GDM
From GDM - GNOME Display Manager: "The GNOME Display Manager (GDM) is a program that manages graphical display servers and handles graphical user logins."
Display managers provide X Window System and Wayland users with a graphical login prompt.
Contents
Installation
GDM can be installed with the gdm package, and it is installed as part of the gnome group.
If you would prefer to use legacy GDM which was used in GNOME 2 and has its own configuration utility, install the gdm-oldAUR package. Note that the rest of this article discusses current GDM, not legacy GDM, unless indicated otherwise.
You might also wish to install the following:
- gdm3setup — An interface to configure GDM3, autologin options and change Shell theme
Starting
To start GDM at boot time enable gdm.service.
Autostarting applications
One might want to autostart certain commands, such as xrandr for instance, on login. This can be achieved by adding a command or script to a location that is sourced by the display manager. See Display manager#Autostarting for a list of supported locations.
/etc/gdm/Init directory is no longer a supported location, see [1].Configuration
Log-in screen background image
- Since GNOME 3.16, GNOME Shell themes are now stored as binary files (gresource).
- This change will be overwritten on subsequent updates of gnome-shell.
Firstly, you need to extract the existing GNOME Shell theme to a folder in your home directory. You can do this using the following script:
extractgst.sh
#!/bin/sh
gst=/usr/share/gnome-shell/gnome-shell-theme.gresource
workdir=${HOME}/shell-theme
for r in `gresource list $gst`; do
r=${r#\/org\/gnome\/shell/}
if [ ! -d $workdir/${r%/*} ]; then
mkdir -p $workdir/${r%/*}
fi
done
for r in `gresource list $gst`; do
gresource extract $gst $r >$workdir/${r#\/org\/gnome\/shell/}
done
Navigate to the created directory. You should find that the theme files have been extracted to it. Now copy your preferred background image to this directory.
Next, you need to create a file in the directory with the following content:
gnome-shell-theme.gresource.xml
<?xml version="1.0" encoding="UTF-8"?>
<gresources>
<gresource prefix="/org/gnome/shell/theme">
<file>calendar-arrow-left.svg</file>
<file>calendar-arrow-right.svg</file>
<file>calendar-today.svg</file>
<file>checkbox.svg</file>
<file>checkbox-focused.svg</file>
<file>checkbox-off.svg</file>
<file>checkbox-off-focused.svg</file>
<file>close-window.svg</file>
<file>close-window-active.svg</file>
<file>close-window-hover.svg</file>
<file>corner-ripple-ltr.png</file>
<file>corner-ripple-rtl.png</file>
<file>dash-placeholder.svg</file>
<file>gnome-shell.css</file>
<file>gnome-shell-high-contrast.css</file>
<file>icons/message-indicator-symbolic.svg</file>
<file>key-enter.svg</file>
<file>key-hide.svg</file>
<file>key-layout.svg</file>
<file>key-shift.svg</file>
<file>key-shift-latched-uppercase.svg</file>
<file>key-shift-uppercase.svg</file>
<file>noise-texture.png</file>
<file>filename</file>
<file>no-events.svg</file>
<file>no-notifications.svg</file>
<file>pad-osd.css</file>
<file>page-indicator-active.svg</file>
<file>page-indicator-checked.svg</file>
<file>page-indicator-hover.svg</file>
<file>page-indicator-inactive.svg</file>
<file>process-working.svg</file>
<file>toggle-off-hc.svg</file>
<file>toggle-off-intl.svg</file>
<file>toggle-off-us.svg</file>
<file>toggle-on-hc.svg</file>
<file>toggle-on-intl.svg</file>
<file>toggle-on-us.svg</file>
</gresource>
</gresources>
Replace filename with the filename of your background image.
Now, open the gnome-shell.css file in the directory and change the #lockDialogGroup definition as follows:
#lockDialogGroup {
background: #2e3436 url(filename);
background-size: [WIDTH]px [HEIGHT]px;
background-repeat: no-repeat;
}
Set background-size to the resolution that GDM uses, this might not necessarily be the resolution of the image. For a list of display resolutions see Display resolution. Again, set filename to be the name of the background image.
Finally, compile the theme using the following command:
$ glib-compile-resources gnome-shell-theme.gresource.xml
Then copy the resulting gnome-shell-theme.gresource file to the /usr/share/gnome-shell directory.
Then restart gdm.service (note that simply logging out is not enough) and you should find that it is using your preferred background image.
For more information, please see the following forum thread.
