.TH gdm 8 "28 Dec 2015"
.SH "NAME"
gdm \- GDM (GNOME Display Manager)
.SH "SYNOPSIS"
.PP
\fB/usr/sbin/gdm\fR [\fB--help\fR] [\fB--fatal-warnings\fR] [\fB--timed-exit\fR] [\fB--version\fR]
.SH "DESCRIPTION"
.PP
GDM is the GNOME Display Manager, a program used for login session management\&.
GDM supports managing the console display, other attached displays, XDMCP
displays, and flexible (or on-demand) displays\&.  Flexible displays make use
of the Virtual Terminals (VT) interfaces to allow user switching, so that
multiple users can run simultaneous sessions sharing the same console\&.
GDM uses ConsoleKit to manage what sessions are active on the system\&.
GDM supports a number of configuration interfaces which are described in
later sections of this manpage\&.
.PP
For each display that GDM is configured to manage, the
\fBgdm\fR program will launch a slave daemon which does the
work to actually manage the display\&.  The slave daemon will start the login
greeter GUI program, the program that the user interacts with\&.  Refer to the
"Login Greeter GUI" section below for more information about how the
user interface works\&.
.PP
If Virtual Terminals are supported on your system, you can start a flexible
display via the "User Switcher" panel applet\&.  You may need to add
this applet to your panel to make use of it\&.  You can also use the 
\fBgdmflexiserver\fR(1)
command to start flexible displays from the command line\&.
.PP
On Solaris, the GDM service is managed by the 
\fBsmf\fR(7)
service management facility under the service identifier
\fIsvc:/application/graphical-login/gdm\fR\&.
On Solaris, it is recommended that you use the
\fBsvcadm\fR(8) utility to enable and disable the
"gdm" service instead of killing the daemon with a SIGTERM signal.
.PP
GDM supports libaudit and Solaris auditing\&.  Refer to the 
"System Administration Guide: Security Services" and the
\fBaudit\fR(8) manpage for more information\&.
On Solaris, GDM also uses
\fBlogindevperm\fR(5)
to ensure that device permissions are set properly for the user on login\&.
.SH "OPTIONS"
.PP
The following options are supported by \fBgdm\fR:
.TP 30
.B --fatal-warnings
Make all warnings fatal\&.  Useful for debugging\&.
.TP 30
.B --help
Display detailed usage message\&.
.TP 30
.B --timed-exit
Exit after 30 seconds\&.  Useful for debugging\&.
.TP 30
.B --version
Display the GDM version\&.
.SH "ENVIRONMENT VARIABLES"
.PP
See
\fBenviron\fR(5)
for descriptions of environment variables\&.
.PP
When the following description refers to "scripts", these are
referring to the GDM \fBInit\fR, \fBPostLogin\fR,
\fBPreSession\fR, and \fBPostSession\fR scripts\&.
.TP 30
.B DESKTOP_SESSION
For any user session started by GDM, this environment variable is set to the
session name the user has chosen in the login GUI, such as "gnome" to
indicate that the \fB/usr/share/xsession/gnome\&.desktop\fR
session file was used to launch the session\&. 
.TP 30
.B DISPLAY
When running scripts and for any user session started by GDM, this environment
variable is set to the Xserver display value associated with the session\&.
.TP 30
.B DESKTOP_SESSION
For any user session started by GDM, this environment variable is set to the
keyboard layout that the user has chosen in the login GUI\&.
.TP 30
.B HOME
When running scripts and for any user session started by GDM, this environment
variable is set to the home directory associated with the user\&.
.TP 30
.B LANG
For any user session started by GDM, this environment variable is set to the
langauge choice selected when the user logged in\&.
.TP 30
.B REMOTE_HOST
When running scripts, this environment variable is set to the hostname if the
session is non-local (e\&.g\&. XDMCP)\&.
.TP 30
.B RUNNING_UNDER_GDM
When running scripts, this environment variable is set to "true", so
that they can identify when they are executed by the GDM process\&.
.TP 30
.B SHELL
When running scripts and for any user session started by GDM, this environment
variable is set to the shell associated with the session\&.
.TP 30
.B USER
When running scripts and for any user session started by GDM, this environment
variable is set to the username associated with the session\&.
.TP 30
.B USERNAME
When running scripts and for any user session started by GDM, this environment
variable is set to the username associated with the session\&.
.TP 30
.B XAUTHORITY
When running scripts and for any user session started by GDM, this environment
variable is set to the Xserver Xauthority file being used by the session\&.
.TP 30
.B XDG_SESSION_COOKIE
This environment variable is provided by ConsoleKit, and this value is set
for any user session started by GDM so that ConsoleKit can properly identify
the session\&.
.SH "EXTENDED DESCRIPTION"
.SS "Login Greeter GUI"
.PP
The login greeter GUI allows the user to specify how their user session should
be started and ensures that the user authenticates before gaining access to
their user session\&.  Authentication can be disabled if desired\&.
.PP
GDM makes use of
\fBpam\fR(3PAM)
to manage how the user authenticates (for example, by entering a username and
password, via a SmartCard, fingerprint reader, etc\&.)\&.  If authentication is
not desired, then GDM provides two configuration options which can be used
to bypass it: "Automatic Login" and "Timed Login"\&.  These
are not enabled by default, but can be turned on if desired\&.
.PP
The Automatic Login feature will cause GDM to bypass the login greeter GUI
entirely and immediately start a session for the user specified in the GDM
configuration\&.  The Timed Login feature will display the login greeter GUI for
a number of seconds specified in the GDM configuration\&.  If no user logs in
before the timeout, then GDM will automatically start the user session for the
user specified in the GDM configuration\&.  Timed Login is useful if you wish to
have the opportunity to login as a different user on some occasions\&.  Obviously
neither Automatic Login or Timed Login are secure, and they should only be used
on systems where the security provided by authentication is not needed\&.
.PP
GDM normally uses a PAM stack named "gdm"\&.  When Automatic Login or
Timed Login is enabled, then GDM instead uses a PAM stack named
"gdm-autologin"\&.  Note that Automatic Login and Timed Login will not
work properly if the "gdm-autologin" PAM stack is not defined in your
PAM configuration\&.
.PP
The login greeter GUI provides two mechanisms for specifying which user is
logging into the system\&.  Either the "Face Browser" can be used,
or GDM can prompt the user with the requests specified by the system PAM
configuration\&.  By default, this means entering both the username and password
by hand\&.
.PP
The Face Browser is designed to work when PAM is configured to allow users to
select their username, so it is not useful with certain PAM configurations
(such as when the username is identified via a SmartCard or fingerprint)\&.  The
Face Browser obviously exposes usernames to anyone with access to the machine,
