NAME
xdm - X Display Manager with support for XDMCP, host chooser
SYNOPSIS
xdm
[
-config
configuration_file
] [
-nodaemon
] [
-debug
debug_level
] [
-error
error_log_file
] [
-resources
resource_file
] [
-server
server_entry
] [
-session
session_program
]
DESCRIPTION
Xdm
manages a collection of X displays, which may be on the local host
or remote servers. The design of
xdm
was guided by the needs of X terminals as well as The Open Group standard
XDMCP, the _X _D_i_s_p_l_a_y _M_a_n_a_g_e_r _C_o_n_t_r_o_l _P_r_o_t_o_c_o_l.
Xdm
provides services similar to those provided by _i_n_i_t, _g_e_t_t_y
and _l_o_g_i_n on character terminals: prompting for login name and password,
authenticating the user, and running a ``session.''
A ``session'' is defined by the lifetime of a particular process; in the
traditional character-based terminal world, it is the user's login shell.
In the
xdm
context, it is an arbitrary session manager. This is because in a windowing
environment, a user's login shell process does not necessarily have any
terminal-like interface with which to connect.
When a real session manager is not available, a window manager or terminal
emulator is typically used as the ``session manager,'' meaning that
termination of this process terminates the user's session.
When the session is terminated, _x_d_m
resets the X server and (optionally) restarts the whole process.
When _x_d_m receives an Indirect query via XDMCP, it can run a
_c_h_o_o_s_e_r process to
perform an XDMCP BroadcastQuery (or an XDMCP Query to specified hosts)
on behalf of the display and
offer a menu of possible hosts that offer XDMCP display management.
This feature is useful with X terminals that do not offer a host
menu themselves.
Xdm
can be configured to ignore BroadcastQuery messages from selected hosts.
This is useful when you don't want the host to appear in menus produced
by
chooser
or X terminals themselves.
Because
xdm
provides the first interface that users will see, it is designed to be
simple to use and easy to customize to the needs of a particular site.
Xdm
has many options, most of which have reasonable defaults. Browse through the
various sections of this manual,
picking and choosing the things you want to change.
Pay particular attention to the
Session Program
section, which will describe how to
set up the style of session desired.
OVERVIEW
_x_d_m is highly configurable, and most of its behavior can be
controlled by resource files and shell scripts. The names of these
files themselves are resources read from the file _x_d_m_-_c_o_n_f_i_g or
the file named by the --ccoonnffiigg option.
_x_d_m offers display management two different ways. It can manage
X servers running on the local machine and specified in
_X_s_e_r_v_e_r_s, and it can manage remote X servers (typically X
terminals) using XDMCP (the XDM Control Protocol)
as specified in the _X_a_c_c_e_s_s file.
The resources of the X clients run by _x_d_m outside the user's
session, including _x_d_m's own login window, can be
affected by setting resources in the _X_r_e_s_o_u_r_c_e_s file.
For X terminals that do not offer a menu of hosts to get display
management from, _x_d_m can collect willing hosts and run the
_c_h_o_o_s_e_r program to offer the user a menu.
For X displays attached to a host, this step is typically not used, as
the local host does the display management.
After resetting the X server, _x_d_m runs the _X_s_e_t_u_p script
to assist in setting up the screen the user sees along with the
_x_l_o_g_i_n widget.
The _x_l_o_g_i_n widget, which _x_d_m presents,
offers the familiar login and password prompts.
After the user logs in, _x_d_m runs the _X_s_t_a_r_t_u_p script as
root.
Then _x_d_m runs the _X_s_e_s_s_i_o_n script as the user. This
system session file may do some additional startup and typically runs
the _._x_s_e_s_s_i_o_n script in the user's home directory.
When the _X_s_e_s_s_i_o_n script exits, the session is over.
At the end of the session, the _X_r_e_s_e_t script is run to clean up,
the X server is reset, and the cycle starts over.
The file _/_v_a_r_/_l_o_g_/_x_d_m_._l_o_g will contain error
messages from
xdm
and anything output to stderr by _X_s_e_t_u_p_, _X_s_t_a_r_t_u_p_, _X_s_e_s_s_i_o_n
or _X_r_e_s_e_t.
When you have trouble getting
xdm
working, check this file to see if
xdm
has any clues to the trouble.
OPTIONS
All of these options, except --ccoonnffiigg itself,
specify values that can also be specified in the configuration file
as resources.
-
--ccoonnffiigg _c_o_n_f_i_g_u_r_a_t_i_o_n___f_i_l_e
Names the configuration file, which specifies resources to control
-
the behavior of
xdm.
/etc/X11/xdm/xdm-config
is the default.
See the section CCoonnffiigguurraattiioonn FFiillee.
-
--nnooddaaeemmoonn
Specifies ``false'' as the value for the DDiissppllaayyMMaannaaggeerr..ddaaeemmoonnMMooddee
-
resource.
This suppresses the normal daemon behavior, which is for
xdm
to close all file descriptors, disassociate itself from
the controlling terminal, and put
itself in the background when it first starts up.
-
--ddeebbuugg _d_e_b_u_g___l_e_v_e_l
Specifies the numeric value for the DDiissppllaayyMMaannaaggeerr..ddeebbuuggLLeevveell
-
resource. A non-zero value causes
xdm
to print lots of debugging statements to the terminal; it also disables the
DDiissppllaayyMMaannaaggeerr..ddaaeemmoonnMMooddee resource, forcing
xdm
to run synchronously. To interpret these debugging messages, a copy
of the source code for
xdm
is almost a necessity. No attempt has been
made to rationalize or standardize the output.