DConf configuration
Some GDM settings are stored in a DConf database. They can be configured either by adding keyfiles to the /etc/dconf/db/gdm.d directory and then recompiling the GDM database by running dconf update as root or by logging into the GDM user on the system and changing the setting directly using the gsettings command line tool. Note that for the former approach, a GDM profile file is required - this must be created manually as it is no longer shipped upstream, see below:
/etc/dconf/profile/gdm
user-db:user system-db:gdm file-db:/usr/share/gdm/greeter-dconf-defaults
For the latter approach, you can log into the GDM user with the command below:
# machinectl shell gdm@
Log-in screen logo
Either create the following keyfile
/etc/dconf/db/gdm.d/02-logo
[org/gnome/login-screen] logo='/path/to/logo.png'
and then recompile the GDM database or alternatively log in to the GDM user and execute the following:
$ gsettings set org.gnome.login-screen logo '/path/to/logo.png'
Changing the cursor theme
GDM disregards GNOME cursor theme settings and it also ignores the cursor theme set according to the XDG specification. To change the cursor theme used in GDM, either create the following keyfile
/etc/dconf/db/gdm.d/10-cursor-settings
[org/gnome/desktop/interface] cursor-theme='theme-name'
and then recompile the GDM database or alternatively log in to the GDM user and execute the following:
$ gsettings set org.gnome.desktop.interface cursor-theme 'theme-name'
Larger font for log-in screen
Click on the accessibility icon at the top right of the screen (a white circle with the silhouette of a person in the centre) and check the Large Text option.
To set a specific scaling factor, you can create the following keyfile:
/etc/dconf/db/gdm.d/03-scaling
[org/gnome/desktop/interface] text-scaling-factor='1.25'
and then recompile the GDM database or alternatively log in to the GDM user and execute the following:
$ gsettings set org.gnome.desktop.interface text-scaling-factor '1.25'
Turning off the sound
This tweak disables the audible feedback heard when the system volume is adjusted (via keyboard) on the login screen.
Either create the following keyfile:
/etc/dconf/db/gdm.d/04-sound
[org/gnome/desktop/sound] event-sounds='false'
and then recompile the GDM database or alternatively log in to the GDM user and execute the following:
$ gsettings set org.gnome.desktop.sound event-sounds 'false'
Configure power button behavior
- The logind settings for the power button are overriden by GNOME Settings Daemon. [2]
- As of GDM 3.18, the power button cannot be set to interactive. [3]
- In some cases, this setting will be ignored and hardcoded defaults will be used. [4]
Either create the following keyfile:
/etc/dconf/db/gdm.d/05-power
[org/gnome/settings-daemon/plugins/power] power-button-action='action'
and then recompile the GDM database or alternatively log in to the GDM user and execute the following:
$ gsettings set org.gnome.settings-daemon.plugins.power power-button-action 'action'
where action can be one of nothing, suspend or hibernate.
Enabling tap-to-click
Tap-to-click is disabled in GDM (and GNOME) by default, but you can easily enable it with a dconf setting.
To directly enable tap-to-click, use:
# sudo -u gdm gsettings set org.gnome.desktop.peripherals.touchpad tap-to-click true
If you prefer to do this with a GUI, use:
# sudo -u gdm dconf-editor
To check the if it was set correctly, use:
$ sudo -u gdm gsettings get org.gnome.desktop.peripherals.touchpad tap-to-click
If you get the error dconf-WARNING **: failed to commit changes to dconf: Error spawning command line, make sure dbus is running:
$ sudo -u gdm dbus-launch gsettings set org.gnome.desktop.peripherals.touchpad tap-to-click true
Disable/Enable Accessibility Menu
To disable or enable the Accessibility Menu, set the following key in dconf editor:
# machinectl shell gdm@ # gsettings set org.gnome.desktop.interface toolkit-accessibility false # exit
The menu is disabled when the key is false, enabled when it is true.
Keyboard layout
The system keyboard layout will be applied to GDM. See Keyboard configuration in Xorg#Using X configuration files.
If a system has multiple users, it is possible to specify a keyboard layout for GDM to use which is different from the system keyboard layout. Firstly, ensure the package gnome-control-center is installed. Then start gnome-control-center and navigate to Region & Language -> Input Sources. In the header bar, hit the Login Screen toggle button and then choose a keyboard layout from the list. Note that the Login Screen button will not be visible in the header bar unless multiple users are present on the system [5].
Users of GDM 2.x (legacy GDM) may need to edit ~/.dmrc as shown below:
~/.dmrc
[Desktop] Language=de_DE.UTF-8 # change to your default lang Layout=de nodeadkeys # change to your keyboard layout
Change the language
The system language will be applied to GDM. If a system has multiple users, it is possible to set a language for GDM different to the system language. In this case, firstly ensure that gnome-control-center is installed. Then, start gnome-control-center and choose Region & Language. In the header bar, check the Login Screen toggle button. Finally, click on Language and choose your language from the list. You will be prompted for your root password. Note that the Login Screen button will not be visible in the header bar unless multiple users are present on the system [6].
Users and login
Automatic login
To enable automatic login with GDM, add the following to /etc/gdm/custom.conf (replace username with your own):
/etc/gdm/custom.conf
# Enable automatic login for user [daemon] AutomaticLogin=username AutomaticLoginEnable=True
or for an automatic login with a delay:
/etc/gdm/custom.conf
[daemon] TimedLoginEnable=true TimedLogin=username TimedLoginDelay=1
You can set the session used for automatic login (replace gnome-xorg with desired session):
/var/lib/AccountsService/users/username
XSession=gnome-xorg
Passwordless login
If you want to bypass the password prompt in GDM then simply add the following line on the first line of /etc/pam.d/gdm-password:
auth sufficient pam_succeed_if.so user ingroup nopasswdlogin
Then, add the group nopasswdlogin to your system. See User group for group descriptions and group management commands.
