The Configuration File - gdm.conf

Gnome Display Manager Reference Manual
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# The Configuration File - `gdm.conf`

The daemon and the accompanying utilities share a common configuration file: `etc/gdm/gdm.conf`.

The configuration file is divided into sections each containing variables that define the behaviour for a specific part of the GDM suite.

`gdm.conf` follows the standard GNOME configuration file syntax. Keywords in brackets define sections, strings before an equal sign (=) are variables and the data after equal sign represents their value.

## Daemon Configuration

[daemon]

AutomaticLoginEnable

      AutomaticLoginEnable=false

  If the user given in AutomaticLogin should be logged in upon first bootup. No password will be asked. This is useful for single user workstations where local console security is not an issue. Also could be useful for public terminals, although there see TimedLogin.

AutomaticLogin

      AutomaticLogin=

  This user should be automatically logged in on first bootup. AutomaticLoginEnable must be true and this must be a valid user for this to happen. "root" can never be autologged in however and gdm will just refuse to do it even if you set it up.

Chooser

      Chooser=bin/gdmchooser --disable-sound --disable-crash-dialog

  Full path and name of the chooser executable followed by optional arguments.

Configurator

      Configurator=/usr/bin/gdmconfig --disable-sound --disable-crash-dialog

  The pathname to the configurator binary. If the greeter ConfigAvailable option is set to true then run this binary when somebody chooses Configuration from the system menu. Of course GDM will first ask for root password however. And it will never allow this to happen from a remote display.

DefaultPath

      DefaultPath=/bin:/usr/bin:/usr/bin/X11:/usr/local/bin

  Specifies the path which will be set in the user's session.

DisplayInitDir

      DisplayInitDir=etc/gdm/Init

  Directory containing the display init scripts. See the ``Script Directories'' section for more info.

FailsafeXServer

      FailsafeXServer=

  An X command line in case we can't start the normal X server. should probably be some sort of a script that runs an appropriate low resolution server that will just work. This is tried before the XKeepsCrashing script is run.

GnomeDefaultSession

      GnomeDefaultSession=share/gnome/default.session

  The filename which GDM should read if there is no per user GNOME session file, and the user has requested the Gnome Chooser session.

Greeter

      Greeter=bin/gdmlogin --disable-sound --disable-crash-dialog

  Full path and name of the greeter executable followed by optional arguments.

Group

      Group=gdm

  The group id under which `gdmlogin`/`gdmchooser` are run.

HaltCommand

      HaltCommand=/sbin/shutdown -h now

  Full path and arguments to command to be executed when user selects Halt from the System menu.

KillInitClients

      KillInitClients=true

  Determines whether GDM should kill X clients started by the init scripts when the user logs in.

LogDir

      LogDir=var/gdm

  Directory containing the log files for the individual displays. By default this is the same as the ServAuthDir.

PidFile

      PidFile=var/run/gdm.pid

  Name of the file containing the `gdm` process id.

PostSessionScriptDir

      PostSessionScriptDir=etc/gdm/PostSession

  Directory containing the scripts run after the user logs out. See the ``Script Directories'' section for more info.

PreSessionScriptDir

      PreSessionScriptDir=etc/gdm/PreSession

  Directory containing the scripts run before the user logs in. See the ``Script Directories'' section for more info.

RebootCommand

      RebootCommand=/sbin/shutdown -r now

  Full path and optional arguments to the program to be executed when user selects Reboot from the System menu.

RootPath

      RootPath=/sbin:/usr/sbin:/bin:/usr/bin:/usr/bin/X11:/usr/local/bin

  Specifies the path which will be set in the root's session and the {Init,PreSession,PostSession} scripts executed by GDM.

ServAuthDir

      ServAuthDir=/var/gdm

  Directory containing the X authentication files for the individual displays. Should be owned by `gdm.gdm` with permissions 750.

SessionDir

      SessionDir=etc/gdm/Sessions

  Directory containing the scripts for all session types available on the system.

