This chapter documents the files that control &tdm;'s behaviour. Some of this can be also controlled from the &kcontrol; module, but not all. The basic format of the file is INI-like. Options are key/value pairs, placed in sections. Everything in the file is case sensitive. Syntactic errors and unrecognised key/section identifiers cause &tdm; to issue non-fatal error messages. Lines beginning with # are comments; empty lines are ignored as well. Sections are denoted by [Name of Section]. You can configure every X-display individually. Every display has a display name, which consists of a host name (which is empty for local displays specified in the Xservers file), a colon and a display number. Additionally, a display belongs to a display class (which can be ignored in most cases). Sections with display-specific settings have the formal syntax [X- host [ : number [ _ class ] ] - sub-section ] All sections with the same sub-section make up a section class. You can use the * wildcard for host, number and class. You may omit trailing components; they are assumed to be * then. The host part may be a domain specification like .inf.tu-dresden.de. From which section a setting is actually taken is determined by these rules: An exact match takes precedence over a partial match (for the host part), which in turn takes precedence over a wildcard. Precedence decreases from left to right for equally exact matches. Example: display name myhost:0, class dpy [X-myhost:0_dpy] precedes [X-myhost:0_*] (same as [X-myhost:0]) precedes [X-myhost:*_dpy] precedes [X-myhost:*_*] (same as [X-myhost]) precedes [X-*:0_dpy] precedes [X-*:0_*] (same as [X-*:0]) precedes [X-*:*_*] (same as [X-*]). These sections do not match this display: [X-hishost], [X-myhost:0_dec], [X-*:1], [X-:*] Common sections are [X-*] (all displays), [X-:*] (all local displays) and [X-:0] (the first local display). The format for all keys is key = value. Keys are only valid in the section class they are defined for. Some keys do not apply to particular displays, in which case they are ignored. If a setting is not found in any matching section, the default is used. A pristine &tdmrc; is very thoroughly commented. All comments will be lost if you change this file with the kcontrol frontend. This section contains global options that do not fit into any specific section. ConfigVersion This option exists solely for the purpose of clean automatic upgrades. Do not change it, you may interfere with future upgrades and this could result in &tdm; failing to run. Xservers If the value starts with a slash (/), it specifies a file to read &X-Server; definitions from; otherwise, it is an &X-Server; definition by itself. See for the details. The default is an &X-Server; definition that is usually reasonable for the system on which &tdm; was built. ServerVTs List of Virtual Terminals to allocate to &X-Server;s. For negative numbers the absolute value is used, and the VT will be allocated only if the kernel says it is free. If &tdm; exhausts this list, it will allocate free VTs greater than the absolute value of the last entry in this list. Empty by default. PidFile The filename specified will be created to contain an ASCII representation of the process ID of the main &tdm; process; the PID will not be stored if the filename is empty. Empty by default. LockPidFile This option controls whether &tdm; uses file locking to keep multiple display managers from running onto each other. The default is true. AuthDir This names a directory under which &tdm; stores &X-Server; authorisation files while initialising the session. &tdm; expects the system to clean up this directory from stale files on reboot. The authorisation file to be used for a particular display can be specified with the AuthFile option in [X-*-Core]. The default is /var/run/xauth. AutoRescan This boolean controls whether &tdm; automatically re-reads its configuration files if it finds them to have changed. The default is true. ExportList Additional environment variables &tdm; should pass on to all programs it runs. LD_LIBRARY_PATH and XCURSOR_THEME are good candidates; otherwise, it should not be necessary very often. Empty by default. RandomFile If the system has no native entropy source like /dev/urandom (see RandomDevice) and no entropy daemon like EGD (see PrngdSocket and PrngdPort) is running, &tdm; will fall back to its own pseudo-random number generator that will, among other things, successively checksum parts of this file (which, obviously, should change frequently). This option does not exist on Linux and various BSDs. The default is /dev/mem. PrngdSocket If the system has no native entropy source like /dev/urandom (see RandomDevice), read random data from a Pseudo-Random Number Generator Daemon, like EGD (http://egd.sourceforge.net) via this UNIX domain socket. This option does not exist on Linux and various BSDs. Empty by default. PrngdPort Same as PrngdSocket, only use a TCP socket on localhost. RandomDevice The path to a character device which TDM should read random