1XDM(1)                      General Commands Manual                     XDM(1)
2
3
4

NAME

6       xdm - X Display Manager with support for XDMCP, host chooser
7

SYNOPSIS

9       xdm [ -config configuration_file ] [ -nodaemon ] [ -debug debug_level ]
10       [ -error error_log_file  ]  [  -resources  resource_file  ]  [  -server
11       server_entry ] [ -session session_program ]
12

DESCRIPTION

14       Xdm  manages a collection of X displays, which may be on the local host
15       or remote servers.  The design of xdm was guided by the needs of X ter‐
16       minals  as well as The Open Group standard XDMCP, the X Display Manager
17       Control Protocol.  Xdm provides services similar to those  provided  by
18       init,  getty and login on character terminals: prompting for login name
19       and password, authenticating the user, and running a ``session.''
20
21       A ``session'' is defined by the lifetime of a  particular  process;  in
22       the  traditional character-based terminal world, it is the user's login
23       shell.  In the xdm context, it is an arbitrary session  manager.   This
24       is  because  in  a  windowing environment, a user's login shell process
25       does not necessarily have any terminal-like  interface  with  which  to
26       connect.   When  a real session manager is not available, a window man‐
27       ager or terminal emulator is typically used as the ``session manager,''
28       meaning that termination of this process terminates the user's session.
29
30       When  the  session  is terminated, xdm resets the X server and (option‐
31       ally) restarts the whole process.
32
33       When xdm receives an Indirect query via XDMCP, it  can  run  a  chooser
34       process to perform an XDMCP BroadcastQuery (or an XDMCP Query to speci‐
35       fied hosts) on behalf of the display and offer a menu of possible hosts
36       that  offer  XDMCP  display  management.  This feature is useful with X
37       terminals that do not offer a host menu themselves.
38
39       Xdm can be configured to ignore BroadcastQuery messages  from  selected
40       hosts.   This is useful when you don't want the host to appear in menus
41       produced by chooser or X terminals themselves.
42
43       Because xdm provides the first interface that users  will  see,  it  is
44       designed  to  be  simple to use and easy to customize to the needs of a
45       particular site.  Xdm has many options, most of which  have  reasonable
46       defaults.   Browse through the various sections of this manual, picking
47       and choosing the things you want to change.  Pay  particular  attention
48       to  the  Session Program section, which will describe how to set up the
49       style of session desired.
50

OVERVIEW

52       xdm is highly configurable, and most of its behavior can be  controlled
53       by  resource  files  and shell scripts.  The names of these files them‐
54       selves are resources read from the file xdm-config or the file named by
55       the -config option.
56
57       xdm  offers  display  management  two  different ways.  It can manage X
58       servers running on the local machine and specified in Xservers, and  it
59       can  manage  remote  X servers (typically X terminals) using XDMCP (the
60       XDM Control Protocol) as specified in the Xaccess file.
61
62       The resources of the X clients run by xdm outside the  user's  session,
63       including  xdm's own login window, can be affected by setting resources
64       in the Xresources file.
65
66       For X terminals that do not offer a menu of hosts to get  display  man‐
67       agement from, xdm can collect willing hosts and run the chooser program
68       to offer the user a menu.  For X displays attached to a host, this step
69       is typically not used, as the local host does the display management.
70
71       After  resetting  the X server, xdm runs the Xsetup script to assist in
72       setting up the screen the user sees along with the xlogin widget.
73
74       The xlogin widget, which xdm presents, offers the  familiar  login  and
75       password prompts.
76
77       After the user logs in, xdm runs the Xstartup script as root.
78
79       Then  xdm  runs  the  Xsession script as the user.  This system session
80       file may do some additional startup and typically  runs  the  .xsession
81       script  in  the user's home directory.  When the Xsession script exits,
82       the session is over.
83
84       At the end of the session, the Xreset script is run to clean up, the  X
85       server is reset, and the cycle starts over.
86
87       The  file   /var/log/xdm.log  will  contain error messages from xdm and
88       anything output to stderr by  Xsetup,  Xstartup,  Xsession  or  Xreset.
89       When  you  have  trouble getting xdm working, check this file to see if
90       xdm has any clues to the trouble.
91

OPTIONS

93       All of these options, except -config itself, specify  values  that  can
94       also be specified in the configuration file as resources.
95
96       -config configuration_file
97              Names  the configuration file, which specifies resources to con‐
98              trol  the  behavior  of  xdm.   /etc/X11/xdm/xdm-config  is  the
99              default.  See the section Configuration File.
100
101       -nodaemon
102              Specifies  ``false'' as the value for the DisplayManager.daemon‐
103              Mode resource.  This  suppresses  the  normal  daemon  behavior,
104              which  is  for  xdm  to close all file descriptors, disassociate
105              itself from the controlling terminal,  and  put  itself  in  the
106              background when it first starts up.
107
108       -debug debug_level
109              Specifies  the  numeric  value for the DisplayManager.debugLevel
110              resource.  A non-zero value causes xdm to print lots  of  debug‐
111              ging  statements  to the terminal; it also disables the Display‐
112              Manager.daemonMode resource, forcing xdm to  run  synchronously.
113              To interpret these debugging messages, a copy of the source code
114              for xdm is almost a necessity.  No  attempt  has  been  made  to
115              rationalize or standardize the output.
116
117       -error error_log_file
118              Specifies   the   value   for   the  DisplayManager.errorLogFile
119              resource.  This file contains errors from xdm as  well  as  any‐
120              thing  written to stderr by the various scripts and programs run
121              during the progress of the session.
122
123       -resources resource_file
124              Specifies the value for the  DisplayManager*resources  resource.
125              This  file  is  loaded  using  xrdb(1)  to specify configuration
126              parameters for the authentication widget.
127
128       -server server_entry
129              Specifies the value  for  the  DisplayManager.servers  resource.
130              See  the section Local Server Specification for a description of
131              this resource.
132
133       -udpPort port_number
134              Specifies the value for the DisplayManager.requestPort resource.
135              This  sets  the  port-number  which  xdm  will monitor for XDMCP
136              requests.  If set to 0, xdm will not listen for XDMCP or Chooser
137              requests.  As XDMCP uses the registered well-known UDP port 177,
138              this resource should not be changed to a  value  other  than  0,
139              except for debugging.
140
141       -session session_program
142              Specifies  the  value  for  the DisplayManager*session resource.
143              This indicates the program to run as the session after the  user
144              has logged in.
145
146       -xrm resource_specification
147              Allows an arbitrary resource to be specified, as in most X Tool‐
148              kit applications.
149