so users may wish to disable it if this is considered a security issue\&.
.PP
When the Face Browser is enabled, a list of users will appear in the login
greeter GUI\&.  An icon for each user is shown, and users can specify what icon
is associated with their user\&.  If the user has an image file named
\fB~/\&.face\fR, then GDM will associate this image with the user\&.
If the user does not have such an image file, a default icon is displayed\&.
Image files must be no larger than 64K in size, or they are ignored by GDM\&.
.PP
The login greeter GUI can be configured to provide "Shutdown",
"Restart", and "Suspend" buttons which allow the user to
shutdown, restart, or suspend the system if desired\&.  On Solaris, the buttons
will only be available if the "solaris\&.system\&.shutdown" authorization name is
specified for the "gdm" user in the
\fB/etc/user_attr\fR file\&.  For example, the
\fB/etc/user_attr\fR file should include the following line to
make these buttons available from the GDM login GUI screen\&.
.PP
.nf
gdm::::type=normal;auths=solaris\&.system\&.shutdown
.fi
.PP
While the login greeter GUI is displayed, a panel is provided at the bottom
of the screen which provides useful information, interfaces that allow the
user to specify how their session should be started, and interfaces to help
the user navigate the login screen\&.  These include:
.sp
.in +2
\(bu
.mk
.in +3
.rt
A clock, showing the date and time\&.
.in -3
\(bu
.mk
.in +3
.rt
What type of session to run\&.
.in -3
\(bu
.mk
.in +3
.rt
An alternative language to use\&.
.in -3
\(bu
.mk
.in +3
.rt
An alternative keyboard layout (if supported)\&.
.in -3
\(bu
.mk
.in +3
.rt
The ability to launch assistive technology programs if desired\&.
.in -3
\(bu
.mk
.in +3
.rt
The ability to monitor the system battery (if using a system with a battery)\&.
.sp
.in -3
.in -2
.PP
The login greeter GUI also allows the user to take a screenshot\&.  If the
user presses the keybindng associated with printing the screen, then the
\fBgdm-screenshot\fR is run to take the screenshot\&.
.SS "Accessibility"
.PP
GDM supports accessibility\&.  Users can click on the accessibility icon on
the panel to specify which assistive programs should be launched with the
login GUI programs\&.  It is also possible to configure a system so that 
needed assistive programs should always be launched\&.
.SS "Security"
.PP
The GDM login GUI programs are run with a dedicated user id and group id\&.
By default "gdm" is used for both the user id and group id, but these
values are configurable\&.  The reason for using this special user and group is
to make sure that the GDM user interfaces run as a user without unnecessary
privileges, so that in the unlikely case that someone finds a weakness in the
GUI, they will not gain access to a privileged account on the machine\&.
.PP
Note that the GDM user and group do have some privileges beyond what a normal
user has\&.  This user and group has access to the Xserver authorization
directory which contains all of the Xserver authorization files and other
private information\&.  This means that someone who gains the GDM user/group
privileges can then connect to any running Xserver session\&.  Do not, under any
circumstances, make the GDM user/group a user/group that might be easy to get
access to, such as the user "\fBnobody\fR"\&.
.PP
File permissions are set on the authorization files so that only the user
has read and write access to ensure that users are unable to access the 
authorization files belonging to other users\&.
.SS "XDMCP"
.PP
XDMCP (X Display Manager Control Protocol) displays the login screen
and resulting session on a remote machine over the network interface\&.
By default, XDMCP is disabled in GDM\&.  However, GDM can be configured
to enable XDMCP so that users can log into the system from remote hosts\&.
By default, GDM listens to UDP port 177, although this can be configured\&.
GDM responds to QUERY and BROADCAST_QUERY requests by sending a WILLING
packet to the originator\&.
.PP
GDM provides configuration options that make GDM more resistant to
denial-of-service attacks on the XDMCP service\&.  The default values should
work for most systems, but several protocol parameters, handshaking timeouts,
and so on can be fine-tuned to make it more secure\&.  It is not recommended
that you modify the XDMCP configuration unless you know what you are doing\&.
.PP
GDM grants access to the hosts specified in the GDM service section of your
TCP Wrappers configuration file\&.  Refer to the \fBlibwrap\fR(3)
manpage for more information\&.  GDM does not support remote display access
control on systems without TCP Wrapper support\&.
.PP
GDM can also be configured to honor INDIRECT queries and present a host
chooser to the remote display\&. GDM remembers the user\&'s choice and forwards
subsequent requests to the chosen manager\&. GDM also supports an extension
to the protocol which makes GDM forget the redirection once the user\&'s
connection succeeds\&.  This extension is only supported if both daemons are
GDM\&. This extension is transparent and is ignored by XDM or other daemons
that implement XDMCP\&.
.PP
GDM only supports the MIT-MAGIC-COOKIE-1 authentication system\&. Because of
this, the cookies are transmitted as clear text\&. Therefore, you should be
careful about the network where you use this\&. That is, be careful about
where your XDMCP connection is going\&. Note that if snooping is possible, an
attacker could snoop your password as you log in, so a better XDMCP
authentication would not help you much anyway\&. If snooping is possible and
undesirable, you should use \fBssh\fR(1) for tunneling an X connection, rather
then using GDM\&'s XDMCP\&. Think of XDMCP as a sort of graphical telnet,
with the same security issues\&.
.SS "GDM Configuration"
.PP
ConsoleKit interfaces are used to configure how GDM should manage displays
in a multiseat environment, so to configure multiseat please refer to the
\fBconsole-kit-daemon\fR(8)
manpage\&.
.PP
GDM also provides a number of configuration interfaces which allow the user to
specify how GDM should operate\&.  The configuration available for the GDM
daemon and the GDM login greeter GUI are described below\&.  GDM also provides
scripting interfaces and other interfaces to configure how sessions are started
which are described in the "GDM Login Scripts and Session Files"
section of this manpage\&.
.PP
The default system configuration for the GDM daemon is stored in the file
\fB/etc/gdm/gdm\&.schemas\fR, and accessed by GDM via GConf\&.
Users are not recommended to modify this file since it may be overwritten on
upgrade\&.  Instead users should override these settings by specifying values
in the \fB/etc/gdm/custom\&.conf\fR file, which is in standard INI format\&.
.PP
The settings below are in "group/key=\fIdefault_value\fR \fItype\fR" format\&.
The type can be \fIstring\fR, \fIinteger\fR, or \fIboolean\fR\&.  To override
the "xdmcp/Enable" value, you would modify the
\fB/etc/gdm/custom\&.conf\fR so it contains these lines:
.PP
.nf
[xdmcp]
Enable=true
.fi
.PP
 