data from. Empty means to use the system's preferred entropy device if there is one. This option does not exist on OpenBSD, as it uses the arc4_random function instead. Empty by default. FifoDir The directory in which the command FiFos should be created; make it empty to disable them. The default is /var/run/xdmctl. FifoGroup The group to which the global command FiFo should belong; can be either a name or a numerical ID. DataDir The directory in which &tdm; should store persistent working data; such data is, for example, the previous user that logged in on a particular display. The default is /var/lib/tdm. DmrcDir The directory in which &tdm; should store users' .dmrc files. This is only needed if the home directories are not readable before actually logging in (like with AFS). Empty by default. This section contains options that control &tdm;'s handling of &XDMCP; requests. Enable Whether &tdm; should listen to incoming &XDMCP; requests. The default is true. Port This indicates the UDP port number which &tdm; uses to listen for incoming &XDMCP; requests. Unless you need to debug the system, leave this with its default value. The default is 177. KeyFile XDM-AUTHENTICATION-1 style &XDMCP; authentication requires a private key to be shared between &tdm; and the terminal. This option specifies the file containing those values. Each entry in the file consists of a display name and the shared key. Empty by default. Xaccess To prevent unauthorised &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 default is ${kde_confdir}/tdm/Xaccess. ChoiceTimeout Number of seconds to wait for the display to respond after the 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. The default is 15. 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, &tdm; 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 option is enabled. The default is true. 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. The default is false. Willing This specifies a program which is run (as root) when an &XDMCP; DirectQuery or BroadcastQuery is received and this host is configured to offer &XDMCP; display management. The output of this program may be displayed in a chooser window. If no program is specified, the string Willing to manage is sent. Empty by default. This section contains global options concerning system shutdown. HaltCmd The command to run to halt/poweroff the system. The default is something reasonable for the system on which &tdm; was built, like /sbin/shutdown -h now. RebootCmd The command to run to reboot the system. The default is something reasonable for the system &tdm; on which was built, like /sbin/shutdown -r now. AllowFifo Whether it is allowed to shut down the system via the global command FiFo. The default is false. AllowFifoNow Whether it is allowed to abort active sessions when shutting down the system via the global command FiFo. This will have no effect unless AllowFifo is enabled. The default is true. UseLilo Instructs &tdm; to offer LiLo boot options in the shutdown dialogue. Only available on Linux i386 & x86-64. The default is false. LiloCmd The location of the LiLo binary. Only available on Linux i386 & x86-64. The default is /sbin/lilo. LiloMap The location of the map file LiLo should use. Only available on Linux i386 & x86-64. The default is /boot/map. This section class contains options concerning the configuration of the &tdm; backend (core). OpenDelay See OpenRepeat. The default is 15. OpenTimeout See OpenRepeat. The default is 120. OpenRepeat These options control the behaviour of &tdm; when attempting to open a connection to an &X-Server;. OpenDelay is the length of the pause (in seconds) between successive attempts, OpenRepeat is the number of attempts to make and OpenTimeout is the amount of time to spend on a connection attempt. After OpenRepeat attempts have been made, or if OpenTimeout seconds elapse in any particular connection attempt, the start attempt is considered failed. The default is 5. StartAttempts How many times &tdm; should attempt to start a foreign display listed in the Xservers file before giving up and disabling it. Local displays are attempted only once, and &XDMCP; displays are retried indefinitely by the client (unless the option -once was given to the &X-Server;). The default is 4. ServerAttempts How many times &tdm; should attempt to start up a local &X-Server;. Starting up includes executing it and waiting for it to come up. The default is 1. ServerTimeout How many seconds &tdm; should wait for a local &X-Server; to come up. The default is 15. PingInterval See PingTimeout. The default is 5. PingTimeout To discover when remote displays disappear, &tdm; regularly pings them. PingInterval specifies the time (in minutes) between the pings and 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. If you frequently use X terminals which can become isolated from the managing host, you may wish to increase the timeout. The only worry is that sessions will continue to exist after the terminal has been accidentally disabled. The default