RESOURCES

151       At many stages the actions of xdm can be controlled through the use  of
152       its  configuration  file,  which  is  in  the  X resource format.  Some
153       resources modify the behavior of xdm on all displays, while others mod‐
154       ify  its  behavior on a single display.  Where actions relate to a spe‐
155       cific display, the display name is  inserted  into  the  resource  name
156       between ``DisplayManager'' and the final resource name segment.
157
158       For  local  displays,  the resource name and class are as read from the
159       Xservers file.
160
161       For remote displays, the resource name is what the network  address  of
162       the display resolves to.  See the removeDomain resource.  The name must
163       match exactly; xdm is not aware of all the network aliases  that  might
164       reach a given display.  If the name resolve fails, the address is used.
165       The resource class is as sent  by  the  display  in  the  XDMCP  Manage
166       request.
167
168       Because  the  resource  manager uses colons to separate the name of the
169       resource from its value and dots to separate resource name  parts,  xdm
170       substitutes  underscores  for  both dots and colons when generating the
171       resource name.  For example, DisplayManager.expo_x_org_0.startup is the
172       name  of  the  resource  which  defines  the startup shell file for the
173       ``expo.x.org:0'' display.
174
175       DisplayManager.servers
176              This resource either  specifies  a  file  name  full  of  server
177              entries,  one  per line (if the value starts with a slash), or a
178              single server entry.  See the section Local Server Specification
179              for the details.
180
181       DisplayManager.requestPort
182              This  indicates the UDP port number which xdm uses to listen for
183              incoming XDMCP requests.  Unless you need to debug  the  system,
184              leave this with its default value of 177.
185
186       DisplayManager.errorLogFile
187              Error output is normally directed at the system console.  To re‐
188              direct it, set this resource to a file name.  A method  to  send
189              these  messages  to syslog should be developed for systems which
190              support it; however, the wide variety  of  interfaces  precludes
191              any  system-independent implementation.  This file also contains
192              any output directed to stderr by the Xsetup, Xstartup,  Xsession
193              and Xreset files, so it will contain descriptions of problems in
194              those scripts as well.
195
196       DisplayManager.debugLevel
197              If the integer value of this  resource  is  greater  than  zero,
198              reams  of  debugging  information will be printed.  It also dis‐
199              ables daemon mode, which would redirect the information into the
200              bit-bucket,  and  allows  non-root users to run xdm, which would
201              normally not be useful.
202
203       DisplayManager.daemonMode
204              Normally, xdm attempts to make  itself  into  a  daemon  process
205              unassociated with any terminal.  This is accomplished by forking
206              and leaving the  parent  process  to  exit,  then  closing  file
207              descriptors  and  releasing  the  controlling terminal.  In some
208              environments this is not desired  (in  particular,  when  debug‐
209              ging).   Setting  this  resource  to ``false'' will disable this
210              feature.
211
212       DisplayManager.pidFile
213              The filename specified will be created to contain an ASCII  rep‐
214              resentation of the process-id of the main xdm process.  Xdm also
215              uses file locking on this file to attempt to eliminate  multiple
216              daemons  running  on the same machine, which would cause quite a
217              bit of havoc.
218
219       DisplayManager.lockPidFile
220              This is the resource which controls whether xdm uses file  lock‐
221              ing  to  keep  multiple  display managers from running amok.  On
222              System V, this uses the lockf library call, while on BSD it uses
223              flock.
224
225       DisplayManager.authDir
226              This  names  a  directory  under  which xdm stores authorization
227              files while initializing the  session.   The  default  value  is
228              /var/lib/xdm.   Can  be overridden for specific displays by Dis‐
229              playManager.DISPLAY.authFile.
230
231       DisplayManager.autoRescan
232              This boolean controls whether  xdm  rescans  the  configuration,
233              servers,  access  control  and authentication keys files after a
234              session terminates and the files have changed.  By default it is
235              ``true.''   You can force xdm to reread these files by sending a
236              SIGHUP to the main process.
237
238       DisplayManager.removeDomainname
239              When computing the display name  for  XDMCP  clients,  the  name
240              resolver  will  typically create a fully qualified host name for
241              the terminal.  As this is sometimes confusing, xdm  will  remove
242              the  domain  name  portion of the host name if it is the same as
243              the domain name of the local host when this variable is set.  By
244              default the value is ``true.''
245
246       DisplayManager.keyFile
247              XDM-AUTHENTICATION-1  style XDMCP authentication requires that a
248              private key be  shared  between  xdm  and  the  terminal.   This
249              resource specifies the file containing those values.  Each entry
250              in the file consists of a display name and the shared  key.   By
251              default,  xdm does not include support for XDM-AUTHENTICATION-1,
252              as it requires DES which is not generally distributable  because
253              of United States export restrictions.
254
255       DisplayManager.accessFile
256              To prevent unauthorized XDMCP service and to allow forwarding of
257              XDMCP IndirectQuery requests, this file contains a  database  of
258              hostnames  which  are  either  allowed  direct  access  to  this
259              machine, or have a list of hosts to which queries should be for‐
260              warded  to.  The format of this file is described in the section
261              XDMCP Access Control.
262
263       DisplayManager.exportList
264              A list of additional environment variables, separated  by  white
265              space,  to pass on to the Xsetup, Xstartup, Xsession, and Xreset
266              programs.
267
268       DisplayManager.randomFile
269              A file to checksum to generate the seed of  authorization  keys.
270              This  should  be a file that changes frequently.  The default is
271              /dev/mem.
272
273       DisplayManager.randomDevice
274              A file to read 8 bytes from to generate the seed  of  authoriza‐
275              tion  keys.   The default is  /dev/urandom . If this file cannot
276              be read, or if a read blocks for more than 5 seconds, xdm  falls
277              back  to using a checksum of DisplayManager.randomFile to gener‐
278              ate the seed.
279
280       DisplayManager.prngdSocket
281
282       DisplayManager.prngPort
283              A UNIX domain socket name or a TCP socket port number  on  local
284              host  on which a Pseudo-Random Number Generator Daemon, like EGD
285              (http://egd.sourceforge.net) is listening, in order to  generate
286              the  autorization keys. Either a non null port or a valid socket
287              name must be specified. The default is to  use  the  Unix-domain
288              socket /tmp/entropy.
289
290       On systems that don't have such a daemon, a fall-back entropy gathering
291       system, based on various log file contents hashed by the MD5  algorithm
292       is used instead.
293
294       DisplayManager.greeterLib
295              On  systems that support a dynamically-loadable greeter library,
296              the name of the library.  The default is
297               /usr/libexec/libXdmGreet.so.
298
299       DisplayManager.choiceTimeout
300              Number of seconds to wait for display to respond after user  has
301              selected a host from the chooser.  If the display sends an XDMCP
302              IndirectQuery within this time, the request is forwarded to  the
303              chosen  host.  Otherwise, it is assumed to be from a new session
304              and the chooser is offered again.  Default is 15.
305
306       DisplayManager.sourceAddress
307              Use the numeric IP address of the incoming connection on  multi‐
308              homed hosts instead of the host name. This is to avoid trying to
309              connect on the wrong interface which might be down at this time.
310
311       DisplayManager.willing
312              This specifies a program which is run (as) root when an an XDMCP
313              BroadcastQuery  is received and this host is configured to offer
314              XDMCP display management. The output of this program may be dis‐
315              played  on  a  chooser  window.  If no program is specified, the
316              string Willing to manage is sent.
317
318       DisplayManager.DISPLAY.resources
319              This resource specifies the name of the file  to  be  loaded  by
320              xrdb  as  the resource database onto the root window of screen 0
321              of the display.  The  Xsetup  program,  the  Login  widget,  and
322              chooser  will use the resources set in this file.  This resource
323              data base is loaded just before the authentication procedure  is
324              started,  so  it can control the appearance of the login window.
325              See the section Authentication Widget, which describes the vari‐
326              ous resources that are appropriate to place in this file.  There
327              is no default value for this resource, but
328               /etc/X11/xdm/Xresources is the conventional name.
329
330       DisplayManager.DISPLAY.chooser
331              Specifies the program run to offer  a  host  menu  for  Indirect
332              queries redirected to the special host name CHOOSER.
333               /usr/libexec/chooser   is  the default.  See the sections XDMCP
334              Access Control and Chooser.
335
336       DisplayManager.DISPLAY.xrdb
337              Specifies the program used to load the resources.   By  default,
338              xdm uses  /usr/bin/xrdb.
