LightDM

LightDM is a cross-desktop display manager. Its key features are:

Cross-desktop - supports different desktop technologies.
Supports different display technologies (X, Mir, Wayland ...).
Lightweight - low memory usage and high performance.
Supports guest sessions.
Supports remote login (incoming - XDMCP, VNC, outgoing - XDMCP, PAM).
Comprehensive test suite.
Low code complexity.

More details about LightDM's design can be found here.

Installation

Tip: Stable releases are even-numbered (1.8, 1.10) while development releases are odd-numbered (1.9, 1.11). These development releases are available with lightdm-devel^AUR. Also available is lightdm-git^AUR.

Greeter

You will probably want to install a greeter. A greeter is a GUI that prompts the user for credentials, lets the user select a session, and so on. It is possible to use LightDM without a greeter, but only if an automatic login is configured; otherwise you will need to install xorg-server and one of the greeter packages below.

The official repositories contain the following greeters:

lightdm-gtk-greeter: This is the default greeter LightDM attempts to use, unless configured otherwise.
lightdm-deepin-greeter (deepin-session-shell): A greeter from the Deepin project.
lightdm-pantheon-greeter: A greeter from the elementary OS project.
lightdm-slick-greeter: A GTK based greeter focused more on appearance than lightdm-gtk-greeter, forked from lightdm-unity-greeter^AUR, and default in Linux Mint.
lightdm-webkit2-greeter: A greeter that uses Webkit2 for theming. It supersedes lightdm-webkit-greeter^AUR.
lightdm-webkit-theme-litarvan: A modern and full-featured Webkit2 LightDM theme.

Other alternative greeters are available in the AUR:

lightdm-unity-greeter^AUR: The greeter used by Unity.
lightdm-mini-greeter^AUR: A minimal, configurable, single-user greeter.
lightdm-webkit-theme-aether^AUR: A sleek, straightforward Arch Linux themed login screen written on lightdm and the lightdm-webkit2-greeter.
lightdm-elephant-greeter-git^AUR: A small and simple greeter that runs in the cage Wayland compositor per default.

You can set the default greeter by changing the [Seat:*] section of the LightDM configuration file, like so:

/etc/lightdm/lightdm.conf

[Seat:*]
...
greeter-session=lightdm-yourgreeter-greeter
...

One way to check which greeters are available is to list the files in the /usr/share/xgreeters directory; each .desktop file represents an available greeter. In this example, the lightdm-gtk-greeter and lightdm-webkit2-greeter greeters are available:

$ ls -1 /usr/share/xgreeters/
lightdm-gtk-greeter.desktop
lightdm-webkit2-greeter.desktop

Enabling LightDM

Make sure to enable lightdm.service so LightDM will be started at boot; see also Display manager#Loading the display manager.

Command line tool

LightDM offers a command line tool, dm-tool, which can be used to lock the current seat, switch sessions, etc, which is useful with 'minimalist' window managers and for testing. To see a list of available commands, execute:

$ dm-tool --help

User switching

The factual accuracy of this article or section is disputed.

Reason: Is this warning inappropriate? dm-tool lock and dm-tool switch-to-greeter are NOT screen lockers. They only switch to the LightDM greeter and send a notification to lock the session (as loginctl lock-session). This notification should be processed by a screen locker or redirected by xss-lock. In the absence of a screen locker to listen, there is nothing dm-tool ... can do - but that's not LightDM's fault. This issue is well known and touched upon here and here. (Discuss in Talk:LightDM)

Warning: The use of lightDM's built-in screen lockers like dm-tool lock or dm-tool switch-to-greeter are not recommended. Use light-locker or something from List of applications/Security#Screen lockers.

LightDM's dm-tool command can be used to allow multiple users to be logged in on separate ttys. The following will send a signal requesting that the current session be locked and then will initiate a switch to LightDM's greeter, allowing a new user to log in to the system.

$ dm-tool switch-to-greeter

Testing

First, install xorg-server-xephyr from the official repositories.

Then, run LightDM as an X application:

$ lightdm --test-mode --debug

Optional configuration and tweaks

LightDM can be configured by modifying its configuration file, /etc/lightdm/lightdm.conf.