The following keys are supported for configuring the GDM daemon:
.sp
.ne 2
.mk
\fBchooser/Multicast=false (boolean)\fR
If true and IPv6 is enabled, the chooser will send a multicast query to the
local network and collect responses from the hosts who have joined multicast
group\&. 

.sp
.ne 2
.mk
\fBchooser/MulticastAddr=ff02::1 (string)\fR
This is the Link-local Multicast address\&.

.sp
.ne 2
.mk
\fBdaemon/TimedLoginEnable=false (boolean)\fR
If the user given in TimedLogin should be logged in after a number of seconds
(set with TimedLoginDelay) of inactivity on the login screen\&. This is useful
for public access terminals or perhaps even home use\&. If the user uses the
keyboard or browses the menus, the timeout will be reset to TimedLoginDelay or
30 seconds, whichever is higher\&. If the user does not enter a username but just
hits the ENTER key while the login program is requesting the username, then GDM
will assume the user wants to login immediately as the timed user\&. Note that no
password will be asked for this user so you should be careful, although if
using PAM it can be configured to require password entry before allowing login\&.

.sp
.ne 2
.mk
\fBdaemon/TimedLogin= (string)\fR
This is the user that should be logged in after a specified number of seconds
of inactivity\&.  If the value ends with a vertical bar | (the pipe symbol), then
GDM will execute the program specified and use whatever value is returned on
standard out from the program as the user\&. The program is run with the DISPLAY
environment variable set so that it is possible to specify the user in a
per-display fashion\&. For example if the value is
"/usr/bin/getloginuser|", then the program
\fB/usr/bin/getloginuser\fR will be run to get the user value\&. 

