Difference between revisions of "LightDM"

Revision as of 15:08, 20 August 2013

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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, ConsoleKit, 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 from the official repositories. You can also install lightdm-devel^AUR for the development branch or lightdm-bzr^AUR from the AUR.

If you want to be able to power off or restart your computer from LightDM, also install polkit.

Greeter

You will also need to install a greeter (a user interface for LightDM). The reference greeter is lightdm-gtk-greeter, which is provided by lightdm-gtk3-greeter. KDE users can install lightdm-kde-greeter, a greeter based on Qt.

Other greeters can be installed from the AUR as well:

• lightdm-webkit-greeter^AUR: A greeter that uses Webkit for theming.
• lightdm-crowd-greeter^AUR: A 3D greeter that lets you select your profile from 3D characters walking around.
• lightdm-unity-greeter^AUR: The greeter used by Ubuntu's Unity.
• razor-lightdm-greeter^AUR: A greeter for the Razor-qt desktop environment.
• lightdm-pantheon-greeter^AUR: A LightDM greeter from the ElementaryOS Project.

You can change the default greeter by changing the configuration file to state:

/etc/lightdm/lightdm.conf

greeter-session=lightdm-yourgreeter-greeter

Enabling LightDM

Make sure that the lightdm daemon is started at boot.

Testing

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

Then, run LightDM as an X application:

$ lightdm --test-mode --debug

Enabling power menu (restart, poweroff etc.)

By default, lightdm.service does not register itself as systemd-logind session, so all items in the power menu (restart, poweroff etc.) are hidden. A possible workaround is to create this polkit rule (also make sure polkit is installed):

/etc/polkit-1/rules.d/10-lightdm.rules

polkit.addRule(function(action, subject) {
    if(action.id.match("org.freedesktop.login1.") && subject.isInGroup("lightdm")) {
        return polkit.Result.YES;
    }
});

For more information:

• systemd#Power management
• xbmc#Enabling shutdown, restart, hibernate and suspend
• http://www.freedesktop.org/wiki/Software/systemd/logind/

Optional Configuration and Tweaks

Some greeters have their own configuration files. For example, lightdm-gtk3-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 directly modifying its configuration script or by using the lightdm-set-defaults applications that can be found in /usr/lib/lightdm/lightdm/. To see some of the options available, execute:

$ man lightdm-set-defaults

There are, however, a lot more variables to modify in the configuration file than by using the lightdm-set-defaults application.

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-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.

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 image called .face or .face.icon in their home directory. Make sure it can be read by LightDM.

The AccountsService way

The .face way is known to cause issues, fortunately LightDM is able to automatically use AccountsService if it is installed. AccountsService files need to be set up as follows:

• A user file named after your user in /var/lib/AccountsService/users/johndoe containing:

[User]
Icon=/var/lib/AccountsService/icons/johndoe

• A 96x96 PNG icon file in /var/lib/AccountsService/icons/johndoe

Sources of Arch-centric 64x64 Icons

The archlinux-artwork package from the official repositories 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 package can be removed.

Enabling Autologin

Edit the LightDM configuration file and change these lines to:

/etc/lightdm/lightdm.conf

autologin-user=<your_username>
autologin-user-timeout=0

or execute:

# /usr/lib/lightdm/lightdm/lightdm-set-defaults --autologin=USERNAME

LightDM goes through PAM even when autologin is enabled. You must be part of the autologin group to be able to login without entering your password:

# groupadd autologin
# gpasswd -a username autologin

Migrating from SLiM

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

NumLock ON

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 Xfce 4

With the release of Xfce 4.10, user switching is supported natively. To use it with LightDM, users need only to create a symlink:

# ln -s /usr/lib/lightdm/lightdm/gdmflexiserver /usr/local/bin/gdmflexiserver

Alternatively, see the XScreenSaver#Lightdm article.

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/xessions) exists and contains at least one .desktop file.

See Also

• Ubuntu Wiki article
• Gentoo Wiki article
• Launchpad Page
• LightDM blog