-
--eerrrroorr _e_r_r_o_r___l_o_g___f_i_l_e
Specifies the value for the DDiissppllaayyMMaannaaggeerr..eerrrroorrLLooggFFiillee resource.
-
This file contains errors from
xdm
as well as anything written to stderr by the various scripts and programs
run during the progress of the session.
-
--rreessoouurrcceess _r_e_s_o_u_r_c_e___f_i_l_e
Specifies the value for the DDiissppllaayyMMaannaaggeerr**rreessoouurrcceess resource. This file
-
is loaded using
xrdb
to specify configuration parameters for the
authentication widget.
-
--sseerrvveerr _s_e_r_v_e_r___e_n_t_r_y
Specifies the value for the DDiissppllaayyMMaannaaggeerr..sseerrvveerrss resource.
-
See the section
Local Server Specification
for a description of this resource.
-
--uuddppPPoorrtt _p_o_r_t___n_u_m_b_e_r
Specifies the value for the DDiissppllaayyMMaannaaggeerr..rreeqquueessttPPoorrtt resource. This
-
sets the port-number which
xdm
will monitor for XDMCP requests. As XDMCP
uses the registered well-known UDP port 177, this resource should
not be changed except for debugging. If set to 0 xdm will not listen
for XDMCP or Chooser requests.
-
--sseessssiioonn _s_e_s_s_i_o_n___p_r_o_g_r_a_m
Specifies the value for the DDiissppllaayyMMaannaaggeerr**sseessssiioonn resource. This
-
indicates the program to run as the session after the user has logged in.
-
--xxrrmm _r_e_s_o_u_r_c_e___s_p_e_c_i_f_i_c_a_t_i_o_n
Allows an arbitrary resource to be specified, as in most
-
X Toolkit applications.
RESOURCES
At many stages the actions of
xdm
can be controlled through the use of its configuration file, which is in the
X resource format.
Some resources modify the behavior of
xdm
on all displays,
while others modify its behavior on a single display. Where actions relate
to a specific display,
the display name is inserted into the resource name between
``DisplayManager'' and the final resource name segment.
For local displays, the resource name and class are as read from the
_X_s_e_r_v_e_r_s file.
For remote displays, the resource name is what the network address of
the display resolves to. See the rreemmoovveeDDoommaaiinn resource. The
name must match exactly; _x_d_m 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,
xdm
substitutes underscores for both dots and colons when generating the resource
name.
For example, DDiissppllaayyMMaannaaggeerr..eexxppoo__xx__oorrgg__00..ssttaarrttuupp is the name of the
resource which defines the startup shell file for the ``expo.x.org:0'' display.
-
DDiissppllaayyMMaannaaggeerr..sseerrvveerrss
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 LLooccaall SSeerrvveerr SSppeecciiffiiccaattiioonn for the details.
-
DDiissppllaayyMMaannaaggeerr..rreeqquueessttPPoorrtt
This indicates the UDP port number which
-
xdm
uses to listen for incoming XDMCP requests. Unless you need to debug the
system, leave this with its default value of 177.
-
DDiissppllaayyMMaannaaggeerr..eerrrroorrLLooggFFiillee
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 _X_s_e_t_u_p_, _X_s_t_a_r_t_u_p_, _X_s_e_s_s_i_o_n and _X_r_e_s_e_t files,
so it will contain descriptions
of problems in those scripts as well.
-
DDiissppllaayyMMaannaaggeerr..ddeebbuuggLLeevveell
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
xdm,
which would normally not be useful.
-
DDiissppllaayyMMaannaaggeerr..ddaaeemmoonnMMooddee
Normally,
-
xdm
attempts to make itself into a daemon process unassociated with any terminal.
This is
accomplished by forking and leaving the parent process to exit, then closing
file descriptors and releasing the controlling terminal. In some
environments this is not desired (in particular, when debugging). Setting
this resource to ``false'' will disable this feature.
-
DDiissppllaayyMMaannaaggeerr..ppiiddFFiillee
The filename specified will be created to contain an ASCII
-
representation of the process-id of the main
xdm
process.
Xdm
also uses file locking on this file
to attempt to eliminate multiple daemons running on
the same machine, which would cause quite a bit of havoc.
-
DDiissppllaayyMMaannaaggeerr..lloocckkPPiiddFFiillee
This is the resource which controls whether
-
xdm
uses file locking to keep multiple display managers from running amok.
On System V, this
uses the _l_o_c_k_f library call, while on BSD it uses _f_l_o_c_k_.
-
DDiissppllaayyMMaannaaggeerr..aauutthhDDiirr
This names a directory under which
-
xdm
stores authorization files while initializing the session. The
default value is _/_v_a_r_/_d_b_/_x_d_m.
Can be overridden for specific displays by
DisplayManager._D_I_S_P_L_A_Y.authFile.
-
DDiissppllaayyMMaannaaggeerr..aauuttooRReessccaann
This boolean controls whether
-
xdm
rescans the configuration, servers, access control and authentication keys
files after a session terminates and the files have changed. By default it
is ``true.'' You can force
xdm
to reread these files by sending a SIGHUP to the main process.