is 5. TerminateServer Whether &tdm; should restart the local &X-Server; after session exit instead of resetting it. Use this if the &X-Server; leaks memory or crashes the system on reset attempts. The default is false. ResetSignal The signal number to use to reset the local &X-Server;. The default is 1 (SIGHUP). TermSignal The signal number to use to terminate the local &X-Server;. The default is 15 (SIGTERM). Authorise Controls whether &tdm; generates and uses authorisation for local &X-Server; connections. For &XDMCP; displays the authorisation requested by the display is used; foreign non-&XDMCP; displays do not support authorisation at all. The default is true. AuthNames If Authorize is true, use the authorisation mechanisms listed herein. The MIT-MAGIC-COOKIE-1 authorisation is always available; XDM-AUTHORIZATION-1, SUN-DES-1 and MIT-KERBEROS-5 might be available as well, depending on the build configuration. The default is DEF_AUTH_NAME. ResetForAuth Some old &X-Server;s re-read the authorisation file at &X-Server; reset time, instead of when checking the initial connection. As &tdm; generates the authorisation information just before connecting to the display, an old &X-Server; would not get up-to-date authorisation information. This option causes &tdm; to send SIGHUP to the &X-Server; after setting up the file, causing an additional &X-Server; reset to occur, during which time the new authorisation information will be read. The default is false. AuthFile This file is used to communicate the authorisation data from &tdm; to the &X-Server;, using the -auth &X-Server; command line option. It should be kept in a directory which is not world-writable as it could easily be removed, disabling the authorisation mechanism in the &X-Server;. If not specified, a random name is generated from AuthDir and the name of the display. Empty by default. Resources This option 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. KDE programs generally do not use X-resources, so this option is only needed if the Setup program needs some X-resources. Empty by default. Xrdb The xrdb program to use to read the X-resources file specified in Recources. The default is ${x_bindir}/xrdb. Setup This specifies a program which is run (as root) before offering the greeter window. This may be used to change the appearance of the screen around the greeter window or to put up other windows (e.g., you may want to run xconsole here). The conventional name for a file used here is Xsetup. See . Empty by default. Startup This specifies a program which is run (as root) after the user authentication process succeeds. The conventional name for a file used here is Xstartup. See . Empty by default. Reset This specifies a program which is run (as root) after the session terminates. The conventional name for a file used here is Xreset. See . Empty by default. Session This specifies the session program to be executed (as the user owning the session). The conventional name for a file used here is Xsession. See . The default is ${x_bindir}/xterm -ls -T. FailsafeClient If the Session program fails to execute, &tdm; 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 default is ${x_bindir}/xterm. UserPath The PATH environment variable for non-root Sessions. The default depends on the system &tdm; was built on. SystemPath The PATH environment variable for all programs but non-root Sessions. Note that it is good practice not to include . (the current directory) into this entry. The default depends on the system &tdm; was built on. SystemShell The SHELL environment variable for all programs but the Session. The default is /bin/sh. UserAuthDir When &tdm; is unable to write to the usual user authorisation file ($HOME/.Xauthority), it creates a unique file name in this directory and points the environment variable XAUTHORITY at the created file. The default is /tmp. AutoReLogin If enabled, &tdm; will automatically restart a session after an &X-Server; crash (or if it is killed by Alt-Ctrl-BackSpace). Note that enabling this feature opens a security hole: a secured display lock can be circumvented (unless &kde;'s built-in screen locker is used). The default is false. AllowRootLogin If disabled, do not allow root (and any other user with UID = 0) to log in directly. The default is true. AllowNullPasswd If disabled, only users that have passwords assigned can log in. The default is true. AllowShutdown Who is allowed to shut down the system. This applies both to the greeter and to the command FiFo. None no Shutdown... menu entry is shown at all Root the root password must be entered to shut down All everybody can shut down the machine The default is All. AllowSdForceNow Who is allowed to abort active sessions when shutting down. None no forced shutdown is allowed at all Root the root password must be entered to shut down forcibly All everybody can shut down the machine forcibly The default is All. DefaultSdMode The default choice for the shutdown condition/timing. Schedule shut down after all active sessions exit (possibly at once) TryNow shut down, if no active sessions are open; otherwise, do nothing ForceNow shut down unconditionally The default is Schedule. ScheduledSd How to offer shutdown scheduling options: Never not at all Optional as a button in the simple shutdown dialogues Always instead of the simple shutdown dialogues The default is Never. NoPassEnable Enable password-less logins on this display. Use with extreme care! The default is false. NoPassUsers The users that do not need to provide a password to log in. Items which are prefixed with @ represent all users in the user group named by that item. * means all users but root (and any other user with UID = 0). Never list root. Empty by default. AutoLoginEnable Enable automatic login. Use with extreme care! The default is false. AutoLoginUser The user to log in automatically. Never specify root! Empty by default. AutoLoginPass The password for the user to log in automatically. This is not required unless the user is logged into a NIS or Kerberos domain. If you use this option, you should chmod 600 tdmrc for obvious reasons. Empty by default. SessionsDirs A list of directories containing session type definitions. The default is ${kde_datadir}/tdm/sessions. ClientLogFile The file (relative to the user's home directory) to redirect the session output to. One occurrence of %s in this string will be substituted with the display name. Use %% to obtain a literal %. The default is .xsession-errors. This section class contains options concerning the configuration of the &tdm; frontend (greeter). GUIStyle Specify the widget style for the greeter. Empty means to use the built-in default which currently is Keramik. Empty by default. ColorScheme Specify the widget colour scheme for the greeter. Empty means to use the built-in default which currently is yellowish grey with some light blue and yellow elements. Empty by default. LogoArea What should be shown in the greeter righthand of the input lines (if UserList is disabled) or above them (if UserList is enabled): None nothing Logo the image specified by LogoPixmap Clock a neat analogue clock The default is Clock. LogoPixmap The image to show in the greeter if LogoArea is Logo. Empty by default. GreeterPos The relative coordinates (percentages of the screen size; X,Y) at which the centre of the greeter is put. &tdm; aligns the greeter to the edges of the screen it would cross otherwise. The default is 50,50. GreeterScreen The screen the greeter should be displayed on in multi-headed and Xinerama setups. The numbering starts with 0. For Xinerama, it corresponds to the listing order in the active ServerLayout section of XF86Config; -1 means to use the upper-left screen, -2 means to use the upper-right screen. GreetString The headline in the greeter. An empty greeting means none at all. The following character pairs are replaced by their value: %d name of the current display %h local host name, possibly with the domain name %n local node name, most probably the host name without the domain name %s operating system %r operating system version %m machine (hardware) type %% a single % The default is Welcome to %s at %n. GreetFont The font for the greeter headline. The default is charter,24,bold. StdFont The normal font used in the greeter. The default is helvetica,12. FailFont The font used for the Login Failed message. The default is helvetica,12,bold. AntiAliasing Whether the fonts used in the greeter should be antialiased. The default is false. NumLock What to do with the Num Lock modifier for the time the greeter is running: Off turn off On turn on Keep do not change the state The default is Keep. Language Language and locale to use in the greeter, encoded like $LC_LANG. The default is en_US. UserCompletion Enable autocompletion in the username line edit. The default is false. UserList Show a user list with unix login names, real names and images in the greeter. The default is true. ShowUsers This option controls which users will be shown in the user view (UserList) and/or offered for autocompletion (UserCompletion). If it is Selected, SelectedUsers contains the final list of users. If it is NotHidden, the initial user list are all users found on the system. Users contained in HiddenUsers are removed from the list, just like all users with a UID greater than specified in MaxShowUID and users with a non-zero UID less than specified in MinShowUID. Items in SelectedUsers and HiddenUsers which are prefixed with @ represent all users in the user group named by that item. Finally, the user list will be sorted alphabetically, if SortUsers is enabled. The default is NotHidden. SelectedUsers See ShowUsers. Empty by default. HiddenUsers See ShowUsers. Empty by default. MinShowUID See ShowUsers. MaxShowUID See ShowUsers. The default is 65535. SortUsers See ShowUsers. The default is true. FaceSource If UserList is enabled, this specifies where &tdm; gets the images from: AdminOnly from <FaceDir>/$USER.face[.icon] PreferAdmin prefer <FaceDir>, fallback on $HOME PreferUser ... and the other