339
340       DisplayManager.DISPLAY.cpp
341              This  specifies  the name of the C preprocessor which is used by
342              xrdb.
343
344       DisplayManager.DISPLAY.setup
345              This specifies a program which is run (as root) before  offering
346              the  Login window.  This may be used to change the appearance of
347              the screen around the Login window or to put  up  other  windows
348              (e.g.,  you may want to run xconsole here).  By default, no pro‐
349              gram is run.  The conventional name for  a  file  used  here  is
350              Xsetup.  See the section Setup Program.
351
352       DisplayManager.DISPLAY.startup
353              This  specifies  a  program  which  is  run  (as root) after the
354              authentication process succeeds.  By default, no program is run.
355              The conventional name for a file used here is Xstartup.  See the
356              section Startup Program.
357
358       DisplayManager.DISPLAY.session
359              This specifies the session to be executed (not running as root).
360              By  default,   /usr/bin/xterm  is run.  The conventional name is
361              Xsession.  See the section Session Program.
362
363       DisplayManager.DISPLAY.reset
364              This specifies a program which is run (as root) after  the  ses‐
365              sion  terminates.   By  default, no program is run.  The conven‐
366              tional name is Xreset.  See the section Reset Program.
367
368       DisplayManager.DISPLAY.openDelay
369
370       DisplayManager.DISPLAY.openRepeat
371
372       DisplayManager.DISPLAY.openTimeout
373
374       DisplayManager.DISPLAY.startAttempts
375
376       DisplayManager.DISPLAY.reservAttempts
377              These  numeric  resources  control  the  behavior  of  xdm  when
378              attempting  to  open  intransigent  servers.   openDelay  is the
379              length of the pause  in  seconds  between  successive  attempts,
380              openRepeat is the number of attempts to make, openTimeout is the
381              amount of time to wait while actually attempting the open (i.e.,
382              the  maximum time spent in the connect(2) system call) and star‐
383              tAttempts is the number of times this  entire  process  is  done
384              before  giving up on the server.  After openRepeat attempts have
385              been made, or if openTimeout seconds elapse  in  any  particular
386              attempt,  xdm  terminates and restarts the server, attempting to
387              connect again.  This process is repeated startAttempts times, at
388              which point the display is declared dead and disabled.  Although
389              this behavior may seem arbitrary, it has been empirically devel‐
390              oped  and works quite well on most systems.  The bound reservAt‐
391              tempts is the number of times a successful connect is allowed to
392              be followed by a fatal error.  When reached, the display is dis‐
393              abled.  The default values are  openDelay:  15,  openRepeat:  5,
394              openTimeout: 120, startAttempts: 4 and reservAttempts: 2.
395
396       DisplayManager.DISPLAY.pingInterval
397
398       DisplayManager.DISPLAY.pingTimeout
399              To  discover  when  remote  displays disappear, xdm occasionally
400              pings them, using an X connection and XSync calls.  pingInterval
401              specifies the time (in minutes) between each ping attempt, ping‐
402              Timeout specifies the maximum amount of  time  (in  minutes)  to
403              wait  for the terminal to respond to the request.  If the termi‐
404              nal does not respond, the session is declared  dead  and  termi‐
405              nated.   By  default,  both  are  set to 5 minutes.  If you fre‐
406              quently use X terminals which can become isolated from the  man‐
407              aging host, you may wish to increase this value.  The only worry
408              is that sessions will continue to exist after the  terminal  has
409              been  accidentally  disabled.  xdm will not ping local displays.
410              Although it would seem harmless, it is unpleasant when the work‐
411              station  session is terminated as a result of the server hanging
412              for NFS service and not responding to the ping.
413
414       DisplayManager.DISPLAY.terminateServer
415              This boolean resource specifies whether the X server  should  be
416              terminated  when a session terminates (instead of resetting it).
417              This option can be used when the server tends  to  grow  without
418              bound over time, in order to limit the amount of time the server
419              is run.  The default value is ``false.''
420
421       DisplayManager.DISPLAY.userPath
422              Xdm sets the PATH environment variable for the session  to  this
423              value.   It should be a colon separated list of directories; see
424              sh(1)  for  a  full   description.    The   default   value   is
425              ``/bin:/usr/bin:/usr/bin:/usr/ucb''.
426
427       DisplayManager.DISPLAY.systemPath
428              Xdm sets the PATH environment variable for the startup and reset
429              scripts to the value of this resource.   The  default  for  this
430              resource  is ``/etc:/bin:/usr/bin:/usr/bin:/usr/ucb''.  Note the
431              absence of ``.'' from this entry.  This is a  good  practice  to
432              follow for root; it avoids many common Trojan Horse system pene‐
433              tration schemes.
434
435       DisplayManager.DISPLAY.systemShell
436              Xdm sets the SHELL environment  variable  for  the  startup  and
437              reset  scripts  to the value of this resource.  It is /bin/sh by
438              default.
439
440       DisplayManager.DISPLAY.failsafeClient
441              If the default session fails to execute, xdm will fall  back  to
442              this  program.   This program is executed with no arguments, but
443              executes using the same environment  variables  as  the  session
444              would  have  had (see the section Session Program).  By default,
445              /usr/bin/xterm is used.
446
447       DisplayManager.DISPLAY.grabServer
448
449       DisplayManager.DISPLAY.grabTimeout
450              To improve security, xdm grabs the  server  and  keyboard  while
451              reading  the  login  name and password.  The grabServer resource
452              specifies if the server should be held for the duration  of  the
453              name/password  reading.  When ``false,'' the server is ungrabbed
454              after the  keyboard  grab  succeeds,  otherwise  the  server  is
455              grabbed  until  just  before the session begins.  The default is
456              ``false.''  The grabTimeout resource specifies the maximum  time
457              xdm  will  wait  for  the grab to succeed.  The grab may fail if
458              some other client has the server grabbed,  or  possibly  if  the
459              network  latencies  are  very high.  This resource has a default
460              value of 3 seconds; you should be cautious when raising it, as a
461              user  can  be spoofed by a look-alike window on the display.  If
462              the grab fails, xdm kills and restarts the server (if  possible)
463              and the session.
464
465       DisplayManager.DISPLAY.authorize
466
467       DisplayManager.DISPLAY.authName
468              authorize  is a boolean resource which controls whether xdm gen‐
469              erates and uses authorization for the local server  connections.
470              If  authorization  is  used, authName is a list of authorization
471              mechanisms to use, separated by white space.  XDMCP  connections
472              dynamically  specify  which  authorization  mechanisms  are sup‐
473              ported, so authName is ignored in this case.  When authorize  is
474              set  for  a display and authorization is not available, the user
475              is informed by having a different message displayed in the login
476              widget.   By default, authorize is ``true,''  authName is ``MIT-
477              MAGIC-COOKIE-1,''  or,  if  XDM-AUTHORIZATION-1  is   available,
478              ``XDM-AUTHORIZATION-1 MIT-MAGIC-COOKIE-1.''
479
480       DisplayManager.DISPLAY.authFile
481              This file is used to communicate the authorization data from xdm
482              to the server, using the -auth server command line  option.   It
483              should  be kept in a directory which is not world-writable as it
484              could easily be removed, disabling the  authorization  mechanism
485              in  the server.  If not specified, a name is generated from Dis‐
486              playManager.authDir and the name of the display.
487
488       DisplayManager.DISPLAY.authComplain
489              If set to ``false,'' disables the use of the unsecureGreeting in
490              the  login  window.  See the section Authentication Widget.  The
491              default is ``true.''
492
493       DisplayManager.DISPLAY.resetSignal
494              The number of the signal xdm sends to reset the server.  See the
495              section Controlling the Server.  The default is 1 (SIGHUP).
496
497       DisplayManager.DISPLAY.termSignal
498              The number of the signal xdm sends to terminate the server.  See
499              the  section  Controlling  the  Server.   The  default   is   15
500              (SIGTERM).
501
502       DisplayManager.DISPLAY.resetForAuth
503              The  original  implementation  of  authorization  in  the sample
504              server reread the  authorization  file  at  server  reset  time,
505              instead  of when checking the initial connection.  As xdm gener‐
506              ates the authorization information just before connecting to the
507              display,  an  old  server would not get up-to-date authorization
508              information.  This resource causes xdm to  send  SIGHUP  to  the
509              server  after  setting up the file, causing an additional server
510              reset to occur, during which time the new authorization informa‐
511              tion  will  be  read.  The default is ``false,'' which will work
512              for all MIT servers.
513
514       DisplayManager.DISPLAY.userAuthDir
515              When xdm is unable to write to the usual user authorization file
516              ($HOME/.Xauthority),  it  creates  a  unique  file  name in this
517              directory and points the environment variable XAUTHORITY at  the
518              created file.  It uses /tmp by default.
519