-
DDiissppllaayyMMaannaaggeerr..rreemmoovveeDDoommaaiinnnnaammee
When computing the display name for XDMCP clients, the name resolver will
-
typically create a fully qualified host name for the terminal. As this is
sometimes confusing,
xdm
will remove the domain name portion of the host name if it is the same as the
domain name of the local host when this variable is set. By default the
value is ``true.''
-
DDiissppllaayyMMaannaaggeerr..kkeeyyFFiillee
XDM-AUTHENTICATION-1 style XDMCP authentication requires that a private key
-
be shared between
xdm
and the terminal. This resource specifies the file containing those
values. Each entry in the file consists of a display name and the shared
key. By default,
xdm
does not include support for XDM-AUTHENTICATION-1, as it requires DES which
is not generally distributable because of United States export restrictions.
-
DDiissppllaayyMMaannaaggeerr..aacccceessssFFiillee
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.
-
DDiissppllaayyMMaannaaggeerr..eexxppoorrttLLiisstt
A list of additional environment variables, separated by white space,
-
to pass on to the _X_s_e_t_u_p,
_X_s_t_a_r_t_u_p, _X_s_e_s_s_i_o_n, and _X_r_e_s_e_t programs.
-
DDiissppllaayyMMaannaaggeerr..rraannddoommFFiillee
A file to checksum to generate the seed of authorization keys.
-
This should be a file that changes frequently.
The default is _/_d_e_v_/_m_e_m.
-
DDiissppllaayyMMaannaaggeerr..ggrreeeetteerrLLiibb
On systems that support a dynamically-loadable greeter library, the
-
name of the library. The default is
_/_u_s_r_/_X_1_1_R_6_/_l_i_b_e_x_e_c_/_l_i_b_X_d_m_G_r_e_e_t_._s_o.
-
DDiissppllaayyMMaannaaggeerr..cchhooiicceeTTiimmeeoouutt
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.
-
DDiissppllaayyMMaannaaggeerr..ssoouurrcceeAAddddrreessss
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.
-
DDiissppllaayyMMaannaaggeerr..wwiilllliinngg
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 _W_i_l_l_i_n_g _t_o _m_a_n_a_g_e is
sent.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreessoouurrcceess
This resource specifies the name of the file to be loaded by _x_r_d_b
-
as the resource database onto the root window of screen 0 of the display.
The _X_s_e_t_u_p program, the Login widget, and _c_h_o_o_s_e_r 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
_/_e_t_c_/_X_1_1_/_x_d_m_/_X_r_e_s_o_u_r_c_e_s
is the conventional name.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..cchhoooosseerr
Specifies the program run to offer a host menu for Indirect queries
-
redirected to the special host name CHOOSER.
_/_u_s_r_/_X_1_1_R_6_/_l_i_b_e_x_e_c_/_c_h_o_o_s_e_r is the default.
See the sections XXDDMMCCPP AAcccceessss CCoonnttrrooll and CChhoooosseerr.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..xxrrddbb
Specifies the program used to load the resources. By default,
-
xdm
uses _/_u_s_r_/_X_1_1_R_6_/_b_i_n_/_x_r_d_b.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ccpppp
This specifies the name of the C preprocessor which is used by _x_r_d_b.
-
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..sseettuupp
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 _x_c_o_n_s_o_l_e here).
By default, no program is run. The conventional name for a
file used here is _X_s_e_t_u_p.
See the section SSeettuupp PPrrooggrraamm..
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssttaarrttuupp
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 _X_s_t_a_r_t_u_p.
See the section SSttaarrttuupp PPrrooggrraamm..
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..sseessssiioonn
This specifies the session to be executed (not running as root).
-
By default, _/_u_s_r_/_X_1_1_R_6_/_b_i_n_/_x_t_e_r_m is
run. The conventional name is _X_s_e_s_s_i_o_n.
See the section
Session Program.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreesseett
This specifies a program which is run (as root) after the session terminates.
-
By default, no program is run.
The conventional name is _X_r_e_s_e_t.
See the section
Reset Program.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ooppeennDDeellaayy
-
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ooppeennRReeppeeaatt
-
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ooppeennTTiimmeeoouutt
-
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssttaarrttAAtttteemmppttss
These numeric resources control the behavior of
-
xdm
when attempting to open intransigent servers. ooppeennDDeellaayy is
the length of the
pause (in seconds) between successive attempts, ooppeennRReeppeeaatt is the
number of attempts to make, ooppeennTTiimmeeoouutt 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 ssttaarrttAAtttteemmppttss is the number of times this entire process
is done before giving up on the server. After ooppeennRReeppeeaatt attempts have been made,
or if ooppeennTTiimmeeoouutt seconds elapse in any particular attempt,
xdm
terminates and restarts the server, attempting to connect again.
This
process is repeated ssttaarrttAAtttteemmppttss 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 ooppeennDDeellaayy, 5 for ooppeennRReeppeeaatt, 30 for ooppeennTTiimmeeoouutt and
4 for ssttaarrttAAtttteemmppttss.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ppiinnggIInntteerrvvaall
-
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ppiinnggTTiimmeeoouutt
To discover when remote displays disappear,
-
xdm
occasionally pings them, using an X connection and _X_S_y_n_c
calls. ppiinnggIInntteerrvvaall specifies the time (in minutes) between each
ping attempt, ppiinnggTTiimmeeoouutt specifies the maximum amount of time (in
minutes) to wait for the terminal to respond to the request. If the
terminal does not respond, the session is declared dead and terminated. By
default, both are set to 5 minutes. If you frequently use X terminals which
can become isolated from the managing host, you may wish to increase this
value. The only worry is that sessions will continue to exist after the
terminal has been accidentally disabled.
xdm
will not ping local displays. Although it would seem harmless, it is
unpleasant when the workstation session is terminated as a result of the
server hanging for NFS service and not responding to the ping.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..tteerrmmiinnaatteeSSeerrvveerr
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.''