way round UserOnly from the user's $HOME/.face[.icon] The images can be in any format Qt recognises, but the filename must match &tdm;'s expectations: .face.icon should be a 48x48 icon, while .face should be a 300x300 image. Currently the big image is used only as a fallback and is scaled down, but in the future it might be displayed full-size in the logo area or a tooltip. The default is AdminOnly. FaceDir See FaceSource. The default is ${kde_datadir}/tdm/faces. PreselectUser Specify, if/which user should be preselected for log in: None do not preselect any user Previous the user which successfully logged in last time Default the user specified in the DefaultUser option If FocusPasswd is enabled and a user was preselected, the cursor is placed in the password input field automatically. Enabling user preselection can be considered a security hole, as it presents a valid login name to a potential attacker, so he only needs to guess the password. On the other hand, one could set DefaultUser to a fake login name. The default is None. DefaultUser See PreselectUser. Empty by default. FocusPasswd See PreselectUser. The default is false. EchoMode The password input fields cloak the typed in text. Specify, how to do it: OneStar * is shown for every typed letter ThreeStars *** is shown for every typed letter NoEcho nothing is shown at all, the cursor does not move The default is OneStar. UseBackground If enabled, &tdm; will automatically start the krootimage program to set up the background; otherwise, the Setup program is responsible for the background. The default is true. BackgroundCfg The configuration file to be used by krootimage. It contains a section named [Desktop0] like kdesktoprc does. Its options are not described herein; guess their meanings or use the control centre. The default is ${kde_confdir}/tdm/backgroundrc. GrabServer To improve security, the greeter grabs the &X-Server; and then the keyboard when it starts up. This option specifies if the &X-Server; grab should be held for the duration of the name/password reading. When disabled, the &X-Server; is ungrabbed after the keyboard grab succeeds; otherwise, the &X-Server; is grabbed until just before the session begins. Enabling this option disables UseBackground and Setup. The default is false. GrabTimeout This option specifies the maximum time &tdm; will wait for the grabs to succeed. A grab may fail if some other X-client has the &X-Server; or the keyboard grabbed, or possibly if the network latencies are very high. You should be cautious when raising the timeout, as a user can be spoofed by a look-alike window on the display. If a grab fails, &tdm; kills and restarts the &X-Server; (if possible) and the session. The default is 3. AuthComplain Warn, if a display has no X-authorisation. This will be the case if the authorisation file for a local &X-Server; could not be created, a remote display from &XDMCP; did not request any authorisation or the display is a foreign display from the Xservers file. The default is true. LoginMode Specify whether the greeter of local displays should start up in host chooser (remote) or login (local) mode and whether it is allowed to switch to the other mode. LocalOnly only local login possible DefaultLocal start up in local mode, but allow switching to remote mode DefaultRemote ... and the other way round RemoteOnly only choice of remote host possible The default is LocalOnly. ChooserHosts A list of hosts to be automatically added to the remote login menu. The special name * means broadcast. Has no effect if LoginMode is LocalOnly. The default is *. ForgingSeed Use this number as a random seed when forging saved session types, etc. of unknown users. This is used to avoid telling an attacker about existing users by reverse conclusion. This value should be random but constant across the login domain. ShowLog Enable &tdm;'s built-in xconsole. Note that this can be enabled for only one display at a time. This option is available only if &tdm; was configured with --enable-tdm-xconsole. The default is false. LogSource The data source for &tdm;'s built-in xconsole. If empty, a console log redirection is requested from /dev/console. Has no effect if ShowLog is disabled. Empty by default. PluginsLogin Specify conversation plugins for the login dialogue; the first in the list is selected initially. Each plugin can be specified as a base name (which expands to $kde_modulesdir/kgreet_base) or as a full pathname. Conversation plugins are modules for the greeter which obtain authentication data from the user. Currently only the classic plugin is shipped with &kde;; it presents the well-known username and password form. The default is classic. PluginsShutdown Same as PluginsLogin, but for the shutdown dialogue. The default is classic. PluginOptions A list of options of the form Key=Value. The conversation plugins can query these settings; it is up to them what possible keys are. Empty by default. AllowConsole Show the Console Login action in the greeter. For this to work, a console must