.sp
.ne 2
.mk
\fBdaemon/TimedLoginDelay=30 (integer)\fR
Delay in seconds before the TimedLogin  user will be logged in\&.

.sp
.ne 2
.mk
\fBdaemon/AutomaticLoginEnable=false (boolean)\fR
If true, the user given in AutomaticLogin  should be logged in immediately\&.
This feature is like timed login with a delay of 0 seconds\&.

.sp
.ne 2
.mk
\fBdaemon/AutomaticLogin= (string)\fR
This is the user that should be logged in immediately if AutomaticLoginEnable
is true\&.  If the value ends with a vertical bar | (the pipe symbol), then GDM
will execute the program specified and use whatever value is returned on
standard out from the program as the user\&. The program is run with the DISPLAY
environment variable set so that it is possible to specify the user in a
per-display fashion\&. For example if the value is
"/usr/bin/getloginuser|", then the program
\fB/usr/bin/getloginuser\fR will be run to get the user value\&. 

.sp
.ne 2
.mk
\fBdaemon/User=gdm (string)\fR
The username under which the greeter and other GUI programs are run\&.

.sp
.ne 2
.mk
\fBdaemon/Group=gdm (string)\fR
The group id used to run the login GUI programs

.sp
.ne 2
.mk
\fBdebug/Enable=false (boolean)\fR
If true, then GDM will provide debug output in the system log, which is
either \fB/var/log/messages\fR or
\fB/var/adm/messages\fR depending on your system\&.

.sp
.ne 2
.mk
\fBgreeter/IncludeAll=false (boolean)\fR
If true, then the face browser will show all users on the local machine\&. If
false, the face browser will only show users who have recently logged in\&.
.sp
When this key is true, GDM will call fgetpwent() to get a list of local users
on the system\&.  Anyusers with a user id less than 500 (or 100 if running on
Solaris) are filtered out\&.  The Face Browser also will display any users that
have previously logged in on the system (for example NIS/LDAP users)\&. It gets
this list via calling the
\fBck-history\fR(1)
ConsoleKit interface\&. It will also filter out any users which do not have a
valid shell (valid shells are any shell that getusershell() returns -
\fB/sbin/nologin\fR or \fB/bin/false\fR are
considered invalid shells even if getusershell() returns them)\&.
.sp
If false, then GDM more simply only displays users that have previously logged
in on the system (local or NIS/LDAP users) by calling the
\fBck-history\fR(1)
ConsoleKit interface\&.

.sp
.ne 2
.mk
\fBgreeter/Include= (string)\fR
Set to a list of users to always include in the Face Browser\&.  This value
is set to a list of users separated by commas\&.  By default, the value is
empty\&.

.sp
.ne 2
.mk
\fBgreeter/Exclude=bin,root,daemon,adm,lp,sync,shutdown,halt,mail,news,uucp,operator,nobody,nobody4,noaccess,postgres,pvm,rpm,nfsnobody,pcap (string)\fR
Set to a list of users to always exclude in the Face Browser\&.  This value
is set to a list of users separated by commas\&.  Note that the setting in the
\fBcustom\&.conf\fR overrides the default value, so if you wish
to add additional users to the list, then you need to set the value to the
default value with additional users appended to the list\&.

.sp
.ne 2
.mk
\fBgreeter/ShowLast=false (boolean)\fR
If true, then the session, language and layout dialogs in the login greeter GUI
will show the option "Last" by default\&.  The users default settings
in their \fB~/\&.dmrc\fR file will be used\&.  If no settings exist
in this file, then the system defaults will be used\&.  Note that GDM normally
caches the user\&'s \fB~/\&.dmrc\fR in the
\fB/var/cache/gdm\fR directory\&.  Turning on this feature causes
GDM to avoid using the cache, and instead accesses the user\&'s configuration
settings from their \fB~/\&.dmrc\fR file after
\fBpam_setcred\fR(3PAM) is called\&.
This feature is useful in situations where users might log into multiple
servers and the system administrator wants to avoid situations where the
user\&'s cached settings might become inconsistent across different servers\&.

.sp
.ne 2
.mk
\fBsecurity/DisallowTCP=false (boolean)\fR
If true, then always append "-\fBnolisten\fR tcp" to the
Xserver command line when starting attached Xservers, thus disallowing TCP
connection\&.  This is a more secure configuration if you are not using remote
connections\&.  Note that on Solaris, the
\fBoptions/tcp_listen\fR property of the 
\fBx11-server\fR service also controls whether this option is
appended to the Xserver command line\&.  The GDM configuration value is set to
"false" by default on Solaris to defer control of this feature to
this \fBx11-server\fR property\&.  Refer to the
\fBXserver\fR(1)
manpage for more information\&.