CONFIGURATION FILE

521       First,  the  xdm configuration file should be set up.  Make a directory
522       (usually  /etc/X11/xdm) to contain all of the relevant files.
523
524       Here is a reasonable configuration file, which could be named  xdm-con‐
525       fig:
526
527
528            DisplayManager.servers:            /etc/X11/xdm/Xservers
529            DisplayManager.errorLogFile:       /var/log/xdm.log
530            DisplayManager*resources:          /etc/X11/xdm/Xresources
531            DisplayManager*startup:            /etc/X11/xdm/Xstartup
532            DisplayManager*session:            /etc/X11/xdm/Xsession
533            DisplayManager.pidFile:            /var/run/xdm-pid
534            DisplayManager._0.authorize:       true
535            DisplayManager*authorize:          false
536
537
538       Note  that  this  file mostly contains references to other files.  Note
539       also that some of the resources are specified with ``*'' separating the
540       components.  These resources can be made unique for each different dis‐
541       play, by replacing the ``*'' with the display-name, but  normally  this
542       is  not  very useful.  See the Resources section for a complete discus‐
543       sion.
544

XDMCP ACCESS CONTROL

546       The database file specified by the  DisplayManager.accessFile  provides
547       information  which  xdm uses to control access from displays requesting
548       XDMCP service.  This file contains three  types  of  entries:   entries
549       which  control  the  response  to Direct and Broadcast queries, entries
550       which control the response to Indirect queries, and macro definitions.
551
552       The format of the Direct entries is simple, either a  host  name  or  a
553       pattern,  which  is  distinguished from a host name by the inclusion of
554       one or more meta characters (`*' matches any  sequence  of  0  or  more
555       characters,  and  `?'  matches any single character) which are compared
556       against the host name of the display device.  If the entry  is  a  host
557       name,  all  comparisons  are  done using network addresses, so any name
558       which converts to the correct network address may be  used.   For  pat‐
559       terns,  only canonical host names are used in the comparison, so ensure
560       that you do not attempt to match aliases.  Preceding either a host name
561       or  a  pattern with a `!' character causes hosts which match that entry
562       to be excluded.
563
564       To only respond to Direct queries for a host or pattern, it can be fol‐
565       lowed  by  the  optional  ``NOBROADCAST'' keyword.  This can be used to
566       prevent an xdm server  from  appearing  on  menus  based  on  Broadcast
567       queries.
568
569       An  Indirect entry also contains a host name or pattern, but follows it
570       with a list of host names or macros to which indirect queries should be
571       sent.
572
573       A  macro  definition contains a macro name and a list of host names and
574       other macros that the macro expands to.   To  distinguish  macros  from
575       hostnames,  macro  names  start  with  a  `%' character.  Macros may be
576       nested.
577
578       Indirect entries may also specify to have xdm run chooser  to  offer  a
579       menu of hosts to connect to.  See the section Chooser.
580
581       When  checking  access  for  a  particular  display host, each entry is
582       scanned in turn and the first matching entry determines  the  response.
583       Direct  and Broadcast entries are ignored when scanning for an Indirect
584       entry and vice-versa.
585
586       Blank lines are ignored, `#' is treated as a comment delimiter  causing
587       the  rest of that line to be ignored, and `\newline' causes the newline
588       to be ignored, allowing indirect host lists to span multiple lines.
589
590       Here is an example Xaccess file:
591
592       #
593       # Xaccess - XDMCP access control file
594       #
595
596       #
597       # Direct/Broadcast query entries
598       #
599
600       !xtra.lcs.mit.edu   # disallow direct/broadcast service for xtra
601       bambi.ogi.edu       # allow access from this particular display
602       *.lcs.mit.edu       # allow access from any display in LCS
603
604       *.deshaw.com        NOBROADCAST         # allow only direct access
605       *.gw.com                                # allow direct and broadcast
606
607       #
608       # Indirect query entries
609       #
610
611       %HOSTS              expo.lcs.mit.edu xenon.lcs.mit.edu \
612                           excess.lcs.mit.edu kanga.lcs.mit.edu
613
614       extract.lcs.mit.edu xenon.lcs.mit.edu   #force extract to contact xenon
615       !xtra.lcs.mit.edu   dummy               #disallow indirect access
616       *.lcs.mit.edu       %HOSTS              #all others get to choose
617
618       If compiled with IPv6 support, multicast address  groups  may  also  be
619       included  in the list of addresses indirect queries are set to.  Multi‐
620       cast addresses may be followed by  an  optional  /  character  and  hop
621       count.  If  no hop count is specified, the multicast hop count defaults
622       to 1, keeping the packet on the local network. For  IPv4  multicasting,
623       the hop count is used as the TTL.
624
625       Examples:
626
627       rincewind.sample.net ff02::1                 #IPv6 Multicast to ff02::1
628                                                    #with a hop count of 1
629       ponder.sample.net    CHOOSER 239.192.1.1/16  #Offer a menu of hosts
630                                                    #who respond to IPv4 Multicast
631                                                    # to 239.192.1.1 with a TTL of 16
632