TimedLoginEnable

      TimedLoginEnable=false

  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. Note that no password will be asked for this user so you should be careful.

TimedLogin

      TimedLogin=

  This is the user that should be logged in after a specified number of seconds of inactivity. This can never be "root" and gdm will refuse to log in root this way.

TimedLoginDelay

      TimedLoginDelay=30

  This is the delay before the TimedLogin user will be logged in. It must be greater then or equal to 10.

User

      User=gdm

  The username under which `gdmlogin` / `gdmchooser` are run.

UserAuthDir

      UserAuthDir=

  The directory where user's `.Xauthority` file should be saved. When nothing is specfied the user's home directory is used.

UserAuthFBDir

      UserAuthFBDir=/tmp

  If GDM fails to update the user's `.Xauthority` file a fallback cookie is created in this directory.

UserAuthFile

      UserAuthFile=.Xauthority

  Name of the file used for storing user cookies.

XKeepsCrashing

      XKeepsCrashing=etc/gdm/XKeepsCrashing

  A script to run in case X keeps crashing. This is for running An X configuration. The first argument will be one of the programs specified in XKeepsCrashingConfigurators, the first one that exists. If none of those exist, this script will not be run. The second argument is a temporary filename that can be used for any purpose within the script. The rest of the arguments are translated messages. Please see the standard installed script for further details.

  In case FailsafeXServer is setup, that will be tried first. and this only used as a backup if even that server keeps crashing.

XKeepsCrashingConfigurators

      XKeepsCrashingConfigurators=/usr/bin/X11/XF86Setup /usr/bin/X11/Xconfigurator

  A list of programs to try which will do X configuration for the user. These are run from the XKeepsCrashing script. The first one on this list that exists is used.

## Security Options

[security]

AllowRoot

      AllowRoot=true

  Allow root (privilaged user) to log in through GDM. Set this to false if you want to disallow such logins.

  On systems that support PAM, this parameter is not as useful as you can use PAM to do the same thing, and in fact do even more. However it is still followed, so you should probably leave it true for PAM systems.

AllowRemoteRoot

      AllowRemoteRoot=true

  Allow root (privilaged user) to log in remotely through GDM. Set this to false if you want to disallow such logins. Remote logins are any logins that come in through the xdmcp.

  On systems that support PAM, this parameter is not as useful as you can use PAM to do the same thing, and in fact do even more. However it is still followed, so you should probably leave it true for PAM systems.

RelaxPermissions

      RelaxPermissions=0

  By default GDM ignores files and directories writable to other users than the owner.

  Changing the value of RelaxPermissions makes it possible to alter this behaviour:

  0 - Paranoia option. Only accepts user owned files and directories.

  1 - Allow group writable files and directories.

  2 - Allow world writable files and directories.

RetryDelay

      RetryDelay=3

  The number of seconds GDM should wait before reactivating the entry field after a failed login.

SessionMaxFile

      SessionMaxFile=524288

  GDM will refuse to read session files bigger than this number (specified in bytes). This can be bigger then UserMaxFile, since these are never read into memory, and so it is harder to "attack" gdm in this way.

  In addition to the size check both `gdm` and `gdmlogin` are extremely picky about accessing files in user directories. Neither will follow symlinks and they can optionally refuse to read files and directories writable by other than the owner. See the RelaxPermissions option for more info.

  However for the session files, GDM is not as picky. If you set RelaxPermissions to 0, GDM will assume it to be 1 for the case of session files. This is unfortunately because the session files would then never be able to be read in.

UserMaxFile

      UserMaxFile=65536

  GDM will refuse to read/write files bigger than this number (specified in bytes).

  In addition to the size check both `gdm` and `gdmlogin` are extremely picky about accessing files in user directories. Neither will follow symlinks and they can optionally refuse to read files and directories writable by other than the owner. See the RelaxPermissions option for more info.