Some greeters have their own configuration files. For example:

lightdm-gtk-greeter: /etc/lightdm/lightdm-gtk-greeter.conf (or you can use the lightdm-gtk-greeter-settings gui).

lightdm-webkit2-greeter: /etc/lightdm/lightdm-webkit2-greeter.conf

X session wrapper

This article or section is a candidate for merging with Xprofile.

Notes: Duplicated information (Discuss in Talk:LightDM)

If you are migrating from xinit, you will notice that the display is not launched by your shell. This is because, as opposed to your shell starting the display (and the display inheriting the environment of your shell), LightDM starts your display and does not source your shell. LightDM launches the display by running a wrapper script and that finally exec's your graphic environment. By default, /etc/lightdm/Xsession is run.

Environment variables

The script checks and sources /etc/profile, ~/.profile, /etc/xprofile and ~/.xprofile, in that order. If you are using a shell that does not source any of these files, you can create an ~/.xprofile to do so. (In this example, the login shell is zsh)

~/.xprofile

#!/bin/sh
[ -f ~/.config/zsh/.zshenv ] && . ~/.config/zsh/.zshenv

If you have shell variables that are important for your display (such as Gtk or QT themes, GNUPG location, configuration overrides, etc.) this will let your graphic environment have access to your environment without having to be launched by your login shell.

Keymap

The script runs Xkbmap with arguments provided in files /etc/X11/Xkbmap, ~/.Xkbmap. If those files are not found, it runs xmodmap with /etc/X11/Xmodmap, ~/.Xmodmap. If using xkbmap, the files are parsed using cat. The following example works

~/.Xmodmap

-model pc105 -layout us,us,tr -variant ,dvorak,f -option grp:caps_toggle

Otherwise, the session inherits the system default mapping of X11. This mapping can be defined in the xorg configuration files, either manually or with localectl set-x11-keymap. See Xorg/Keyboard configuration#Setting keyboard layout.

Multiple keyboard layouts in lightdm-gtk-greeter

To enable users switch between pre-defined keyboard layouts on the log-in screen enable the drop-down menu and configure the layouts. Either use the lightdm-gtk-greeter-settings gui or edit the configuration file directly:

/etc/lightdm/lightdm-gtk-greeter.conf

[greeter]
indicators = ~hosts;~spacer;~clock;~spacer;~layout;~language;~session;~ally;~power

Use localectl to set multiple layouts, e.g. de and its “variant” neo with the latter as primary:

# localectl --no-convert set-x11-keymap de,de pc105 neo,

Note the trailing comma which implies a blank variant for the second de.

Changing background images/colors

You can set the background to a hex color or an image. Some greeters offer more robust background options like background selection from the login screen, random backgrounds, etc.

GTK greeter

You can use the lightdm-gtk-greeter-settings gui.

Users wishing to customize the wallpaper on the greeter screen need to edit /etc/lightdm/lightdm-gtk-greeter.conf and define the background variable under the [greeter] section. For example:

/etc/lightdm/lightdm-gtk-greeter.conf

[greeter]
background=/usr/share/pixmaps/black_and_white_photography-wallpaper-1920x1080.jpg

Note: It is recommended to place the PNG or JPG file in /usr/share/pixmaps since the LightDM user needs read access to the wallpaper file.

GTK3 themes can be specified with the theme-name variable in the [greeter] section. The icon and cursor theme can be set in the same way, as shown in the following example:

/etc/lightdm/lightdm-gtk-greeter.conf

[greeter]
theme-name = Tela
icon-theme-name = Tela
cursor-theme-name = Tela
cursor-theme-size = 32
font-name = Cantarell 20

Webkit2 greeter

The lightdm-webkit2-greeter allows you to choose a background image directly on the login screen. It also offers an option to display a random image each time it starts if you use the Material theme. By default, images are sourced from /usr/share/backgrounds. You can change the background images directory by editing lightdm-webkit2-greeter.conf. For example:

/etc/lightdm/lightdm-webkit2-greeter.conf

[branding]
background_images = /usr/share/backgrounds

Note: The background images directory must be accessible to the LightDM user so it should not be located anywhere under /home.