CHOOSER

634       For X terminals that do not offer a host menu for use with Broadcast or
635       Indirect queries, the chooser program can do this  for  them.   In  the
636       Xaccess  file,  specify  ``CHOOSER'' as the first entry in the Indirect
637       host list.  Chooser will send a Query request to each of the  remaining
638       host names in the list and offer a menu of all the hosts that respond.
639
640       The  list  may consist of the word ``BROADCAST,'' in which case chooser
641       will send a Broadcast instead, again offering a menu of all hosts  that
642       respond.   Note  that  on some operating systems, UDP packets cannot be
643       broadcast, so this feature will not work.
644
645       Example Xaccess file using chooser:
646
647       extract.lcs.mit.edu  CHOOSER %HOSTS          #offer a menu of these hosts
648       xtra.lcs.mit.edu     CHOOSER BROADCAST       #offer a menu of all hosts
649
650       The program to use for chooser is specified by the  DisplayManager.DIS‐
651       PLAY.chooser  resource.  For more flexibility at this step, the chooser
652       could be a shell script.  Chooser is the session manager  here;  it  is
653       run instead of a child xdm to manage the display.
654
655       Resources  for  this program can be put into the file named by Display‐
656       Manager.DISPLAY.resources.
657
658       When the user selects a host, chooser prints the host chosen, which  is
659       read  by the parent xdm, and exits.  xdm closes its connection to the X
660       server, and the server resets and sends another Indirect XDMCP request.
661       xdm  remembers the user's choice (for DisplayManager.choiceTimeout sec‐
662       onds) and forwards the request to the chosen host, which starts a  ses‐
663       sion on that display.
664

LISTEN

666       The  following  configuration directive is also defined for the Xaccess
667       configuration file:
668
669       LISTEN interface [list of multicast group addresses]
670              interface may be a hostname or IP address representing a network
671              interface  on  this  machine, or the wildcard * to represent all
672              available network interfaces.
673
674       If one or more LISTEN lines are specified, xdm only listens  for  XDMCP
675       connections  on  the specified interfaces. If multicast group addresses
676       are listed on a listen line, xdm joins  the  multicast  groups  on  the
677       given interface.
678
679       If no LISTEN lines are given, the original behavior of listening on all
680       interfaces is preserved for backwards compatibility.  Additionally,  if
681       no  LISTEN  is  specified,  xdm  joins the default XDMCP IPv6 multicast
682       group, when compiled with IPv6 support.
683
684       To disable listening for XDMCP connections altogther, a line of  LISTEN
685       with  no addresses may be specified, or the previously supported method
686       of setting DisplayManager.requestPort to 0 may be used.
687
688       Examples:
689       LISTEN * ff02::1    # Listen on all interfaces and to the
690                           # ff02::1 IPv6 multicast group.
691       LISTEN 10.11.12.13  # Listen only on this interface, as long
692                           # as no other listen directives appear in
693                           # file.
694

IPv6 MULTICAST ADDRESS SPECIFICATION

696       The   Internet   Assigned   Numbers   Authority   has   has    assigned
697       ff0X:0:0:0:0:0:0:12b  as  the  permanently  assigned range of multicast
698       addresses for XDMCP. The X in the prefix may be replaced by  any  valid
699       scope  identifier,  such  as 1 for Interface-Local, 2 for Link-Local, 5
700       for Site-Local, and so on.  (See IETF RFC 4291 or its  replacement  for
701       further  details  and scope definitions.)  xdm defaults to listening on
702       the Link-Local scope address ff02:0:0:0:0:0:0:12b to most closely match
703       the old IPv4 subnet broadcast behavior.
704

LOCAL SERVER SPECIFICATION

706       The resource DisplayManager.servers gives a server specification or, if
707       the values starts with a slash (/),  the  name  of  a  file  containing
708       server specifications, one per line.
709
710       Each  specification indicates a display which should constantly be man‐
711       aged and which is not using XDMCP.  This method is used  typically  for
712       local  servers only.  If the resource or the file named by the resource
713       is empty, xdm will offer XDMCP service only.
714
715       Each specification consists of at least three parts:  a display name, a
716       display  class,  a display type, and (for local servers) a command line
717       to start the server.  A typical entry for local display number 0  would
718       be:
719
720         :0 Digital-QV local /usr/bin/X :0
721
722       The display types are:
723
724       local     local display: xdm must run the server
725       foreign   remote display: xdm opens an X connection to a running server
726
727
728       The  display  name must be something that can be passed in the -display
729       option to an X program.  This string is used to generate  the  display-
730       specific  resource  names,  so be careful to match the names (e.g., use
731       ``:0 Sun-CG3 local /usr/bin/X :0''  instead  of  ``localhost:0  Sun-CG3
732       local  /usr/bin/X  :0'' if your other resources are specified as ``Dis‐
733       playManager._0.session'').  The display class portion is also  used  in
734       the  display-specific resources, as the class of the resource.  This is
735       useful if you have a large collection of similar displays  (such  as  a
736       corral  of  X  terminals) and would like to set resources for groups of
737       them.  When using XDMCP, the display is required to specify the display
738       class, so the manual for your particular X terminal should document the
739       display class string for your device.  If it doesn't, you can  run  xdm
740       in  debug  mode and look at the resource strings which it generates for
741       that device, which will include the class string.
742
743       When xdm starts a session,  it  sets  up  authorization  data  for  the
744       server.   For  local  servers,  xdm  passes  ``-auth  filename'' on the
745       server's command line to point it at its authorization data.  For XDMCP
746       servers, xdm passes the authorization data to the server via the Accept
747       XDMCP request.
748

RESOURCES FILE

750       The Xresources file is loaded onto the display as a  resource  database
751       using  xrdb.   As  the authentication widget reads this database before
752       starting up, it usually contains parameters for that widget:
753
754            xlogin*login.translations: #override\
755                 Ctrl<Key>R: abort-display()\n\
756                 <Key>F1: set-session-argument(failsafe) finish-field()\n\
757                 <Key>Return: set-session-argument() finish-field()
758            xlogin*borderWidth: 3
759            xlogin*greeting: CLIENTHOST
760            #ifdef COLOR
761            xlogin*greetColor: CadetBlue
762            xlogin*failColor: red
763            #endif
764
765
766       Please note the translations entry; it specifies a few new translations
767       for  the  widget  which  allow users to escape from the default session
768       (and avoid troubles that may occur in it).  Note that if  #override  is
769       not specified, the default translations are removed and replaced by the
770       new value, not a very useful result as some of the default translations
771       are  quite  useful (such as ``<Key>: insert-char ()'' which responds to
772       normal typing).
773
774       This file may also contain resources for the setup program and chooser.
775