Now, add your user to the nopasswdlogin group and you will only have to click on your username to login.
- Do not do this for a root account.
- You won't be able to change your session type at login with GDM anymore. If you want to change your default session type, you will first need to remove your user from the
nopasswdlogingroup.
Passwordless shutdown for multiple sessions
GDM uses polkit and logind to gain permissions for shutdown. You can shutdown the system when multiple users are logged in by setting:
/etc/polkit-1/localauthority.conf.d/org.freedesktop.logind.policy
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE policyconfig PUBLIC "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN" "http://www.freedesktop.org/standards/PolicyKit/1.0/policyconfig.dtd"> <policyconfig> <action id="org.freedesktop.login1.power-off-multiple-sessions"> <description>Shutdown the system when multiple users are logged in</description> <message>System policy prevents shutting down the system when other users are logged in</message> <defaults> <allow_inactive>yes</allow_inactive> <allow_active>yes</allow_active> </defaults> </action> </policyconfig>
You can find all available logind options (e.g. reboot-multiple-sessions) here.
Enable root login in GDM
It is not advised to login as root, but if necessary you can edit /etc/pam.d/gdm-password and add the following line before the line auth required pam_deny.so:
/etc/pam.d/gdm-password
auth sufficient pam_succeed_if.so uid eq 0 quiet
The file should look something like this:
/etc/pam.d/gdm-password
... auth sufficient pam_succeed_if.so uid eq 0 quiet auth sufficient pam_succeed_if.so uid >= 1000 quiet auth required pam_deny.so ...
You should be able to login as root after restarting GDM.
Hide user from login list
The users for the gdm user list are gathered by AccountsService. It will automatically hide system users (UID < 1000).
To hide ordinary users from the login list create or edit a file named after the user to hide in /var/lib/AccountsService/users/ to contain at least:
/var/lib/AccountsService/users/username
[User] SystemAccount=true
Setup default monitor settings
Some desktop environments store display settings in ~/.config/monitors.xml. xrandr commands are then generated on the base of the file content. GDM has a similar file stored in /var/lib/gdm/.config/monitors.xml.
If you have your monitors setup as you like (orientation, scaling, primary and so on) in ~/.config/monitors.xml and want GDM to honor those settings:
$ sudo cp ~/.config/monitors.xml /var/lib/gdm/.config/ $ sudo chown gdm:gdm /var/lib/gdm/.config/monitors.xml
The relevant parts of monitors.xml for screen rotation and scaling are:
<monitors version="2">
<configuration>
<logicalmonitor>
...
<scale>2</scale>
...
<transform>
<rotation>right</rotation>
<flipped>no</flipped>
</transform>
...
</logicalmonitor>
</configuration>
</monitors>
Changes will take effect on logout. This is necessary because GDM does not respect xorg.conf.
monitors.xml that was created under Wayland. See GDM bug 224 for more info. Alternatively, you can force GDM to #Use Xorg backend, and use a monitors.xml that was created under Xorg.Configure X server access permission
You can use the xhost command to configure X server access permissions.
For instance, to grant GDM the right to access the X server, use the following command:
# xhost +SI:localuser:gdm
Troubleshooting
Wayland and the proprietary NVIDIA driver
GDM doesn't work well in Wayland mode with the proprietary NVIDIA driver. When using this driver, GDM will use Xorg instead.[7]
Failure on logout
If GDM starts up properly on boot, but fails after repeated attempts on logout, try adding this line to the daemon section of /etc/gdm/custom.conf:
GdmXserverTimeout=60
Rootless Xorg
See Xorg#Rootless Xorg.
Use Xorg backend
The Wayland backend is used by default and the Xorg backend is used only if the Wayland backend cannot be started. As the Wayland backend has been reported to cause problems for some users, use of the Xorg backend may be necessary. To use the Xorg backend by default, edit the /etc/gdm/custom.conf file and uncomment the following line:
#WaylandEnable=false
GDM freezes with systemd
If GDM gets hang-up with systemctl enable gdm and systemctl start gdm works as expected, apply the config with systemctl edit gdm as below:
[Service] Type=idle
Incomplete removal of gdm
After removing gdm, systemd may report the following:
user 'gdm': directory '/var/lib/gdm' does not exist
To remove this warning, login as root and delete the primary user "gdm" and then delete the group "gdm":
# userdel gdm # groupdel gdm
Verify that gdm is successfully removed via pwck and grpck. To round it off, you may want to double-check no unowned files for gdm remain.
GDM auto-suspend (GNOME 3.28)
GDM uses a separate dconf database to control power management. You can make GDM behave the same way as user sessions by copying the user settings to GDM's dconf database.
$ IFS=$'\n'; for x in $(sudo -u username gsettings list-recursively org.gnome.settings-daemon.plugins.power); do eval "sudo -u gdm dbus-launch gsettings set $x"; done; unset IFS
where username is your user's name.
Or to simply disable auto-suspend (also run the command with ac replaced with battery to also disable it while running on battery):
$ sudo -u gdm dbus-launch gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type 'nothing'