Unity greeter

Users using the lightdm-unity-greeter^AUR must edit the /usr/share/glib-2.0/schemas/com.canonical.unity-greeter.gschema.xml file and then execute:

# glib-compile-schemas /usr/share/glib-2.0/schemas/

According to this page.

Slick Greeter

Use the lightdm-settings^AUR GUI

Changing your avatar

First, make sure the accountsservice package from the official repositories is installed, then set it up as follows, replacing username with the desired user's login name.

Create the file /var/lib/AccountsService/icons/username.png using a 96x96 PNG image file. Different image file formats are possible too, e.g., JPEG.
Alternatively, create the image file as /home/username/.face and skip the next step if the defaults already point to the user home directory path
Edit or create the account settings file /var/lib/AccountsService/users/username, and add the lines

[User]
Icon=/var/lib/AccountsService/icons/username.png

The filename here should point to the icon created in the first step, so adjust the filename extension if necessary.

Note: Make sure that both created files have 644 permissions, use chmod to correct them.

Sources of Arch-centric 64x64 icons

The archlinux-artwork^AUR package contains some nice examples that install to /usr/share/archlinux/icons and that can be copied to /usr/share/icons/hicolor/64x64/devices as follows:

# find /usr/share/archlinux/icons -name "*64*" -exec cp {} /usr/share/icons/hicolor/64x64/devices \;

After copying, the archlinux-artwork^AUR package can be removed.

Enabling autologin

Edit the LightDM configuration file and ensure these lines are uncommented and correctly configured:

/etc/lightdm/lightdm.conf

[Seat:*]
autologin-user=username

You must be part of the autologin group to be able to login automatically without entering your password:

# groupadd -r autologin
# gpasswd -a username autologin

LightDM logs in using the session specified in the ~/.dmrc of the user getting logged in automatically. To override this file, specify autologin-session in lightdm.conf:

/etc/lightdm/lightdm.conf

[Seat:*]
autologin-user=username
autologin-session=session

The list of valid session names can be found by listing /usr/share/xsessions/*.desktop for X's sessions and /usr/share/wayland-sessions/*.desktop for Wayland's.

Note: GNOME users, and by extension any gnome-keyring user will have to set up a blank password to their keyring for it to be unlocked automatically.

Enabling interactive passwordless login

LightDM goes through PAM so you must configure the lightdm configuration of PAM:

/etc/pam.d/lightdm

#%PAM-1.0
auth        sufficient  pam_succeed_if.so user ingroup nopasswdlogin
auth        include     system-login
...

You must then also be part of the nopasswdlogin group to be able to login interactively without entering your password:

# groupadd -r nopasswdlogin
# gpasswd -a username nopasswdlogin

Note: GNOME users, and by extension any gnome-keyring user may have to follow the instructions at the end of the previous section on enabling autologin.

To create a new user account that logs in automatically and additionally able to login again without a password the user can be created with supplementary membership of both groups, e.g.:

# useradd -mG autologin,nopasswdlogin -s /bin/bash username

Enabling guest sessions

Note: A guest user has passwordless access to your system after enabling this feature.

To enable guest sessions in LightDM (without changing your system configuration) you need at least two things:

a guest-account-script: defaults to guest-account and accepts two commands:
- add (to create a temporary guest system account and returns the user name of the created account)
- remove account name(to delete the corresponding account)
an autologin group to which the created guest account must be added (cf. /etc/pam.d/lightdm-autologin)

There are two AUR packages that enable guest sessions in lightdm:

lightdm-guest^AUR which provides the (largely unmodified) upstream guest-session script as well as lightdm itself.
lightdm-guest-account^AUR which provides only a minimal version of the script.

Hiding system and services users

To prevent system users from showing-up in the login, install the optional dependency accountsservice, or add the user names to /etc/lightdm/users.conf under hidden-users. The first option has the advantage of not needing to update the list when more users are added or removed.

Migrating from SLiM

This article or section is a candidate for merging with Display Manager.

