control Protocol

	  Keith Packard, MIT X Consortium

     Page 23					    (printed 12/16/98)


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