SETUP PROGRAM

777       The Xsetup file is run after the server is reset, but before the  Login
778       window is offered.  The file is typically a shell script.  It is run as
779       root, so should be careful about security.  This is the place to change
780       the root background or bring up other windows that should appear on the
781       screen along with the Login widget.
782
783       In addition to any specified by DisplayManager.exportList, the  follow‐
784       ing environment variables are passed:
785
786            DISPLAY        the associated display name
787            PATH           the value of DisplayManager.DISPLAY.systemPath
788            SHELL          the value of DisplayManager.DISPLAY.systemShell
789            XAUTHORITY     may be set to an authority file
790
791       Note  that  since xdm grabs the keyboard, any other windows will not be
792       able to receive keyboard input.  They will be able to interact with the
793       mouse,  however;  beware of potential security holes here.  If Display‐
794       Manager.DISPLAY.grabServer is set, Xsetup will not be able  to  connect
795       to  the display at all.  Resources for this program can be put into the
796       file named by DisplayManager.DISPLAY.resources.
797
798       Here is a sample Xsetup script:
799
800            #!/bin/sh
801            # Xsetup_0 - setup script for one workstation
802            xcmsdb < /etc/X11/xdm/monitors/alex.0
803            xconsole -geometry 480x130-0-0 -notify -verbose -exitOnFail &
804
805

AUTHENTICATION WIDGET

807       The authentication widget prompts the user for the username,  password,
808       and/or  other  required  authentication data from the keyboard.  Nearly
809       every  imaginable  parameter  can  be  controlled  with   a   resource.
810       Resources for this widget should be put into the file named by Display‐
811       Manager.DISPLAY.resources.  All of these have reasonable  default  val‐
812       ues, so it is not necessary to specify any of them.
813
814       The  resource  file  is loaded with xrdb(1) so it may use the substitu‐
815       tions defined by that program such as CLIENTHOST for the  client  host‐
816       name in the login message, or C pre-processor #ifdef statements to pro‐
817       duce different displays depending on color depth or other variables.
818
819       Xdm can be compiled with support for the Xft(3) library for  font  ren‐
820       dering.    If  this  support is present, font faces are specified using
821       the resources with names ending in ``face'' in the fontconfig face for‐
822       mat described in the Font Names section of fonts.conf(5).  If not, then
823       fonts are specified using the resources with names ending  in  ``font''
824       in  the  traditional X Logical Font Description format described in the
825       Font Names section of X(7).
826
827       xlogin.Login.width, xlogin.Login.height, xlogin.Login.x, xlogin.Login.y
828              The geometry of the Login widget is normally computed  automati‐
829              cally.   If  you  wish to position it elsewhere, specify each of
830              these resources.
831
832       xlogin.Login.foreground
833              The color used to display the input typed by the user.
834
835       xlogin.Login.face
836              The face used to display the input typed by the user when  built
837              with Xft support.  The default is ``Serif-18''.
838
839       xlogin.Login.font
840              The  font  used  to display the input typed by the user when not
841              built with Xft support.
842
843       xlogin.Login.greeting
844              A string which identifies this window.  The default is ``X  Win‐
845              dow System.''
846
847       xlogin.Login.unsecureGreeting
848              When  X authorization is requested in the configuration file for
849              this display and none is in  use,  this  greeting  replaces  the
850              standard  greeting.   The  default is ``This is an unsecure ses‐
851              sion''
852
853       xlogin.Login.greetFace
854              The face used to display the greeting when built with  Xft  sup‐
855              port.  The default is ``Serif-24:italic''.
856
857       xlogin.Login.greetFont
858              The  font  used  to display the greeting when not built with Xft
859              support.
860
861       xlogin.Login.greetColor
862              The color used to display the greeting.
863
864       xlogin.Login.namePrompt
865              The string displayed to prompt for a  user  name.   Xrdb  strips
866              trailing  white  space from resource values, so to add spaces at
867              the end of the prompt (usually a nice thing), add spaces escaped
868              with backslashes.  The default is ``Login:  ''
869
870       xlogin.Login.passwdPrompt
871              The string displayed to prompt for a password, when not using an
872              authentication system such as PAM that provides its own prompts.
873              The default is ``Password:  ''
874
875       xlogin.Login.promptFace
876              The  face  used  to display prompts when built with Xft support.
877              The default is ``Serif-18:bold''.
878
879       xlogin.Login.promptFont
880              The font used to display prompts when not built  with  Xft  sup‐
881              port.
882
883       xlogin.Login.promptColor
884              The color used to display prompts.
885
886       xlogin.Login.changePasswdMessage
887              A  message  which  is  displayed  when  the  users  password has
888              expired.  The default is ``Password Change Required''
889
890       xlogin.Login.fail
891              A message which is displayed when the authentication fails, when
892              not using an authentication system such as PAM that provides its
893              own prompts.  The default is ``Login incorrect''
894
895       xlogin.Login.failFace
896              The face used to display the failure message when built with Xft
897              support.  The default is ``Serif-18:bold''.
898
899       xlogin.Login.failFont
900              The font used to display the failure message when not built with
901              Xft support.
902
903       xlogin.Login.failColor
904              The color used to display the failure message.
905
906       xlogin.Login.failTimeout
907              The number of seconds that the  failure  message  is  displayed.
908              The default is 10.
909
910       xlogin.Login.logoFileName
911              Name  of  an XPM format pixmap to display in the greeter window,
912              if built with XPM support.   The default is no pixmap.
913
914       xlogin.Login.logoPadding
915              Number of pixels of space between the logo pixmap and other ele‐
916              ments  of  the  greeter window, if the pixmap is displayed.  The
917              default is 5.
918
919       xlogin.Login.useShape
920              If set to ``true'', when built with XPM support, attempt to  use
921              the  X  Non-Rectangular Window Shape Extension to set the window
922              shape.  The default is ``true''.
923
924       xlogin.Login.hiColor, xlogin.Login.shdColor
925              Raised appearance bezels may be drawn around the  greeter  frame
926              and text input boxes by setting these resources.  hiColor is the
927              highlight color, used on the top and left sides  of  the  frame,
928              and  the  bottom and right sides of text input areas.   shdColor
929              is the shadow color, used on the bottom and right sides  of  the
930              frame,  and  the  top  and  left sides of text input areas.  The
931              default for both is  the  foreground  color,  providing  a  flat
932              appearance.
933
934       xlogin.Login.frameWidth
935              frameWidth is the width in pixels of the area around the greeter
936              frame drawn in hiColor and shdColor.
937
938       xlogin.Login.innerFramesWidth
939              innerFramesWidth is the width in pixels of the area around  text
940              input areas drawn in hiColor and shdColor.
941
942       xlogin.Login.sepWidth
943              sepWidth  is the width in pixels of the bezeled line between the
944              greeting and input areas drawn in hiColor and shdColor.
945
946       xlogin.Login.allowRootLogin
947              If set to ``false'', don't allow root (and any other  user  with
948              uid  =  0)  to  log in directly.  The default is ``true''.  This
949              setting is only checked by some of the  authentication  backends
950              at this time.
951
952       xlogin.Login.allowNullPasswd
953              If set to ``true'', allow an otherwise failing password match to
954              succeed if the account does not require a password at all.   The
955              default is ``false'', so only users that have passwords assigned
956              can log in.
957
958       xlogin.Login.echoPasswd
959              If set to ``true'',  a  placeholder  character  (echoPasswdChar)
960              will be shown for fields normally set to not echo, such as pass‐
961              word input.  The default is ``false''.
962
963       xlogin.Login.echoPasswdChar
964              Character to display if echoPasswd  is  true.   The  default  is
965              ``*''.   If  set  to an empty value, the cursor will advance for
966              each character input, but no text will be drawn.
967
968       xlogin.Login.translations
969              This specifies the  translations  used  for  the  login  widget.
970              Refer  to  the X Toolkit documentation for a complete discussion
971              on translations.  The default translation table is:
972
973                   Ctrl<Key>H:    delete-previous-character() \n\
974                   Ctrl<Key>D:    delete-character() \n\
975                   Ctrl<Key>B:    move-backward-character() \n\
976                   Ctrl<Key>F:    move-forward-character() \n\
977                   Ctrl<Key>A:    move-to-begining() \n\
978                   Ctrl<Key>E:    move-to-end() \n\
979                   Ctrl<Key>K:    erase-to-end-of-line() \n\
980                   Ctrl<Key>U:    erase-line() \n\
981                   Ctrl<Key>X:    erase-line() \n\
982                   Ctrl<Key>C:    restart-session() \n\
983                   Ctrl<Key>\\:   abort-session() \n\
984                   <Key>BackSpace:delete-previous-character() \n\
985                   <Key>Delete:   delete-previous-character() \n\
986                   <Key>Return:   finish-field() \n\
987                   <Key>:         insert-char() \
988
989
990       The actions which are supported by the widget are:
991
992       delete-previous-character
993              Erases the character before the cursor.
994
995       delete-character
996              Erases the character after the cursor.
997
998       move-backward-character
999              Moves the cursor backward.
1000
1001       move-forward-character
1002              Moves the cursor forward.
1003
1004       move-to-begining
1005              (Apologies about the spelling error.)  Moves the cursor  to  the
1006              beginning of the editable text.
1007
1008       move-to-end
1009              Moves the cursor to the end of the editable text.
1010
1011       erase-to-end-of-line
1012              Erases all text after the cursor.
1013
1014       erase-line
1015              Erases the entire text.
1016
1017       finish-field
1018              If  the  cursor  is  in the name field, proceeds to the password
1019              field; if the cursor is in the password field, checks  the  cur‐
1020              rent  name/password  pair.   If the name/password pair is valid,
1021              xdm starts the session.  Otherwise the failure message  is  dis‐
1022              played and the user is prompted again.
1023
1024       abort-session
1025              Terminates and restarts the server.
1026
1027       abort-display
1028              Terminates  the server, disabling it.  This action is not acces‐
1029              sible in the default configuration.  There are  various  reasons
1030              to  stop xdm on a system console, such as when shutting the sys‐
1031              tem down, when using xdmshell, to start another type of  server,
1032              or  to  generally access the console.  Sending xdm a SIGHUP will
1033              restart the display.  See the section Controlling XDM.
1034
1035       restart-session
1036              Resets the X server and starts a new session.  This can be  used
1037              when  the  resources have been changed and you want to test them
1038              or when the screen has been overwritten with system messages.
1039
1040       insert-char
1041              Inserts the character typed.
1042
1043       set-session-argument
1044              Specifies a single word argument which is passed to the  session
1045              at startup.  See the section Session Program.
1046
1047       allow-all-access
1048              Disables  access  control  in the server.  This can be used when
1049              the .Xauthority file cannot be created by xdm.  Be very  careful
1050              using  this;  it  might be better to disconnect the machine from
1051              the network before doing this.
1052
1053       On  some  systems  (OpenBSD)  the  user's  shell  must  be  listed   in
1054       /etc/shells to allow login through xdm. The normal password and account
1055       expiration dates are enforced too.
1056