Notes: Not LightDM specific (or even SLiM specific for that matter as XDM also uses xinitrc). Perhaps this merits a one-liner somewhere on the Display Manager page? (Discuss in Talk:LightDM)

Move the contents of xinitrc to xprofile, removing the call to start the window manager or desktop environment.

Login using ~/.xinitrc

See Display manager#Run ~/.xinitrc as a session.

NumLock on by default

Install the numlockx package and then edit /etc/lightdm/lightdm.conf:

/etc/lightdm/lightdm.conf

[Seat:*]
greeter-setup-script=/usr/bin/numlockx on

Default session

Lightdm, like other DMs, stores the last-selected xsession in ~/.dmrc. See Display manager#Session configuration for more info.

Adjusting the login window's position

GTK greeter

Users need to edit /etc/lightdm/lightdm-gtk-greeter.conf and enter a value for the position variable. It accepts x and y values, either absolute (in pixels) or relative (in percent). Each value can also have an additional anchor location for the window, start, center and end separated from the value by a comma.

Example:

position=200,start 50%,center

VNC Server

Lightdm can also be used to connect to via VNC. Make sure to install tigervnc on the server side and optionally as your VNC client on the client PC.

Setup an authentication password on the server as root:

# vncpasswd /etc/vncpasswd

Edit the LightDM configuration file as shown below. Note that listen-address configures the VNC to only listen to connections from localhost. This is used to only allow connections via SSH and port forwarding. On the SSH client, make sure that you use localhost:5900 for the tunnel destination; using 127.0.0.1:5900 or ::1:5900 is not reliable on dual stack network connections. If you want to allow insecure connections you can disable this setting.

/etc/lightdm/lightdm.conf

[VNCServer]
enabled=true
command=Xvnc -rfbauth /etc/vncpasswd
port=5900
listen-address=localhost
width=1024
height=768
depth=24

Now open an SSH tunnel and connect to localhost as described in TigerVNC#On the client.

Note: If you get a blank screen upon opening the VNC connection, try a different LightDM greeter.

Lock the screen using light-locker

light-locker is a simple screen locker using LightDM to authenticate the user. Once installed and running, you can lock your session via:

$ light-locker-command -l

This requires light-locker to be started at the beginning of your session. By default, this is enabled through XDG Autostart. See Autostarting for more options.

Multiple-monitor setup

Sometimes LightDM does not set the monitor resolution correctly on a multiple-monitor setup. The following Xorg configuration works with two monitors: a large primary screen on the left side, and a secondary smaller screen to its right. The order can be reversed and tweaked.

/etc/X11/xorg.conf.d/52-resolution-fix.conf

Section "Monitor"
    Identifier "DP1"
    Option "PreferredMode" "3840x2160"
    Option "Primary" "1"
EndSection
Section "Monitor"
    Identifier "eDP1"
    Option "PreferredMode" "1920x1080"
    Option "RightOf" "DP1"
EndSection

This makes the display-setup-script tweaks from /etc/lightdm/lightdm.conf redundant.

Troubleshooting

Autologin does not work

Ensure autologin-user= in /etc/lightdm/lightdm.conf contain the correct values. Trailing whitespace will cause errors.

If autologin fails with a blank screen or if the login screen immediately returns, you may need to set logind-check-graphical=true.

You can also install lightdm-autologin-greeter-git^AUR for this special purpose.

Viewing current configuration

To view effective configuration, run:

$ lightdm --show-config

This will show current settings, with the configuration files these settings were read from.

LightDM not starting and screen flashing

If you encounter consistent screen flashing and ultimately no LightDM on boot, ensure that you have defined the greeter correctly in LightDM's configuration file. And if you have correctly defined the GTK greeter, make sure the xsessions-directory (default: /usr/share/xsessions) exists and contains at least one .desktop file.

The same error can happen on lightdm startup if the last used session is not available anymore (eg. you last used gnome and then removed the gnome-session package): the easiest workaround is to temporarily restore the removed package. Another solution might be:

# dbus-send --system --type=method_call --print-reply --dest=org.freedesktop.Accounts /org/freedesktop/Accounts/User1000 org.freedesktop.Accounts.User.SetXSession string:xfce

This example sets the session "xfce" as default for the user 1000.