VerboseAuth

      VerboseAuth=true

  Specifies whether GDM should print authentication errors in the message field in the greeter. Unlike in the past having this option be true is no longer a security risk. It will not specify if username or password was wrong, as both result in the same error. However it will give a different error when for example root login is disallowed and root logs in, or if a user with a disabled login tries to log in (only after the user succeeds). No verbose information about the login is given until a user is verified.

## XDCMP Support

[xdmcp]

DisplaysPerHost

      DisplaysPerHost=1

  To prevent attackers from filling up the pending queue, GDM will only allow one connection for each remote machine. If you want to provide display services to machines with more than one screen, you should increase the DisplaysPerHost value accordingly.

Enable

      Enable=false

  Setting this to true enables XDMCP support allowing remote displays/X terminals to be managed by GDM.

  `gdm` listens for requests on UDP port 177. See the Port option for more information.

  If GDM is compiled to support it, access from remote displays can be controlled using the TCP Wrappers library. The service name is `gdm`

  You should add

      		gdm:	.my.domain

  to your `/etc/hosts.allow`. See the `hosts_access(5)` man page for details.

  Please note that XDMCP is not a particularly secure protocol and that it is a good idea to block UDP port 177 on your firewall unless you really need it.

HonorIndirect

      HonorIndirect=true

  Enables XDMCP INDIRECT choosing (i.e. remote execution of `gdmchooser`) for X-terminals which don't supply their own display browser.

MaxPending

      MaxPending=4

  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.

MaxPendingIndirect

      MaxPendingIndirect=4

  GDM will only provide MaxPendingIndirect displays with host choosers simultaneously.

MaxSessions

      MaxSessions=16

  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.

MaxWait

      MaxWait=30

  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.

MaxWaitIndirect

      MaxWaitIndirect=30

  The MaxWaitIndirect parameter determines the maximum number of seconds between the time where a display requests a chooser and completion of protocol negotiation. If the timeout is exceeded, GDM will remove the display from the pending list freeing up the slot for other displays.

Port

      Port=177

  The UDP port number `gdm` should listen to for XDMCP requests. Don't change this unless you know what you're doing.

PingInterval

      PingInterval=5

  Interval in which to ping the X server in minutes. If the X server doesn't return 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.

## Common GUI Configuration Options

[gui]

Gtkrc

      Gtkrc=

  Path to a `gtkrc` containing the theme for use in `gdmlogin` / `gdmchooser`.

MaxIconWidth

      MaxIconWidth=128

  Specifies the maximum icon width (in pixels) that the face browser will display. Icons larger than this will be scaled.

MaxIconHeight

      MaxIconHeight=128

  Specifies the maximum icon height (in pixels) that the face browser will display. Icons larger than this will be scaled.

## Greeter Configuration

[greeter]

Browser

      Browser=true

  Set to true to enable the face browser. See the ``Greeter'' section for more information on the face browser.

ConfigAvailable

      ConfigAvailable=true

  Allow the configurator to be run from the greeter. Note that the user will need to type in the root password before the configurator is run however. See the Configurator option in the daemon section.

DefaultFace

      DefaultFace=share/pixmaps/nophoto.png

  Default icon file for users without a personal picture in `~/gnome/photo`. The image must be in an Imlib supported format and the file must be readable for the gdm user.

DefaultLocale

      DefaultLocale=english

  This language is used for the session unless nothing is specified in `~user/.gnome/gdm` and the user didn't select a language in the Locale menu in the greeter.

Exclude

      Exclude=bin,daemon,adm,lp,sync,shutdown,halt,mail,...

  Comma-separated list of usernames to exclude from the face browser. The excluded users will still be able to log in.

Font

      Font=-adobe-helvetica-bold-r-normal-*-*-180-*-*-*-*-*-*

  Font to use for the welcome message in the greeter.

GlobalFaceDir

      GlobalFaceDir=share/faces/

  Systemwide directory for face files. The sysadmin can place icons for users here without touching their homedirs. Faces are named after their users' logins.