.sp
.ne 2
.mk
\fBxdmcp/DisplaysPerHost=1 (integer)\fR
To prevent attackers from filling up the pending queue, GDM will only allow
one connection for each remote computer\&. If you want to provide display
services to computers with more than one seat, you should increase this
value\&.  Note that the number of attached DISPLAYS allowed is not limited\&.
Only remote connections via XDMCP are limited by this configuration option\&. 

.sp
.ne 2
.mk
\fBxdmcp/Enable=false (boolean)\fR
Setting this to true enables XDMCP support allowing remote displays/X terminals
to be managed by GDM\&.  If GDM is compiled to support it, access from remote
displays can be controlled using the TCP Wrappers library\&.

.sp
.ne 2
.mk
\fBxdmcp/HonorIndirect=true (boolean)\fR
Enables XDMCP INDIRECT choosing for X-terminals which do not supply their own
display browser\&. 

.sp
.ne 2
.mk
\fBxdmcp/MaxPending=4 (integer)\fR
To avoid denial of service attacks, GDM has fixed size queue of pending
connections\&. Only MaxPending displays can start at the same time\&.  Please
note that this parameter does not limit the number of remote displays which
can be managed\&. It only limits the number of displays initiating a
connection simultaneously\&. 

.sp
.ne 2
.mk
\fBxdmcp/MaxSessions=16 (integer)\fR
Determines the maximum number of remote display connections which will be
managed simultaneously\&. I\&.e\&. the total number of remote displays that
can use your host\&. 

.sp
.ne 2
.mk
\fBxdmcp/MaxWait=30 (integer)\fR
When GDM is ready to manage a display an ACCEPT packet is sent to it
containing a unique session id which will be used in future XDMCP
conversations\&.  GDM will then place the session id in the pending queue
waiting for the display to respond with a MANAGE request\&.  If no response
is received within MaxWait seconds, GDM will declare the display dead and
erase it from the pending queue freeing up the slot for other displays\&. 

.sp
.ne 2
.mk
\fBxdmcp/MaxWaitIndirect=30 (integer)\fR
The MaxWaitIndirect parameter determines the maximum number of seconds between
the time where a user chooses a host and the subsequent indirect query where
the user is connected to the host\&. When the timeout is exceeded, the
information about the chosen host is forgotten and the indirect slot freed up
for other displays\&. The information may be forgotten earlier if there are more
hosts trying to send indirect queries then MaxPendingIndirect\&. 

.sp
.ne 2
.mk
\fBxdmcp/PingIntervalSeconds=15 (integer)\fR
Interval in which to ping the Xserver in seconds\&. If the Xserver does not
respond before the next time we ping it, the connection is stopped and the
session ended\&. This is a combination of the XDM PingInterval and PingTimeout,
but in seconds\&. 

.sp
.ne 2
.mk
\fBxdmcp/Port=177 (integer)\fR
The UDP port number gdm should listen to for XDMCP requests\&.

.sp
.ne 2
.mk
\fBxdmcp/Willing=/etc/gdm/Willing (string)\fR
When the machine sends a WILLING packet back after a QUERY it sends a string
that gives the current status of this server\&. The default message is the
system ID, but it is possible to create a script that displays customized
message\&.  If this script does not exist or this key is empty the default
message is sent\&.  If this script succeeds and produces some output, the
first line of it\&'s output is sent (and only the first line)\&. It runs at
most once every 3 seconds to prevent possible denial of service by flooding
the machine with QUERY packets\&. 

.PP
The default system configuration for the GDM login greeter GUI is stored in
the system GConf schemas directory in the file
\fBgdm-simple-greeter\&.schemas\fR, and accessed by GDM via
GConf\&.  Users are not recommended to modify this file file since it may be
overwritten on upgrade\&.  Instead users should override these settings by
modifying the GConf configuration for the GDM user (the user specified in the
Daemon/User configuration key above), normally the "gdm" user\&.
Users can use the 
\fBgconftool-2\fR(1)
or
\fBgconf-editor\fR(1)
programs to set these values, if desired\&.  Refer to the EXAMPLES section of
this manpage for more information about how to use these tools to change
common settings\&.
.PP
GDM will use the GCONF_DEFAULT_SOURCE_PATH environment variable to ensure that each display uses it\&'s own GConf configuration\&.  This way changes in GConf will only affect the greeter in a per-seat manner\&.
.PP
 
The following keys are supported for configuring the GDM login greeter GUI and
are in
"GConf key=\fIdefault_value\fR
(\fIgconf_data_type\fR)"
format:
.sp
.ne 2
.mk
\fB/apps/gdm/simple-greeter/banner_message_enable=false (boolean)\fR
Controls whether the banner message text is displayed\&. 

.sp
.ne 2
.mk
\fB/apps/gdm/simple-greeter/banner_message_text=NULL (string)\fR
Specifies the text banner message to show on the greeter window\&.

.sp
.ne 2
.mk
\fB/apps/gdm/simple-greeter/disable_restart_buttons=false (boolean)\fR
Controls whether to show the restart buttons in the login window\&.

.sp
.ne 2
.mk
\fB/apps/gdm/simple-greeter/disable_user_list=true (boolean)\fR
If true, then the face browser with known users is not shown in the login
window\&. 