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..uusseerrPPaatthh
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.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssyysstteemmPPaatthh
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.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssyysstteemmSShheellll
Xdm
-
sets the SHELL environment variable for the startup and reset scripts to the
value of this resource. It is _/_b_i_n_/_s_h by default.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ffaaiillssaaffeeCClliieenntt
If the default session fails to execute,
-
xdm
will fall back to this program. This program is executed with no
arguments, but executes using the same environment variables as
the session would have had (see the section SSeessssiioonn PPrrooggrraamm).
By default, _/_u_s_r_/_X_1_1_R_6_/_b_i_n_/_x_t_e_r_m is used.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ggrraabbSSeerrvveerr
-
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ggrraabbTTiimmeeoouutt
To improve security,
-
xdm
grabs the server and keyboard while reading the login name and password.
The
ggrraabbSSeerrvveerr 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 ggrraabbTTiimmeeoouutt resource specifies the maximum time
xdm
will wait for the grab to succeed. The grab may fail if some other
client has the server grabbed, or possibly if the network latencies
are very high. This resource has a default value of 3 seconds; you
should be cautious when raising it, as a user can be spoofed by a
look-alike window on the display. If the grab fails,
xdm
kills and restarts the server (if possible) and the session.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..aauutthhoorriizzee
-
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..aauutthhNNaammee
aauutthhoorriizzee is a boolean resource which controls whether
-
xdm
generates and uses authorization for the local server connections. If
authorization is used, aauutthhNNaammee is a list
of authorization mechanisms to use, separated by white space.
XDMCP connections dynamically specify which
authorization mechanisms are supported, so
aauutthhNNaammee is ignored in this case. When aauutthhoorriizzee 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, aauutthhoorriizzee
is ``true.'' aauutthhNNaammee is ``MIT-MAGIC-COOKIE-1,'' or, if
XDM-AUTHORIZATION-1 is available, ``XDM-AUTHORIZATION-1 MIT-MAGIC-COOKIE-1.''
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..aauutthhFFiillee
This file is used to communicate the authorization data from
-
xdm
to the server, using the --aauutthh 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.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..aauutthhCCoommppllaaiinn
If set to ``false,'' disables the use of the uunnsseeccuurreeGGrreeeettiinngg
-
in the login window.
See the section AAuutthheennttiiccaattiioonn WWiiddggeett..
The default is ``true.''
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreesseettSSiiggnnaall
The number of the signal _x_d_m sends to reset the server.
-
See the section CCoonnttrroolllliinngg tthhee SSeerrvveerr..
The default is 1 (SIGHUP).
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..tteerrmmSSiiggnnaall
The number of the signal _x_d_m sends to terminate the server.
-
See the section CCoonnttrroolllliinngg tthhee SSeerrvveerr..
The default is 15 (SIGTERM).
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreesseettFFoorrAAuutthh
The original implementation of authorization in the sample server reread the
-
authorization file at server reset time, instead of when checking the
initial connection. As
xdm
generates the authorization information just before connecting to the
display, an old server would not get up-to-date authorization information.
This resource causes
xdm
to send SIGHUP to the server after setting up the file, causing an
additional server reset to occur, during which time the new authorization
information will be read.
The default is ``false,'' which will work for all MIT servers.
-
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..uusseerrAAuutthhDDiirr
When
-
xdm
is unable to write to the usual user authorization file ($HOME/.Xauthority),
it creates a unique file name in this directory and points the environment
variable XAUTHORITY at the created file. It uses _/_t_m_p by default.
CONFIGURATION FILE
First, the
xdm
configuration file should be set up.
Make a directory (usually _/_e_t_c_/_X_1_1_/_x_d_m) to contain all
of the relevant files.
Here is a reasonable configuration file, which could be
named _x_d_m_-_c_o_n_f_i_g:
DisplayManager.servers: /etc/X11/xdm/Xservers
DisplayManager.errorLogFile: /var/log/xdm.log
DisplayManager*resources: /etc/X11/xdm/Xresources
DisplayManager*startup: /etc/X11/xdm/Xstartup
DisplayManager*session: /etc/X11/xdm/Xsession
DisplayManager.pidFile: /etc/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 RReessoouurrcceess section for a complete discussion.
XDMCP ACCESS CONTROL
The database file specified by the DDiissppllaayyMMaannaaggeerr..aacccceessssFFiillee provides
information which
xdm
uses to control access from displays requesting XDMCP service. This file
contains three types of entries: entries which control the response to
Direct and Broadcast queries, entries which control the response to
Indirect queries, and macro definitions.
The format of the Direct entries is simple, either a host name or a
pattern, which is distinguished from a host name by the inclusion of
one or more meta characters (`*' matches any sequence of 0 or more
characters, and `?' matches any single character) which are compared against
the host name of the display device.
If the entry is a host name, all comparisons are done using
network addresses, so any name which converts to the correct network address
may be used.
For patterns, only canonical host names are used
in the comparison, so ensure that you do not attempt to match
aliases.
