wdmx - Online in the Cloud

PROGRAM:

NAME

wdm - WINGs Display Manager

SYNOPSIS

wdm [ options ]

DESCRIPTION

wdm is an X display manager based on the original X11 X Display Manager (xdm). It
features numerous functionality improvements, including the ability to reboot or halt the
machine (once the proper password has been supplied) and to select from a list of
available X sessions to start. The look of the login panel is somewhat configurable, too.

OPTIONS

Except for -config, all of these options can be specified as resources.

-config configuration_file
Names the configuration file, which specifies resources to control the behavior of
wdm. #configdir#/wdm-config is the default.

-nodaemon
Specifies ``false'' as the value for the DisplayManager.daemonMode resource. This
suppresses the normal daemon behavior, which is for wdm 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 wdm to print lots of debugging statements to the terminal; it also
disables the DisplayManager.daemonMode resource, forcing wdm to run synchronously.
To interpret these debugging messages, a copy of the source code for wdm 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 wdm as well as anything written to stderr by the various
scripts and programs run during the progress of the session.

-syslog facility
Specifies the value for the DisplayManager.syslogFacility resource. This is
factility to use with all messages if log is redirected to syslog.

-usesyslog
Specifies ``true'' as the value for the DisplayManager.useSyslog resource. This
will force all messages go to syslog with facility specified by
DisplayManager.syslogFacility resource.

-useerrfile
Specifies ``false'' as the value for the DisplayManager.useSyslog resource. This
will force all messages go to log file specified by DisplayManager.errorLogFile
resource.

-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.

-udpPort port_number
Specifies the value for the DisplayManager.requestPort resource. This sets the
port-number which wdm will monitor for XDMCP requests. As XDMCP uses the
registered well-known UDP port 177, this resource should not be changed except for
debugging. If set to 0 wdm will not listen for XDMCP or Chooser requests.

-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.

RESOURCES

At many stages the actions of wdm can be controlled through the use of its configuration
file, which is in the X resource format. Some resources modify the behavior of wdm 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; wdm 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
request.

Because the resource manager uses colons to separate the name of the resource from its
value and dots to separate resource name parts, wdm 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.

DisplayManager.servers
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.

DisplayManager.requestPort
This indicates the UDP port number which wdm uses to listen for incoming XDMCP
requests. Unless you need to debug the system, leave this with its default value
of 177.

DisplayManager.errorLogFile
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.

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

DisplayManager.daemonMode
Normally, wdm 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.

DisplayManager.pidFile
The filename specified will be created to contain an ASCII representation of the
process-id of the main wdm 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.

DisplayManager.lockPidFile
This is the resource which controls whether wdm 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.

DisplayManager.authDir
This names a directory under which wdm stores authorization files while
initializing the session. The default value is #configdir#. Can be overridden for
specific displays by DisplayManager.DISPLAY.authFile.

DisplayManager.autoRescan
This boolean controls whether wdm 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 wdm to reread these files by
sending a SIGHUP to the main process.

DisplayManager.removeDomainname
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, wdm 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.''

DisplayManager.keyFile
XDM-AUTHENTICATION-1 style XDMCP authentication requires that a private key be
shared between wdm and the terminal. This resource specifies the file containing
those values. Each entry in the file consists of a display name and the shared
key. By default, wdm does not include support for XDM-AUTHENTICATION-1, as it
requires DES which is not generally distributable because of United States export
restrictions.

DisplayManager.accessFile
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.

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

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

DisplayManager.greeterLib
On systems that support a dynamically-loadable greeter library, the name of the
library. The default is /usr/lib/X11/xdm/libXdmGreet.so. This not used in Debian.

DisplayManager.choiceTimeout
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.

DisplayManager.sourceAddress
Use the numeric IP address of the incoming connection on multihomed hosts instead
of the host name. This is to avoid trying to connect on the wrong interface which
might be down at this time.

DisplayManager.willing
This specifies a program which is run (as) root when an an XDMCP BroadcastQuery is
received and this host is configured to offer XDMCP display management. The output
of this program may be displayed on a chooser window. If no program is specified,
the string Willing to manage is sent.

DisplayManager.DISPLAY.resources
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 #configdir#/Xresources is the
conventional name.

DisplayManager.DISPLAY.chooser
Specifies the program run to offer a host menu for Indirect queries redirected to
the special host name CHOOSER. /usr/X11R6/bin/chooser is the default. See the
sections XDMCP Access Control and Chooser.

DisplayManager.DISPLAY.xrdb
Specifies the program used to load the resources. By default, wdm uses
/usr/X11R6/bin/xrdb.

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

DisplayManager.DISPLAY.setup
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.

DisplayManager.DISPLAY.startup
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.