Wrong locale displayed

In case of your locale not being displayed correctly in Lightdm add your locale to /etc/environment:

LANG=pt_PT.utf8

Alternatively if you want LightDM and its greeters to be in a language other than your set system locale, you can use the Environment= option in Systemd#Drop-in files.

Unresponsive for a few minutes after startup

You may have to download more entropy. Install and enable haveged, c.f. https://github.com/canonical/lightdm/issues/17

Missing icons with GTK greeter

If you are using lightdm-gtk-greeter as a greeter and it shows placeholder images as icons, make sure valid icon themes and themes are installed and configured. Check the following file:

/etc/lightdm/lightdm-gtk-greeter.conf

[greeter]
theme-name=mate      # this should be the name of a directory under /usr/share/themes/
icon-theme-name=mate # this should be the name of a fully featured icons set directory under /usr/share/icons/

LightDM freezes on login attempt

You may find that after entering the correct username and password and attempting to log in, LightDM freezes and you are unable to continue to the desktop. To fix the issue, reinstall the gdk-pixbuf2 package. See this forum thread.

LightDM displaying in wrong monitor

If you are using multiple monitors, LightDM may display in the wrong one (e.g. if your primary monitor is on the right). To force the LightDM login screen to display on a specific monitor, edit /etc/lightdm/lightdm.conf and change the display-setup-script parameter like this:

/etc/lightdm/lightdm.conf

display-setup-script=xrandr --output HDMI-1 --primary

Replace HDMI-1 with your real monitor ID, which you can find from xrandr command output.

Alternatively, if you are using the GTK greeter, you can edit /etc/lightdm/lightdm-gtk-greeter.conf and add the active-monitor parameter like this:

/etc/lightdm/lightdm-gtk-greeter.conf

[greeter]
active-monitor=0

Replace 0 with the desired display number.

LightDM does not appear or monitor only displays TTY output

It may happen that your system boots so fast that LightDM service is started before your graphics drivers are properly loaded. If this is your case, you will want to add the following to your lightdm.conf file:

[LightDM]
logind-check-graphical=true

This setting will tell LightDM to wait until graphics devices are ready before spawning greeters/autostarting sessions on them.

LightDM is running with low FPS on Intel Graphics

See Intel graphics#AccelMethod.

Pulseaudio not starting automatically

See PulseAudio#Running.

Long pause before LightDM shows up when home is encrypted

Some LightDM themes try to access the user avatar located in HOME. If your HOME is encrypted, LightDM cannot access it and hangs. To prevent this from happening, you can either:

Set your avatar as explained in #Changing your avatar
for lightdm-gtk-greeter only: hide-user-image = true in /etc/lightdm/lightdm-gtk-greeter.conf

Boot hangs on "[ OK ] Reached target Graphical Interface."

There is a possibility that user and group lookups fail if you modified /etc/nsswitch.conf. That happens when:

nsswitch.conf group: includes ldap without setting nss_initgroups_ignoreusers ALLLOCAL in /etc/nslcd.conf

Wayland session not working with duplicate GNOME entries in greeter

Some greeters (lightdm-webkit2-greeter for example) do not support two sessions with the same name [1]. To check for duplicate entries:

$ ls -1 /usr/share/wayland-sessions /usr/share/xsessions

Rename the duplicate entry in /usr/share/xsessions. For example:

# mv /usr/share/xsessions/gnome.desktop /usr/share/xsessions/gnome.desktop.disabled

Login always segfaults on first attempt

Set a hostname as described in Network Page. See also FS#47694.

Infinite login loop

If you get stuck in loop in which you type your correct user and password but the screen goes black and the you are back in the login after every attempt, running rm ~/.Xauthority (or the stuck user's problematic .Xauthority) may fix the issue.

Another reason for this may be that you tried to recreate your "lightdm.conf" from scratch and your version is missing this line:

session-wrapper=/etc/lightdm/Xsession

In that case, lightdm tries to use "lightdm-session" as the session-wrapper which does not exist on Arch Linux.