Preceding either a host name or a pattern with a `!' character
causes hosts which
match that entry to be 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 xdm 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 _x_d_m run _c_h_o_o_s_e_r to offer a menu
of hosts to connect to. See the section CChhoooosseerr.
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 `\_n_e_w_l_i_n_e'
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
If compiled with IPv6 support, multicast address groups may also be included
in the list of addresses indirect queries are set to. Multicast addresses
may be followed by an optional / character and hop count. If no hop count is
specified, the multicast hop count defaults to 1, keeping the packet on the
local network. For IPv4 multicasting, the hop count is used as the TTL.
Examples:
rincewind.sample.net ff02::1 #IPv6 Multicast to ff02::1
#with a hop count of 1
ponder.sample.net CHOOSER 239.192.1.1/16 #Offer a menu of hosts
#who respond to IPv4 Multicast
# to 239.192.1.1 with a TTL of 16
CHOOSER
For X terminals that do not offer a host menu for use with Broadcast
or Indirect queries, the _c_h_o_o_s_e_r program can do this for them.
In the _X_a_c_c_e_s_s file, specify ``CHOOSER'' as the first entry in
the Indirect host list. _C_h_o_o_s_e_r will send a Query request to
each of the remaining host names in the list and offer a menu of all
the hosts that respond.
The list may consist of the word ``BROADCAST,'' in which case
_c_h_o_o_s_e_r will send a Broadcast instead, again offering a menu of
all hosts that respond. Note that on some operating systems, UDP
packets cannot be broadcast, so this feature will not work.
Example _X_a_c_c_e_s_s file using _c_h_o_o_s_e_r:
extract.lcs.mit.edu CHOOSER %HOSTS #offer a menu of these hosts
xtra.lcs.mit.edu CHOOSER BROADCAST #offer a menu of all hosts
The program to use for _c_h_o_o_s_e_r is specified by the
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..cchhoooosseerr resource. For more
flexibility at this step, the chooser could be a shell script.
_C_h_o_o_s_e_r is the session manager here; it is run instead of a
child _x_d_m to manage the display.
Resources for this program
can be put into the file named by
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreessoouurrcceess.
When the user selects a host, _c_h_o_o_s_e_r prints the host chosen,
which is read by the parent _x_d_m, and exits.
_x_d_m closes its connection to the X server, and the server resets
and sends another IInnddiirreecctt XDMCP request.
_x_d_m remembers the user's choice (for
DDiissppllaayyMMaannaaggeerr..cchhooiicceeTTiimmeeoouutt seconds) and forwards the request
to the chosen host, which starts a session on that display.
LISTEN
The following configuration directive is also defined for the Xaccess
configuration file:
-
LLIISSTTEENN _i_n_t_e_r_f_a_c_e _[_l_i_s_t _o_f _m_u_l_t_i_c_a_s_t _g_r_o_u_p _a_d_d_r_e_s_s_e_s_]
_i_n_t_e_r_f_a_c_e may be a hostname or IP addresss representing a
-
network interface on this machine, or the wildcard * to represent all
available network interfaces.
If one or more LISTEN lines are specified, xdm only listens for XDMCP
connections on the specified interfaces. If multicast group addresses
are listed on a listen line, xdm joins the multicast groups on the
given interface.
If no LISTEN lines are given, the original behavior of listening on
all interfaces is preserved for backwards compatibility.
Additionally, if no LISTEN is specified, xdm joins the default XDMCP
IPv6 multicast group, when compiled with IPv6 support.
To disable listening for XDMCP connections altogther, a line of LISTEN
with no addresses may be specified, or the previously supported method
of setting DisplayManager.requestPort to 0 may be used.
Examples:
LISTEN * ff02::1 # Listen on all interfaces and to the
# ff02::1 IPv6 multicast group.
LISTEN 10.11.12.13 # Listen only on this interface, as long
# as no other listen directives appear in
# file.
IPv6 MULTICAST ADDRESS SPECIFICATION
The Internet Assigned Numbers Authority has has assigned
ff0_X: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.) xdm defaults to listening on the
Link-Local scope address ff02:0:0:0:0:0:0:12b to most closely match the
old IPv4 subnet broadcast behavior.
LOCAL SERVER SPECIFICATION
The resource DDiissppllaayyMMaannaaggeerr..sseerrvveerrss gives a server specification
or, if the values starts with a slash (/), the name of a file
containing server specifications, one per line.
Each specification
indicates a display which should constantly be managed and which is
not using XDMCP.
This method is used typically for local servers only. If the resource
or the file named by the resource is empty, _x_d_m will offer XDMCP
service only.
Each specification consists of at least three parts: a display
name, a display class, a display type, and (for local servers) a command
line to start the server. A typical entry for local display number 0 would
be:
:0 Digital-QV local /usr/X11R6/bin/X :0
The display types are:
local local display: _x_d_m must run the server
foreign remote display: _x_d_m opens an X connection to a running server
The display name must be something that can be passed in the --ddiissppllaayy
option to an X program. This string is used to generate the display-specific
resource names, so be careful to match the
names (e.g., use ``:0 Sun-CG3 local /usr/X11R6/bin/X :0'' instead of
``localhost:0 Sun-CG3 local /usr/X11R6/bin/X :0''
if your other resources are specified as
``DisplayManager._0.session''). The display class portion is also used in the
display-specific resources, as the class of the resource. This is
useful if you have a large collection of similar displays (such as a corral of
X terminals) and would like to set resources for groups of them. When using
XDMCP, the display is required to specify the display class, so the manual
for your particular X terminal should document the display class
string for your device. If it doesn't, you can run
xdm
in debug mode and
look at the resource strings which it generates for that device, which will
include the class string.