be configured for this particular display, see . The default is true. AllowClose Show the Restart X Server/Close Connection action in the greeter. The default is true. Preloader A program to run while the greeter is visible. It is supposed to preload as much as possible of the session that is going to be started (most probably). Empty by default. Each specification indicates a display which should constantly be managed and which is not using &XDMCP;. This method is typically used only for local &X-Server;s that are started by &tdm;, but &tdm; can manage externally started (foreign) &X-Server;s as well, may they run on the local machine or rather remotely. The formal syntax of a specification is display name [display class] local[@tty] [reserve] server command for own &X-Server;s and display name [display class] foreign for foreign &X-Server;s. The display name must be something that can be passed in the -display option to an X program. This string is used to generate the display-specific section names, so be careful to match the names. The display name of &XDMCP; displays is derived from the display's address by reverse host name resolution. For configuration purposes, the localhost prefix from locally running &XDMCP; displays is not stripped to make them distinguishable from local &X-Server;s started by &tdm;. The display class portion is also used in the display-specific sections. This is useful if you have a large collection of similar displays (such as a corral of X terminals) and would like to set options for groups of them. When using &XDMCP;, the display is required to specify the display class, so the manual for your particular X terminal should document the display class string for your device. If it does not, you can run &tdm; in debug mode and grep the log for class. The tty specifies which text console an &X-Server; is covering, so &tdm; knows which console it should monitor for activity after switching to Console login to find out when the console session ends. Note that this concept (originating from Solaris) is not perfectly suited for Linux, as there &X-Server;s run on separate virtual terminals and consequently do not actually cover consoles (gettys). The reserve keyword instructs &tdm; to start the display not when &tdm; starts up, but when it is explicitly requested via the command FiFo. If reserve displays are specified, the &kde; menu will have a Start New Session item near the bottom; use that to activate a reserve display with a new login session. The monitor will switch to the new display, and you will have a minute to login. If there are no more reserve displays available, selecting the menu item will have no effect. The server command specifies the complete &X-Server; command line, including a display number for secondary displays. When &tdm; starts a session, it sets up authorisation data for the &X-Server;. For local servers, &tdm; passes -auth filename on the &X-Server;'s command line to point it at its authorisation data. For &XDMCP; displays, &tdm; passes the authorisation data to the &X-Server; via the Accept &XDMCP; message. The file specified by the AccessFile option provides information which &tdm; uses to control access from displays requesting service via &XDMCP;. The file contains four types of entries: entries which control the response to Direct and Broadcast queries, entries which control the response to Indirect queries, macro definitions for Indirect entries and entries which control on which network interfaces &tdm; listens for &XDMCP; queries. Blank lines are ignored, # is treated as a comment delimiter causing the rest of that line to be ignored and \ causes an immediately following newline to be ignored, allowing indirect host lists to span multiple lines. The format of the Direct entries is simple, either a host name or a pattern, which is compared against the host name of the display device. Patterns are distinguished from host names by the inclusion of one or more meta characters; * matches any sequence of 0 or more characters, and ? matches any single character. 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. Note that only the first network address returned for a host name is used. For patterns, only canonical host names are used in the comparison, so ensure that you do not attempt to match aliases. Host names from &XDMCP; queries always contain the local domain name even if the reverse lookup returns a short name, so you can use patterns for the local domain. Preceding the entry 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 a &tdm; 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 the queries should be forwarded. Indirect entries can be excluding as well, in which case a (valid) dummy host name must be supplied to make the entry distinguishable from a Direct entry. If compiled with IPv6 support, multicast address groups may also be included in the list of addresses the queries are forwarded to. If the indirect host list contains the keyword CHOOSER, Indirect queries are not forwarded, but instead a host chooser dialogue is displayed by &tdm;. The chooser will send a Direct query to each of the remaining host names in the list and offer a menu of all the hosts that respond. The host list may contain the keyword BROADCAST, to make the chooser send a Broadcast query as well; note that on some operating systems, UDP packets cannot be broadcast, so this feature will not work. 