# LightDM

Related articles

- Display manager
- GDM
- KDM
- LXDM

LightDM is a cross-desktop display manager that aims to be the standard display manager for the X server. Its key features are:

- A lightweight codebase
- Standards compliant (PAM, logind, etc)
- A well defined interface between the server and the user interface.
- Cross-desktop (user interfaces can be written in any toolkit).

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

## Installation

Install lightdm. Note that 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-develAUR. Also available is lightdm-bzrAUR.

### Greeter

You will also need to install a greeter (a user interface for LightDM). The reference greeter is lightdm-gtk-greeter. KDE users can install lightdm-kde-greeter, a greeter based on Qt.

Other greeters can be installed from the AUR as well:

- lightdm-another-gtk-greeterAUR: A GTK3 greeter with custom theme support
- lightdm-webkit-greeterAUR: A greeter that uses Webkit for theming.
- lightdm-crowd-greeterAUR: A 3D greeter that lets you select your profile from 3D characters walking around.
- lightdm-unity-greeterAUR: The greeter used by Ubuntu's Unity.
- lightdm-razor-greeterAUR[broken link: package not found]: A greeter for the Razor-qt desktop environment.
- lightdm-pantheon-greeterAUR: A greeter from the elementary OS project.

You can change the default greeter by changing the configuration file under the `[SeatDefaults]` section, to state:

    /etc/lightdm/lightdm.conf

    [SeatDefaults]
    ...
    greeter-session=lightdm-yourgreeter-greeter

## Enabling LightDM

Make sure to enable `lightdm.service` so LightDM will be started at boot.

## 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

## 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

Some greeters have their own configuration files. For example, lightdm-gtk-greeter has:

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

and lightdm-kde-greeter has:

    /etc/lightdm/lightdm-kde-greeter.conf

as well as a section in KDE's System Settings (recommended).

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

### Changing background images/colors

Users wishing to have a flat color (no image) may simply set the `background` variable to a hex color.

Example:

    background=#000000

If you want to use an image instead, see below.

#### GTK+ greeter

Users wishing to customize the wallpaper on the greeter screen need to edit `/etc/lightdm/lightdm-gtk-greeter.conf` defining the `background` variable.

Example:

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

#### Unity greeter

Users using the lightdm-unity-greeterAUR 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.

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.

#### KDE greeter

Go to System Settings > Login Screen (LightDM) and change the background image for your theme.

### Changing your avatar

#### The .face way

Users wishing to customize their image on the greeter screen need to place an PNG image called `.face` or `.face.icon` in their home directory. Make sure it can be read by LightDM.

Note: As of December 2013, some people have issues where the icon file does not get picked up. The preferred way is to install accountsservice and use the following AccountsService way.

#### The AccountsService way

The .face way is known to cause issues, fortunately LightDM is able to use AccountsService automatically. 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. The use of the .png file extension is presumably optional. If you are using KDE, you can also change your picture via the KDE System Settings.

- Edit or create the file `/var/lib/AccountsService/users/username`, and add the lines

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

- Create the file `/var/lib/AccountsService/icons/username.png` using a 96x96 PNG icon file.

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

### Sources of Arch-centric 64x64 icons

The archlinux-artworkAUR package from the AUR 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-artworkAUR package can be removed.

### Enabling autologin

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

    /etc/lightdm/lightdm.conf

    [SeatDefaults]
    pam-service=lightdm
    pam-autologin-service=lightdm-autologin
    autologin-user=username
    autologin-user-timeout=0
    session-wrapper=/etc/lightdm/Xsession

LightDM goes through PAM even when `autologin` is enabled. 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

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

### 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

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

### NumLock on by default

Install the numlockx package and the edit `/etc/lightdm/lightdm.conf` adding the following line:

    greeter-setup-script=/usr/bin/numlockx on

### User switching under Xfce4

If you use the Xfce desktop, the Switch User functionality of the Action Button found in your Application Launcher specifically looks for the gdmflexiserver executable in order to enable itself. If you provide it with an executable shell script `/usr/bin/gdmflexiserver` consisting of

    #!/bin/sh
    /usr/bin/dm-tool switch-to-greeter

then user switching in Xfce should work with Lightdm.

Alternatively, if you use the Whisker Menu, you can go to Properties -> Commands and change the "Switch Users" command directly to:

     dm-tool switch-to-greeter

You can also switch users from the XScreenSaver lock screen - see XScreenSaver#Lightdm.

### Default session

Lightdm, like other DMs, stores the last-selected xsession in `~/.dmrc`. See Display manager#Session list 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

## Troubleshooting

If you encounter consistent screen flashing and ultimately no lightdm on boot, ensure that you have defined the greeter correctly in lightdm's config 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

### Xresources not being parsed correctly

LightDM has an upstream bug where your Xresources file will not be loaded with a pre-processor. In practical terms, this means that variables set with `#define` are not expanded when called later. You may see this reflected as an all-pink screen if using a custom color set with urxvt. To fix it, edit `/etc/lightdm/Xsession` and search for the line:

    xrdb -nocpp -merge "$file"

Change it to read:

    xrdb -merge "$file"

Your Xresources will now be pre-processed so that variables are correctly expanded.

### Missing icons with GTK greeter

If you're 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/

### White screen after upgrading the GTK greeter to 2.0.0

The 2.0.0 greeter may display only a white screen with specific configurations. Clicking the white screen may get rid of it. A fix is pending for the next release, in the meantime you can set `active-monitor=0` (or the appropriate number) in `/etc/lightdm/lightdm-gtk-greeter.conf`.

See FS#43999 for reference.

### 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 HDMI1 --primary

Replace HDMI1 with your real monitor ID, which you can find from xrandr command output.

### Pulseaudio not starting automatically

See PulseAudio#Running.

## See also

- light-locker, a screen locker using LightDM.
- Ubuntu Wiki article
- Gentoo Wiki article
- Launchpad Page
- LightDM blog

Category:

- Display managers