When _x_d_m starts a session, it sets up authorization data for the
server. For local servers, _x_d_m passes
``--aauutthh _f_i_l_e_n_a_m_e'' on the server's command line to point
it at its authorization data.
For XDMCP servers, _x_d_m passes the
authorization data to the server via the AAcccceepptt XDMCP request.
RESOURCES FILE
The _X_r_e_s_o_u_r_c_e_s 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\
CtrlR: abort-display()\n\/&
F1: set-session-argument(failsafe) finish-field()\n\
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 ``: insert-char ()'' which responds to normal
typing).
This file may also contain resources for the setup program and _c_h_o_o_s_e_r.
SETUP PROGRAM
The _X_s_e_t_u_p 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 DDiissppllaayyMMaannaaggeerr..eexxppoorrttLLiisstt,
the following environment variables are passed:
DISPLAY the associated display name
PATH the value of DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssyysstteemmPPaatthh
SHELL the value of DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssyysstteemmSShheellll
XAUTHORITY may be set to an authority file
Note that since _x_d_m 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 DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ggrraabbSSeerrvveerr is set,
_X_s_e_t_u_p will not be able to connect
to the display at all.
Resources for this program
can be put into the file named by
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreessoouurrcceess.
Here is a sample _X_s_e_t_u_p 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 &
The authentication widget reads a name/password pair
from the keyboard. Nearly every imaginable
parameter can be controlled with a resource. Resources for this widget
should be put into the file named by
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreessoouurrcceess. All of these have reasonable
default values, so it is not necessary to specify any of them.
-
xxllooggiinn..LLooggiinn..wwiiddtthh,, xxllooggiinn..LLooggiinn..hheeiigghhtt,, xxllooggiinn..LLooggiinn..xx,, xxllooggiinn..LLooggiinn..yy
The geometry of the Login widget is normally computed automatically. If you
-
wish to position it elsewhere, specify each of these resources.
-
xxllooggiinn..LLooggiinn..ffoorreeggrroouunndd
The color used to display the typed-in user name.
-
-
xxllooggiinn..LLooggiinn..ffoonntt
The font used to display the typed-in user name.
-
-
xxllooggiinn..LLooggiinn..ggrreeeettiinngg
A string which identifies this window.
-
The default is ``X Window System.''
-
xxllooggiinn..LLooggiinn..uunnsseeccuurreeGGrreeeettiinngg
When X authorization is requested in the configuration file for this
-
display and none is in use, this greeting replaces the standard
greeting. The default is ``This is an unsecure session''
-
xxllooggiinn..LLooggiinn..ggrreeeettFFoonntt
The font used to display the greeting.
-
-
xxllooggiinn..LLooggiinn..ggrreeeettCCoolloorr
The color used to display the greeting.
-
-
xxllooggiinn..LLooggiinn..nnaammeePPrroommpptt
The string displayed to prompt for a user name.
-
Xrdb
strips trailing white space from resource values, so to add spaces at
the end of the prompt (usually a nice thing), add spaces escaped with
backslashes. The default is ``Login: ''
-
xxllooggiinn..LLooggiinn..ppaasssswwddPPrroommpptt
The string displayed to prompt for a password.
-
The default is ``Password: ''
-
xxllooggiinn..LLooggiinn..pprroommppttFFoonntt
The font used to display both prompts.
-
-
xxllooggiinn..LLooggiinn..pprroommppttCCoolloorr
The color used to display both prompts.
-
-
xxllooggiinn..LLooggiinn..ffaaiill
A message which is displayed when the authentication fails.
-
The default is ``Login incorrect''
-
xxllooggiinn..LLooggiinn..ffaaiillFFoonntt
The font used to display the failure message.
-
-
xxllooggiinn..LLooggiinn..ffaaiillCCoolloorr
The color used to display the failure message.
-
-
xxllooggiinn..LLooggiinn..ffaaiillTTiimmeeoouutt
The number of seconds that the failure message is displayed.
-
The default is 30.
-
xxllooggiinn..LLooggiinn..aalllloowwRRoooottLLooggiinn
If set to ``false'', don't allow root (and any other user with uid = 0) to
-
log in directly.
The default is ``true''.
-
xxllooggiinn..LLooggiinn..aalllloowwNNuullllPPaasssswwdd
If set to ``true'', allow an otherwise failing password match to succeed
-
if the account does not require a password at all.
The default is ``false'', so only users that have passwords assigned can
log in.
-
xxllooggiinn..LLooggiinn..ttrraannssllaattiioonnss
This specifies the translations used for the login widget. Refer to the X
-
Toolkit documentation for a complete discussion on translations. The default
translation table is:
CtrlH: delete-previous-character() \n\
CtrlD: delete-character() \n\
CtrlB: move-backward-character() \n\
CtrlF: move-forward-character() \n\
CtrlA: move-to-begining() \n\
CtrlE: move-to-end() \n\
CtrlK: erase-to-end-of-line() \n\
CtrlU: erase-line() \n\
CtrlX: erase-line() \n\
CtrlC: restart-session() \n\
Ctrl\\: abort-session() \n\
BackSpace:delete-previous-character() \n\
Delete: delete-previous-character() \n\
Return: finish-field() \n\
: insert-char() \
The actions which are supported by the widget are:
-
delete-previous-character
Erases the character before the cursor.