.sp
.ne 2
.mk
\fB/apps/gdm/simple-greeter/logo_icon_name=computer (string)\fR
Set to the themed icon name to use for the greeter logo\&.

.sp
.ne 2
.mk
\fB/apps/gdm/simple-greeter/wm_use_compiz=false (boolean)\fR
Controls whether compiz is used as the window manager instead of metacity\&.

.sp
.ne 2
.mk
\fB/desktop/gnome/interface/accessibility=true (boolean)\fR
Controls whether the Accessibility infrastructure will be started with the GDM
GUI\&. This is needed for many accessibility technology programs to work\&. 

.sp
.ne 2
.mk
\fB/desktop/gnome/applications/at/screen_magnifier_enabled=false (boolean)\fR
If set, then the assistive tools linked to this GConf key will be started with
the GDM GUI program\&. By default this is a screen magnifier application\&. 

.sp
.ne 2
.mk
\fB/desktop/gnome/applications/at/screen_keyboard_enabled=false (boolean)\fR
If set, then the assistive tools linked to this GConf key will be started with
the GDM GUI program\&. By default this is an on-screen keyboard application\&. 

.sp
.ne 2
.mk
\fB/desktop/gnome/applications/at/screen_reader_enabled=false (boolean)\fR
If set, then the assistive tools linked to this GConf key will be started with
the GDM GUI program\&. By default this is a screen reader application\&. 

.PP
On Solaris, GDM also supports the CONSOLE, PASSREQ, PATH, and SUPATH
configuration options in \fB/etc/default/login\fR\&.  Refer to the
\fBlogin\fR(1) manpage for details\&.
.SS "Logging"
.PP
GDM logs error and debug information to the system syslog file\&.
.PP
Output from the Xservers started by GDM is stored in the GDM log directory,
\fB/var/log/gdm\fR\&.  The Xserver output for each display is
saved in a file \fB\fIdisplay\fR\&.log\fR,
where \fIdisplay\fR is the DISPLAY value for the
associated display\&.
.PP
Output from the GDM login greeter GUI is saved in a file
\fB\fIdisplay\fR-greeter\&.log\fR and
output from the GDM slave daemon is saved in a file
\fB\fIdisplay\fR-slave\&.log\fR\&.  Again,
the \fIdisplay\fR is the DISPLAY value for the
associated display\&.
.PP
Four older versions of each file are also stored, by appending 1 through 4 to
the filename\&. These files are rotated, as new sessions on that display are
started\&.
.PP
The output from the user session is saved in a file
\fB~/\&.xsession-errors\fR\&.  The user session output is 
redirected before the \fBPreSession\fR script is started\&.
.PP
Note that if the session is a failsafe session, or if GDM cannot open this file
for some reason, a fallback file is created named
\fB/tmp/xses-\fIuser\fR\&.XXXXXX\fR,
where XXXXXX are random characters\&.
.PP
If you run a system with quotas set, consider using the PostSession script to
delete the \fB~/\&.xsession-errors\fR file, so that this log file
is not stored unnecessarily\&.
.SH "EXAMPLES"
.PP
Note that the user should change user to the "gdm" user before
running the following
\fBgconftool-2\fR(1) commands\&.  For example, the
 \fBsu\fR(8)
command could be used\&.  Configuration changes will only take effect if they
apply to the "gdm" user\&.
.PP
\fBExample 1: To Enable Face Browser for all GDM login greeter GUI\fR
.PP
.PP
.nf
\fBexample% gconftool-2 --direct --config-source xml:readwrite:/var/lib/gdm/\&.gconf\&.mandatory -t bool -s /apps/gdm/simple-greeter/disable_user_list false\fR
.fi
.PP
\fBExample 2: To Change the Background Image to \fBstream\&.jpg\fR for the GDM login greeter GUI\fR
.PP
.PP
.nf
\fBexample% gconftool-2 --direct --config-source xml:readwrite:/var/lib/gdm/\&.gconf\&.mandatory -t string -s /desktop/gnome/background/picture_filename /usr/share/pixmaps/backgrounds/opensolaris/stream\&.jpg\fR
.fi
.PP
\fBExample 3: To Disable Face Browser for StaticSeat1 GDM login greeter GUI\fR
.PP
.PP
.nf
\fBexample% gconftool-2 --direct --config-source xml:readwrite:/var/lib/gdm/StaticSeat1/\&.gconf -t bool -s /apps/gdm/simple-greeter/disable_user_list true\fR
.fi
.SH "EXIT STATUS"
.PP
The following exit values are returned:
.TP 8
.B 0
Application exited successfully
.TP 8
.B >0
Application exited with failure
.SH "FILES"
.PP
The following files are used by this application:
.TP 30
.B /usr/sbin/gdm
Executable for GNOME Display Manager\&.