STARTUP PROGRAM

1058       The Xstartup program is run as root when the user logs in.  It is typi‐
1059       cally a shell script.  Since it is run as root, Xstartup should be very
1060       careful about security.  This is the place to put  commands  which  add
1061       entries  to  utmp  or  wtmp  files,  (the sessreg program may be useful
1062       here), mount users' home directories from file servers,  or  abort  the
1063       session if logins are not allowed.
1064
1065       In  addition to any specified by DisplayManager.exportList, the follow‐
1066       ing environment variables are passed:
1067
1068            DISPLAY        the associated display name
1069            HOME           the initial working directory of the user
1070            LOGNAME        the user name
1071            USER           the user name
1072            PATH           the value of DisplayManager.DISPLAY.systemPath
1073            SHELL          the value of DisplayManager.DISPLAY.systemShell
1074            XAUTHORITY     may be set to an authority file
1075            WINDOWPATH     may be set to the "window path" leading to the X server
1076
1077
1078       No arguments are passed to the script.  Xdm  waits  until  this  script
1079       exits  before  starting  the  user  session.  If the exit value of this
1080       script is non-zero, xdm discontinues the  session  and  starts  another
1081       authentication cycle.
1082
1083       The  sample  Xstartup  file  shown  here  prevents login while the file
1084       /etc/nologin exists.  Thus this is not a complete example, but simply a
1085       demonstration of the available functionality.
1086
1087       Here is a sample Xstartup script:
1088
1089            #!/bin/sh
1090            #
1091            # Xstartup
1092            #
1093            # This program is run as root after the user is verified
1094            #
1095            if [ -f /etc/nologin ]; then
1096                 xmessage -file /etc/nologin -timeout 30 -center
1097                 exit 1
1098            fi
1099            sessreg -a -l $DISPLAY -x /etc/X11/xdm/Xservers $LOGNAME
1100            /etc/X11/xdm/GiveConsole
1101            exit 0
1102