  I.e. `<GlobalFaceDir>/johndoe` would contain the face icon for the user ``johndoe''. No image format extension should be specified.

  The face images must be stored in Imlib supported formats and they must be readable for the GDM user.

  A user's own icon file will always take precedence over the sysadmin provided one.

Icon

      Icon=share/pixmaps/gdm.xpm

  Icon to use for `gdmlogin` when it's in the iconified state. The image must be in an Imlib supported format and it must be readable for the GDM user. If no file is specified the iconify feature is disabled.

LocaleFile

      LocaleFile=etc/gdm/locale.alias

  File in GNU locale format with entries for all supported languages on the system.

Logo

      Logo=share/pixmaps/gnome-logo-large.png

  Image file to display in the logo box. The file must be in an Imlib supported format and it must be readable by the GDM user. If no file is specified the logo feature is disabled.

Quiver

      Quiver=true

  Controls whether `gdmlogin` should shake the display when an incorrect username/password is entered.

SystemMenu

      SystemMenu=false

  Turns the Shutdown/Halt menu on/off.

TitleBar

      TitleBar=true

  Display the title bar in the greeter.

Welcome

      Welcome=Welcome to %n

  Controls which text to display next to the logo image in the greeter. The following control chars are supported:

  %% the `%' character

  %d display's hostname

  %h Fully qualified hostname

  %m machine (processor type)

  %n Nodename (i.e. hostname without .domain)

  %r release (OS version)

  %s sysname (i.e. OS)

XineramaScreen

      XineramaScreen=0

  If the Xinerama extension is active the login window will be centered on this physical screen (use 0 for the first screen, 1 for the second..).

BackgroundColor

      BackgroundColor=#007777

  If the BackgroundType is 2, use this color in the background of the greeter. Also use it as the back of transparent images set on the background and if the BackgroundRemoteOnlyColor is set and this is a remote display.

BackgroundImage

      BackgroundImage=somefile.png

  If the BackgroundType is 1, then display this file as the bacground in the greeter.

BackgroundProgram

      BackgroundProgram=/usr/bin/xeyes

  If set this program will be run in the background while the login window is being displayed. Note that not all programs will run this way, since gdm does not usually have a home directory. You could set up home directory for the gdm user if you wish to run applications which require it.

BackgroundRemoteOnlyColor

      BackgroundRemoteOnlyColor=true

  On remote displays only set the color background. This is to make network load lighter. The BackgroundProgram is also not run.

BackgroundScaleToFit

      BackgroundScaleToFit=true

  Scale background image to fit the screen.

BackgroundType

      BackgroundType=2

  The type of background to set. 0 is none, 1 is image and 2 is color.

SetPosition

      SetPosition=true

  If true the position of the login window is determined by PositionX/PositionY.

PositionX

      PositionX=200

  The horizontal position of the login window.

PositionY

      PositionY=100

  The vertical position of the login window.

## XDCMP Chooser Options

[chooser]

DefaultHostImage

      DefaultHostImage=share/pixmaps/nohost.png

  File name for the default host icon. This image will be displayed if no icon is specified for a given host. The file must be in an Imlib supported format and it must be readable for the GDM user.

HostImageDir

      HostImageDir=share/hosts

  Repository for host icon files. The sysadmin can place icons for remote hosts here and they will appear in `gdmchooser`.

  The file name must match the fully qualified name (FQDN) for the host. The icons must be stored in Imlib supported formats and they must be readable to the gdm user.

ScanTime

      ScanTime=3

  Specifies how many seconds the chooser should wait for replies to its BROADCAST_QUERY.

## Local X Server Configuration

[servers]

0

      0=/usr/bin/X11/X

  Control section for local X servers. Each line indicates the local display number and the command that needs to be run to start the X server(s).

  GDM will append "`-auth <ServAuthDir>/:n.Xauth :n`", where n is the display number.

  On some systems it is necessary for gdm to know on which virtual consoles to run the X server. In this case, (if running XFree86) add "vt7" to the command line for example to run on virtual console 7.

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