.SS "GDM Login Scripts and Session Files"
.PP
The following GDM login integration interfaces are discussed below:
.sp
.in +2
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/Init/Default\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/Init/\fIdisplay\fR\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/PostLogin/Default\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/PostLogin/\fIdisplay\fR\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/PreSession/Default\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/PreSession/\fIdisplay\fR\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/Xsession\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/X11/xinit/xinitrc\&.d\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/profile\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB~/profile\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/X11/xinit/xinitrc\&.d\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/PostSession/Default\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/etc/gdm/PostSession/\fIdisplay\fR\fR
.in -3
.in -2
.PP
The following session files are also discussed below:
.sp
.in +2
\(bu
.mk
.in +3
.rt
\fB/usr/share/gdm/autostart/LoginWindow/*\&.desktop\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB/usr/share/xsessions/*\&.desktop\fR
.in -3
\(bu
.mk
.in +3
.rt
\fB~/\&.dmrc\fR(default user session)
.in -3
.in -2
.PP
The \fBInit\fR, \fBPostLogin\fR,
\fBPreSession\fR, and \fBPostSession\fR scripts
all work as described below\&. 
.PP
For each type of script, the default one which will be executed is called
"Default" and is stored in a directory associated with the script
type\&. So the default \fBInit\fR script is
\fB/etc/gdm/Init/Default\fR\&.  A per-display script can be
provided, and if it exists it will be run instead of the default script\&. Such
scripts are stored in the same directory as the default script and have the
same name as the Xserver DISPLAY value for that display\&. For example, if the
/etc/gdm/Init/:0  script exists, it will be run for
DISPLAY ":0"\&.
.PP
All of these scripts are run with root privilege and return 0 if run
successfully, and a non-zero return code if there was any failure that should
cause the login session to be aborted\&. Also note that GDM will block until the
scripts finish, so if any of these scripts hang, this will cause the login
process to also hang\&.
.PP
When the Xserver for the login GUI has been successfully started, but before
the login GUI is actually displayed, GDM will run the \fBInit\fR
script\&. This script is useful for starting programs that should be run while
the login screen is showing, or for doing any special initialization if
required\&.
.PP
After the user has been successfully authenticated GDM will run the
\fBPostLogin\fR script\&. This is done before any session setup
has been done, including before the 
\fBpam_open_session\fR(3PAM)
call\&. This script is useful for doing any session initialization that needs to
happen before the session starts\&. For example, you might setup the user\&'s
$HOME directory if needed\&.
.PP
After the user session has been initialized, GDM will run the
\fBPreSession\fR script\&. This script is useful for doing any
session initialization that needs to happen after the session has been
initialized\&. It can be used for session management or accounting, for example\&.
.PP
When a user terminates their session, GDM will run the
\fBPostSession\fR script\&. Note that the Xserver will have been
stopped by the time this script is run, so it should not be accessed\&.
.PP
Note that the \fBPostSession\fR script will be run even when the
display fails to respond due to an I/O error or similar\&. Thus, there is no
guarantee that X applications will work during script execution\&.
.PP
All of the above scripts will set the RUNNING_UNDER_GDM environment variable
to "yes"\&. If the scripts are also shared with other display managers,
this allows you to identify when GDM is calling these scripts, so you can run
specific code when GDM is used\&. 
.PP
The \fB/usr/share/gdm/autostart/LoginWindow\fR directory
contains \fB\&.desktop\fR files\&.  Any
\fB\&.desktop\fR files in this directory will cause the
associated program to automatically start with the login GUI greeter\&. By
default, GDM is shipped with files which will autostart the gdm-simple-greeter
login GUI greeter itself, the \fBgnome-power-manager\fR
application, the \fBgnome-settings-daemon\fR, and the
\fBmetacity\fR window manager\&. These programs are needed for the
greeter program to work\&. In addition, desktop files are provided for starting
various AT programs if the associated accessibility configuration GConf keys
are set\&.
.PP
The administrator can customize \&.desktop files\&. For example, an \fBxterm\&.desktop\fR file can be useful when debugging the GDM login greeter\&. A \&.desktop file to launch \fBxterm\fR(1) would look as follows: 
.PP
.nf
[Desktop Entry] 
Name=Xterm 
Comment=Xterm 
Exec=/usr/X11/bin/xterm 
OnlyShowIn=GNOME; 
Terminal=false 
Type=Application 
X-GNOME-Autostart-Phase=Applications 
X-GNOME-AutoRestart=true 
.fi
.PP
The user\&'s default session and language choices are stored in the
\fB~/\&.dmrc\fR file\&. When a user logs in for the first time, this
file is created with the user\&'s initial choices\&. The user can change these
default values by simply changing to a different value when logging in\&. GDM
will remember this change for subsequent logins\&. 
.PP
The session types which are available in the GDM login greeter GUI are
specified by \fB\&.desktop\fR files\&.  These desktop files are in
standard INI format and the executable that will be run to start the session
is specified by the "Exec" key in the file\&.  Desktop files are
normally stored in the \fB/usr/share/xsessions\fR directory\&.
However, GDM will search for desktop files in the following directories in this
order: \fB/etc/X11/sessions/\fR,
\fB/etc/dm/Sessions\fR,
\fB/usr/share/xsessions\fR, and
\fB/usr/share/gdm/BuiltInSessions\fR\&.
.PP
The \fB/etc/gdm/Xsession\fR script is called between the
\fBPreSession\fR and the \fBPostSession\fR
scripts\&. This script does not support per-display like the other scripts\&. This
script is used for actually starting the user session\&. This script is run as
the user, and it will run whatever session was specified by the Desktop session
file the user selected to start\&.  The \fB/etc/gdm/Xsession\fR
script will source \fB/etc/profile\fR,
\fB~/\&.profile\fR, and all scripts in the
\fB/etc/X11/xinit/xinitrc\&.d\fR directory before starting the
user session\&.  Refer to the
\fBprofile\fR(4)
manpage for more information\&.
.SS "Configuration Files"
.TP 30
.B /etc/gdm/gdm\&.schemas\fR\fR
GDM default daemon configuration\&.