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. 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. The last entry type is the LISTEN directive. The formal syntax is  LISTEN [interface [multicast list]] If one or more LISTEN lines are specified, &tdm; listens for &XDMCP; requests only on the specified interfaces. interface may be a hostname or IP address representing a network interface on this machine, or the wildcard * to represent all available network interfaces. If multicast group addresses are listed on a LISTEN line, &tdm; joins the multicast groups on the given interface. For IPv6 multicasts, the IANA has assigned ff0X:0:0:0:0:0:0:12b as the permanently assigned range of multicast addresses for &XDMCP;. The X in the prefix may be replaced by any valid scope identifier, such as 1 for Node-Local, 2 for Link-Local, 5 for Site-Local, and so on (see IETF RFC 2373 or its replacement for further details and scope definitions). &tdm; defaults to listening on the Link-Local scope address ff02:0:0:0:0:0:0:12b to most closely match the IPv4 subnet broadcast behavior. If no LISTEN lines are given, &tdm; listens on all interfaces and joins the default &XDMCP; IPv6 multicast group (when compiled with IPv6 support). To disable listening for &XDMCP; requests altogether, a LISTEN line with no addresses may be specified, but using the [Xdmcp] Enable option is preferred. The following programs are run by &tdm; at various stages of a session. They typically are shell scripts. The Setup, Startup and Reset programs are run as root, so they should be careful about security. Their first argument is auto if the session results from an automatic login; otherwise, no arguments are passed to them. The Xsetup program is run after the &X-Server; is started or reset, but before the greeter is offered. This is the place to change the root background (if UseBackground is disabled) or bring up other windows that should appear on the screen along with the greeter. In addition to any specified by ExportList, the following environment variables are passed: DISPLAY the associated display name PATH the value of SystemPath SHELL the value of SystemShell XAUTHORITY may be set to an authority file DM_CONTROL the value of FifoDir Note that since &tdm; 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 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 Resources. The Xstartup program is run as root when the user logs in. This is the place to put commands which add entries to utmp (the sessreg program may be useful here), mount users' home directories from file servers, or abort the session if some requirements are not met (but note that on modern systems, many of these tasks are already taken care of by PAM modules). In addition to any specified by ExportList, the following environment variables are passed: DISPLAY the associated display name HOME the initial working directory of the user LOGNAME the username USER the username PATH the value of SystemPath SHELL the value of SystemShell XAUTHORITY may be set to an authority file DM_CONTROL the value of FifoDir &tdm; waits until this program exits before starting the user session. If the exit value of this program is non-zero, &tdm; discontinues the session and starts another authentication cycle. The Xsession program is the command which is run as the user's session. It is run with the permissions of the authorised user. One of the keywords failsafe, default or custom, or a string to eval by a Bourne-compatible shell is passed as the first argument. In addition to any specified by ExportList, the following environment variables are passed: DISPLAY the associated display name HOME the initial working directory of the user LOGNAME the username USER the username PATH the value of UserPath (or SystemPath for root user sessions) SHELL the user's default shell XAUTHORITY may be set to a non-standard authority file KRBTKFILE may be set to a Kerberos4 credentials cache name KRB5CCNAME may be set to a Kerberos5 credentials cache name DM_CONTROL the value of FifoDir XDM_MANAGED will contain a comma-separated list of parameters the session might find interesting, like the location of the command FiFo and its capabilities, and which conversation plugin was used for the login DESKTOP_SESSION the name of the session the user has chosen to run Symmetrical with Xstartup, the Xreset program is run after the user session has terminated. Run as root, it should contain commands that undo the effects of commands in Xstartup, removing entries from utmp or unmounting directories from file servers. The environment variables that were passed to Xstartup are also passed to Xreset.