DisplayManager.DISPLAY.session
This specifies the session to be executed (not running as root). By default,
/usr/X11R6/bin/xterm is run. The conventional name is Xsession. See the section
Session Program.

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

DisplayManager.DISPLAY.openDelay

DisplayManager.DISPLAY.openRepeat

DisplayManager.DISPLAY.openTimeout

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

DisplayManager.DISPLAY.pingInterval

DisplayManager.DISPLAY.pingTimeout
To discover when remote displays disappear, wdm 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.
wdm 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.

DisplayManager.DISPLAY.terminateServer
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.''

DisplayManager.DISPLAY.userPath
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
DefaultUserPath.

DisplayManager.DISPLAY.systemPath
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 schemes.

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

DisplayManager.DISPLAY.failsafeClient
If the default session fails to execute, wdm 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, /usr/X11R6/bin/xterm is used.

DisplayManager.DISPLAY.grabServer

DisplayManager.DISPLAY.grabTimeout
To improve security, wdm 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 wdm 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, wdm kills and restarts the server (if possible) and the session.

DisplayManager.DISPLAY.authorize

DisplayManager.DISPLAY.authName
authorize is a boolean resource which controls whether wdm generates and uses
authorization for the local server connections. If authorization is used, authName
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-
AUTHORIZATION-1 MIT-MAGIC-COOKIE-1.''

DisplayManager.DISPLAY.authFile
This file is used to communicate the authorization data from wdm 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 not specified, a name is generated from
DisplayManager.authDir and the name of the display.

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

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

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

DisplayManager.DISPLAY.resetForAuth
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 wdm generates the authorization information just before connecting
to the display, an old server would not get up-to-date authorization information.
This resource causes wdm 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 servers.

DisplayManager.DISPLAY.userAuthDir
When wdm 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. It uses /tmp by default.

DisplayManager.wdmLogin
Specifies the path to wdmLogin(1x)

DisplayManager.wdmWm
Is a colon separated list of window managers to use as options in the login panel.
Note that if you include the path to the window manager, it will look ugly. You may
set this resource to None if you want only NoChange to appear.

DisplayManager.wdmLogo
Path to the logo pixmap, several formats are accepted, read wdmLogin(1x) to find
out more.

DisplayManager.wdmHelpFile
Path to a text file which will be displayed in the help panel, read wdmLogin(1x) to
find out more.

DisplayManager.wdmDefaultUser
a default username which will be used if no username is typed.

DisplayManager.wdmDefaultPasswd
the clear text password of the default user above. BE VERY CAREFUL when using this
two resources, and don't forget to do: chmod 600 wdm-config ; chown root.root wdm-
config

DisplayManager.wdmBg
Background specification. Read the BACKGROUND IMAGE SPECIFICATION section to find
out about the format. If this is not specified, then the background is not set.

DisplayManager.wdmReboot
Reboot command.

DisplayManager.wdmHalt
Halt command.

DisplayManager.wdmVerify
If true, verify user's identity for reboot/halt/exit.

DisplayManager.wdmRoot
If true, user must be root to exit.

DisplayManager.wdmAnimations
If true, enable animations consisting of shaking the panel (if an error) and
rolling up the panel (when closing it). If false, animations are disabled.

DisplayManager.wdmLocale
LANG environment variable will be set to value of this resource before starting
wdmLogin.

DisplayManger.wdmCursorTheme
If you have recent version of XFree with support for transparent cursors you can
select cursor theme to use on login panel. XCURSOR_THEME environment variable will
be set to value of this resource before starting wdmLogin.

CONFIGURATION FILE

The default location of the wdm configuration file is #configdir#/wdm-config

Here is a reasonable configuration file, which could be named wdm-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 discussion.
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 excluded.

To only respond to Direct queries for a host or pattern, it can be followed by the
optional ``NOBROADCAST'' keyword. This can be used to prevent an wdm server from
appearing on menus based on Broadcast queries.

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 wdm run chooser to offer a menu of hosts to
connect to. See the section Chooser.

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

*.deshaw.com NOBROADCAST # allow only direct access
*.gw.com # allow direct and broadcast

#
# 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

RESOURCES FILE

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
#endif

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 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.

SETUP PROGRAM

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 wdm 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 DisplayManager.DISPLAY.resources.

Here is a sample Xsetup script:

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

BACKGROUND IMAGE SPECIFICATION

There are several possible ways of specifying a background image. The generic format is
type:image. type can be any of:

none The backgound is not set.

solid it renders a solid background, and image is a color name

hgradient, vgradient, dgradient
a gradient (either horizontal, vertical or diagonal) will be rendered. image is
comma separated of color names, and any number of colors can be specified.

pixmap a pixmap will be used for the background. image is the full path to an image file
(tiff, png, jpeg and xpm allowed) and it will be scaled to use the full screen.

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