-
-
delete-character
Erases the character after the cursor.
-
-
move-backward-character
Moves the cursor backward.
-
-
move-forward-character
Moves the cursor forward.
-
-
move-to-begining
(Apologies about the spelling error.)
-
Moves the cursor to the beginning of the editable text.
-
move-to-end
Moves the cursor to the end of the editable text.
-
-
erase-to-end-of-line
Erases all text after the cursor.
-
-
erase-line
Erases the entire text.
-
-
finish-field
If the cursor is in the name field, proceeds to the password field; if the
-
cursor is in the password field, checks the current name/password pair. If
the name/password pair is valid, _x_d_m
starts the session. Otherwise the failure message is displayed and
the user is prompted again.
-
abort-session
Terminates and restarts the server.
-
-
abort-display
Terminates the server, disabling it. This action
-
is not accessible in the default configuration.
There are various reasons to stop _x_d_m on a system console, such as
when shutting the system down, when using _x_d_m_s_h_e_l_l,
to start another type of server, or to generally access the console.
Sending _x_d_m a SIGHUP will restart the display. See the section
CCoonnttrroolllliinngg XXDDMM.
-
restart-session
Resets the X server and starts a new session. This can be used when
-
the resources have been changed and you want to test them or when
the screen has been overwritten with system messages.
-
insert-char
Inserts the character typed.
-
-
set-session-argument
Specifies a single word argument which is passed to the session at startup.
-
See the section SSeessssiioonn PPrrooggrraamm.
-
allow-all-access
Disables access control in the server. This can be used when
-
the .Xauthority file cannot be created by
xdm.
Be very careful using this;
it might be better to disconnect the machine from the network
before doing this.
On some systems (OpenBSD) the user's shell must be listed in
/etc/shells
to allow login through xdm. The normal password and account expiration
dates are enforced too.
STARTUP PROGRAM
The _X_s_t_a_r_t_u_p program is run as
root when the user logs in.
It is typically a shell script.
Since it is run as root, _X_s_t_a_r_t_u_p should be
very careful about security. This is the place to put commands which add
entries to _/_e_t_c_/_u_t_m_p
(the _s_e_s_s_r_e_g program may be useful here),
mount users' home directories from file servers,
or abort the session if logins are not
allowed.
In addition to any specified by DDiissppllaayyMMaannaaggeerr..eexxppoorrttLLiisstt,
the following environment variables are passed:
DISPLAY the associated display name
HOME the initial working directory of the user
LOGNAME the user name
USER the user name
PATH the value of DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssyysstteemmPPaatthh
SHELL the value of DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..ssyysstteemmSShheellll
XAUTHORITY may be set to an authority file
No arguments are passed to the script.
Xdm
waits until this script exits before starting the user session. If the
exit value of this script is non-zero,
xdm
discontinues the session and starts another authentication
cycle.
The sample _X_s_t_a_r_t_u_p file shown here prevents login while the
file _/_e_t_c_/_n_o_l_o_g_i_n
exists.
Thus this is not a complete example, but
simply a demonstration of the available functionality.
Here is a sample _X_s_t_a_r_t_u_p script:
#!/bin/sh
#
# Xstartup
#
# This program is run as root after the user is verified
#
if [ -f /etc/nologin ]; then
xmessage -file /etc/nologin -timeout 30 -center
exit 1
fi
sessreg -a -l $DISPLAY -x /etc/X11/xdm/Xservers $LOGNAME
/etc/X11/xdm/GiveConsole
exit 0
SESSION PROGRAM
The _X_s_e_s_s_i_o_n program is the command which is run as the user's session.
It is run with
the permissions of the authorized user.
In addition to any specified by DDiissppllaayyMMaannaaggeerr..eexxppoorrttLLiisstt,
the following environment variables are passed:
DISPLAY the associated display name
HOME the initial working directory of the user
LOGNAME the user name
USER the user name
PATH the value of DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..uusseerrPPaatthh
SHELL the user's default shell (from _g_e_t_p_w_n_a_m)
XAUTHORITY may be set to a non-standard authority file
KRB5CCNAME may be set to a Kerberos credentials cache name
At most installations, _X_s_e_s_s_i_o_n should look in $HOME for
a file _._x_s_e_s_s_i_o_n_,
which contains commands that each user would like to use as a session.
_X_s_e_s_s_i_o_n should also
implement a system default session if no user-specified session exists.
See the section TTyyppiiccaall UUssaaggee.
An argument may be passed to this program from the authentication widget
using the `set-session-argument' action. This can be used to select
different styles of session. One good use of this feature is to allow
the user to escape from the ordinary session when it fails. This
allows users to repair their own _._x_s_e_s_s_i_o_n if it fails,
without requiring administrative intervention.
The example following
demonstrates this feature.
This example recognizes
the special
``failsafe'' mode, specified in the translations
in the _X_r_e_s_o_u_r_c_e_s file, to provide an escape
from the ordinary session. It also requires that the .xsession file
be executable so we don't have to guess what shell it wants to use.