.TP 30
.B /etc/gdm/custom\&.conf\fR\fR
GDM daemon configuration customization\&.

.TP 30
.B /etc/gconf/schemas/gdm-simple-greeter\&.schemas\fR\fR
GDM default login greeter GUI configuration\&.

.TP 30
.B /etc/default/login\fR\fR
On Solaris, GDM supports the CONSOLE, PASSREQ, PATH, and SUPATH configuration
options\&.  Refer to the
\fBlogin\fR(1)
manpage for details\&.

.TP 30
.B ~gdm/\&.gconf\&.mandatory\fR\fR
The GDM user\&'s mandatory GConf settings\&.

.TP 30
.B ~gdm/\&.gconf\fR\fR
The GDM user\&'s GConf settings\&.

.TP 30
.B ~gdm/\fIseat\fR/\&.gconf\fR\fR
The per-seat GDM user\&'s GConf settings\&.

.TP 30
.B ~gdm/\&.gconf\&.path\fR\fR
This file specifies the GDM user\&'s mandatory GConf settings directory\&.

.SS "Logging"
.TP 30
.B /var/log/gdm/\fIdisplay\fR\&.log\fR\fR
Xserver output for each \fIdisplay\fR\&.

.TP 30
.B /var/log/gdm/\fIdisplay\fR-greeter\&.log\fR\fR
GDM login greeter GUI output for each \fIdisplay\fR\&.

.TP 30
.B /var/log/gdm/\fIdisplay\fR-slave\&.log\fR\fR
GDM slave daemon output for each \fIdisplay\fR\&.

.TP 30
.B ~/\&.xsession-errors\fR\fR
Output from the user session\&.

.SS "GDM Xauthority files"
.TP 30
.B /var/run/gdm\fR\fR
Stores the Xserver authentication files for each managed session\&.

.SS "Face Browser"
.TP 30
.B /usr/share/pixmaps/faces\fR\fR
Global directory for face images\&.

.TP 30
.B ~/\&.face\fR\fR
User-defined icon to be used by GDM face browser\&.

.SS "GDM user cache"
.TP 30
.B /var/cache/gdm\fR\fR
GDM copies the user\&'s \fB~/\&.dmrc and
\fB~/\&.face\fR files to
\fB/var/cache/gdm/\fIusername\fR\fR, so
that they can be accessed on subsequent logins without accessing the user\&'s
$HOME directory before 
\fBpam_setcred\fR(3PAM) is called\&.\fR

.SH "SEE ALSO"
.PP
More information can be found at:
.PP
\fBhttp://library\&.gnome\&.org/admin/gdm\fR
.PP
Latest version of the \fIGNOME Desktop User Guide\fR for your
platform\&.
.PP
\fBgdmflexiserver\fR(1),
\fBgdm-screenshot\fR(1),
\fBgconftool-2\fR(1),
\fBgconf-editor\fR(1),
\fBlogin\fR(1),
\fBssh\fR(1),
\fBXorg\fR(1),
\fBXserver\fR(1),
\fBaudit\fR(8),
\fBconsole-kit-daemon\fR(8),
\fBsvcadm\fR(8),
\fBlibwrap\fR(3),
\fBpam\fR(3PAM),
\fBlogindevperm\fR(5),
\fBpam\&.conf\fR(5),
\fBprofile\fR(5),
\fBuser_attr\fR(5),
\fBattributes\fR(7),
\fBenviron\fR(7),
\fBsmf\fR(7)
.SH "NOTES"
.PP
This man page written by Martin K\&. Petersen <mkp@mkp\&.net>, George Lebl
<jirka@5z\&.com>, and Brian Cameron <brian\&.cameron@sun\&.com>\&.
Copyright (c) 1998, 1999 by Martin K\&. Petersen\&.
Copyright (c) 2001, 2003, 2004 by George Lebl\&.
Copyright (c) 2003 by Red Hat, Inc\&.
Copyright (c) 2006, 2016, Oracle and/or its affiliates. All rights reserved.