SESSION PROGRAM

1104       The Xsession program is the command which is run as the user's session.
1105       It is run with the permissions of the authorized user.
1106
1107       In addition to any specified by DisplayManager.exportList, the  follow‐
1108       ing environment variables are passed:
1109
1110            DISPLAY        the associated display name
1111            HOME           the initial working directory of the user
1112            LOGNAME        the user name
1113            USER           the user name
1114            PATH           the value of DisplayManager.DISPLAY.userPath
1115            SHELL          the user's default shell (from getpwnam)
1116            XAUTHORITY     may be set to a non-standard authority file
1117            KRB5CCNAME     may be set to a Kerberos credentials cache name
1118            WINDOWPATH     may be set to the "window path" leading to the X server
1119
1120
1121       At  most installations, Xsession should look in $HOME for a file .xses‐
1122       sion, which contains commands that each user would like  to  use  as  a
1123       session.  Xsession should also implement a system default session if no
1124       user-specified session exists.
1125
1126       An argument may be passed to this program from the authentication  wid‐
1127       get  using  the  `set-session-argument'  action.   This  can be used to
1128       select different styles of session.  One good use of this feature is to
1129       allow the user to escape from the ordinary session when it fails.  This
1130       allows users to repair their own .xsession if it fails, without requir‐
1131       ing  administrative  intervention.   The example following demonstrates
1132       this feature.
1133
1134       This example recognizes the special ``failsafe'' mode, specified in the
1135       translations  in  the  Xresources  file,  to provide an escape from the
1136       ordinary session.  It also requires that the  .xsession  file  be  exe‐
1137       cutable so we don't have to guess what shell it wants to use.
1138
1139            #!/bin/sh
1140            #
1141            # Xsession
1142            #
1143            # This is the program that is run as the client
1144            # for the display manager.
1145
1146            case $# in
1147            1)
1148                 case $1 in
1149                 failsafe)
1150                      exec xterm -geometry 80x24-0-0
1151                      ;;
1152                 esac
1153            esac
1154
1155            startup=$HOME/.xsession
1156            resources=$HOME/.Xresources
1157
1158            if [ -f "$startup" ]; then
1159                 exec "$startup"
1160            else
1161                 if [ -f "$resources" ]; then
1162                      xrdb -load "$resources"
1163                 fi
1164                 twm &
1165                 xman -geometry +10-10 &
1166                 exec xterm -geometry 80x24+10+10 -ls
1167            fi
1168
1169
1170       The  user's  .xsession  file  might  look  something like this example.
1171       Don't forget that the file must have execute permission.
1172            #! /bin/csh
1173            # no -f in the previous line so .cshrc gets run to set $PATH
1174            twm &
1175            xrdb -merge "$HOME/.Xresources"
1176            emacs -geometry +0+50 &
1177            xbiff -geometry -430+5 &
1178            xterm -geometry -0+50 -ls
1179

RESET PROGRAM

1181       Symmetrical with Xstartup, the Xreset script is run after the user ses‐
1182       sion has terminated.  Run as root, it should contain commands that undo
1183       the effects of commands in Xstartup, updating entries in utmp  or  wtmp
1184       files,  or  unmounting  directories from file servers.  The environment
1185       variables that were passed to Xstartup are also passed to Xreset.
1186
1187       A sample Xreset script:
1188            #!/bin/sh
1189            #
1190            # Xreset
1191            #
1192            # This program is run as root after the session ends
1193            #
1194            sessreg -d -l $DISPLAY -x /etc/X11/xdm/Xservers $LOGNAME
1195            /etc/X11/xdm/TakeConsole
1196            exit 0
1197

CONTROLLING THE SERVER

1199       Xdm controls local servers using POSIX signals.  SIGHUP is expected  to
1200       reset  the  server, closing all client connections and performing other
1201       cleanup duties.  SIGTERM is expected to terminate the server.  If these
1202       signals  do not perform the expected actions, the resources DisplayMan‐
1203       ager.DISPLAY.resetSignal  and   DisplayManager.DISPLAY.termSignal   can
1204       specify alternate signals.
1205
1206       To  control  remote  terminals not using XDMCP, xdm searches the window
1207       hierarchy on the display and uses the protocol request KillClient in an
1208       attempt  to  clean  up the terminal for the next session.  This may not
1209       actually kill all of the clients, as only those which have created win‐
1210       dows  will  be noticed.  XDMCP provides a more sure mechanism; when xdm
1211       closes its initial connection, the session is over and the terminal  is
1212       required to close all other connections.
1213

CONTROLLING XDM

1215       Xdm  responds  to two signals: SIGHUP and SIGTERM.  When sent a SIGHUP,
1216       xdm rereads the configuration file, the access control  file,  and  the
1217       servers  file.   For  the servers file, it notices if entries have been
1218       added or removed.  If a new entry has been added, xdm starts a  session
1219       on  the  associated  display.  Entries which have been removed are dis‐
1220       abled immediately, meaning that any session in progress will be  termi‐
1221       nated without notice and no new session will be started.
1222
1223       When sent a SIGTERM, xdm terminates all sessions in progress and exits.
1224       This can be used when shutting down the system.
1225
1226       Xdm attempts to mark its various sub-processes for ps(1) by editing the
1227       command  line argument list in place.  Because xdm can't allocate addi‐
1228       tional space for this task, it is useful to start xdm with a reasonably
1229       long  command  line  (using the full path name should be enough).  Each
1230       process which is servicing a display is marked -display.
1231

ADDITIONAL LOCAL DISPLAYS

1233       To add an additional local display, add a line for it to  the  Xservers
1234       file.  (See the section Local Server Specification.)
1235
1236       Examine the display-specific resources in xdm-config (e.g., DisplayMan‐
1237       ager._0.authorize) and consider which of them should be copied for  the
1238       new  display.  The default xdm-config has all the appropriate lines for
1239       displays :0 and :1.
1240

OTHER POSSIBILITIES

1242       You can use xdm to run a single session at a time, using the  4.3  init
1243       options  or  other suitable daemon by specifying the server on the com‐
1244       mand line:
1245
1246            xdm -server “:0 SUN-3/60CG4 local /usr/bin/X :0”
1247
1248
1249       Or, you might have a file server and a collection of X terminals.   The
1250       configuration  for  this  is  identical to the sample above, except the
1251       Xservers file would look like
1252
1253            extol:0 VISUAL-19 foreign
1254            exalt:0 NCD-19 foreign
1255            explode:0 NCR-TOWERVIEW3000 foreign
1256
1257
1258       This directs xdm to manage sessions on all three  of  these  terminals.
1259       See  the  section Controlling Xdm for a description of using signals to
1260       enable and disable these terminals in a manner reminiscent of init(8).
1261

LIMITATIONS

1263       One thing that xdm isn't very good at doing is  coexisting  with  other
1264       window  systems.   To use multiple window systems on the same hardware,
1265       you'll probably be more interested in xinit.
1266

FILES

1268       /etc/X11/xdm/xdm-config
1269                           the default configuration file
1270
1271       $HOME/.Xauthority   user authorization file where xdm stores  keys  for
1272                           clients to read
1273
1274       /usr/libexec/chooser
1275                           the default chooser
1276
1277       /usr/bin/xrdb       the default resource database loader
1278
1279       /usr/bin/X          the default server
1280
1281       /usr/bin/xterm      the default session program and failsafe client
1282
1283       /var/lib/xdm/A<display>-<suffix>
1284                           the default place for authorization files
1285
1286       /tmp/K5C<display>   Kerberos credentials cache
1287

SEE ALSO

1289       X(7),    xinit(1),   xauth(1),   xrdb(1),   Xsecurity(7),   sessreg(1),
1290       Xserver(1), xdmshell(1), fonts.conf(5).
1291       X Display Manager Control Protocol
1292       IETF RFC 4291: IP Version 6 Addressing Architecture.
1293

AUTHOR

1295       Keith Packard, MIT X Consortium
1296
1297
1298
1299X Version 11                      xdm 1.1.11                            XDM(1)
Impressum