#!/bin/sh
#
# Xsession
#
# This is the program that is run as the client
# for the display manager.
case $# in
1)
case $1 in
failsafe)
exec xterm -geometry 80x24-0-0
;;
esac
esac
startup=$HOME/.xsession
resources=$HOME/.Xresources
if [ -f "$startup" ]; then
exec "$startup"
else
if [ -f "$resources" ]; then
xrdb -load "$resources"
fi
twm &
xman -geometry +10-10 &
exec xterm -geometry 80x24+10+10 -ls
fi
The user's _._x_s_e_s_s_i_o_n file might look something like this
example. Don't forget that the file must have execute permission.
#! /bin/csh
# no -f in the previous line so .cshrc gets run to set $PATH
twm &
xrdb -merge "$HOME/.Xresources"
emacs -geometry +0+50 &
xbiff -geometry -430+5 &
xterm -geometry -0+50 -ls
RESET PROGRAM
Symmetrical with _X_s_t_a_r_t_u_p,
the _X_r_e_s_e_t script is run after the user session has
terminated. Run as root, it should contain commands that undo
the effects of commands in _X_s_t_a_r_t_u_p_, removing entries
from _/_e_t_c_/_u_t_m_p
or unmounting directories from file servers. The environment
variables that were passed to _X_s_t_a_r_t_u_p are also
passed to _X_r_e_s_e_t.
A sample _X_r_e_s_e_t script:
#!/bin/sh
#
# Xreset
#
# This program is run as root after the session ends
#
sessreg -d -l $DISPLAY -x /etc/X11/xdm/Xservers $LOGNAME
/etc/X11/xdm/TakeConsole
exit 0
CONTROLLING THE SERVER
Xdm
controls local servers using POSIX signals. SIGHUP is expected to reset the
server, closing all client connections and performing other cleanup
duties. SIGTERM is expected to terminate the server.
If these signals do not perform the expected actions,
the resources DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..rreesseettSSiiggnnaall and
DDiissppllaayyMMaannaaggeerr.._D_I_S_P_L_A_Y..tteerrmmSSiiggnnaall can specify alternate signals.
To control remote terminals not using XDMCP,
xdm
searches the window hierarchy on the display and uses the protocol request
KillClient in an attempt to clean up the terminal for the next session. This
may not actually kill all of the clients, as only those which have created
windows will be noticed. XDMCP provides a more sure mechanism; when
xdm
closes its initial connection, the session is over and the terminal is
required to close all other connections.
CONTROLLING XDM
Xdm
responds to two signals: SIGHUP and SIGTERM. When sent a SIGHUP,
xdm
rereads the configuration file, the access control file, and the servers
file. For the servers file, it notices if entries have been added or
removed. If a new entry has been added,
xdm
starts a session on the associated display. Entries which have been removed
are disabled immediately, meaning that any session in progress will be
terminated without notice and no new session will be started.
When sent a SIGTERM,
xdm
terminates all sessions in progress and exits. This can be used when
shutting down the system.
Xdm
attempts to mark its various sub-processes for
ps(1)
by editing the
command line argument list in place. Because
xdm
can't allocate additional
space for this task, it is useful to start
xdm
with a reasonably long
command line (using the full path name should be enough).
Each process which is
servicing a display is marked --_d_i_s_p_l_a_y_.
ADDITIONAL LOCAL DISPLAYS
To add an additional local display, add a line for it to the
_X_s_e_r_v_e_r_s file.
(See the section LLooccaall SSeerrvveerr SSppeecciiffiiccaattiioonn.)
Examine the display-specific resources in _x_d_m_-_c_o_n_f_i_g
(e.g., DDiissppllaayyMMaannaaggeerr..__00..aauutthhoorriizzee)
and consider which of them should be copied for the new display.
The default _x_d_m_-_c_o_n_f_i_g has all the appropriate lines for
displays ::00 and ::11.
OTHER POSSIBILITIES
You can use _x_d_m
to run a single session at a time, using the 4.3 _i_n_i_t
options or other suitable daemon by specifying the server on the command
line:
xdm -server ":0 SUN-3/60CG4 local /usr/X11R6/bin/X :0"
Or, you might have a file server and a collection of X terminals. The
configuration for this is identical to the sample above,
except the _X_s_e_r_v_e_r_s file would look like
extol:0 VISUAL-19 foreign
exalt:0 NCD-19 foreign
explode:0 NCR-TOWERVIEW3000 foreign
This directs
xdm
to manage sessions on all three of these terminals. See the section
CCoonnttrroolllliinngg XXddmm for a description of using signals to enable
and disable these terminals in a manner reminiscent of
init(8)
LIMITATIONS
One thing that
xdm
isn't very good at doing is coexisting with other window systems. To use
multiple window systems on the same hardware, you'll probably be more
interested in
xinit.
FILES
-
/etc/X11/xdm/xdm-config
-
the default configuration file
-
$HOME/.Xauthority
-
user authorization file where _x_d_m stores keys for clients to read
-
/usr/X11R6/libexec/chooser
-
the default chooser
-
/usr/X11R6/bin/xrdb
-
the default resource database loader
-
/usr/X11R6/bin/X
-
the default server
-
/usr/X11R6/bin/xterm
-
the default session program and failsafe client
-
/var/db/xdm/authdir/authfiles/A-
-
the default place for authorization files
-
/tmp/K5C
-
Kerberos credentials cache
SEE ALSO
X(7)
xinit(1)
xauth(1)
Xsecurity(7)
sessreg(1)
Xserver(1)
X Display Manager Control Protocol
AUTHOR
Keith Packard, MIT X Consortium