Difference between revisions of "LightDM"

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Revision as of 23:16, 14 March 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 or lightdm-bzrAUR from the AUR.

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 either lightdm-gtk3-greeter or lightdm-gtk2-greeter. KDE users can install lightdm-kde-greeter, a greeter based on Qt.

Other greeters can be installed from the AUR as well:

You can change the default greeter at compile time by changing the line containing:

--with-greeter-session=lightdm-gtk-greeter

to

--with-greeter-session=lightdm-yourgreeter-greeter

Or, more easily, change the configuration file to state:

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

Optional Configuration and Tweaks

Some greeters have their own configuration files. For example, lightdm-gtk3-greeter and lightdm-gtk2-greeter have:

/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-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 the Icon

Users wishing to customize the icon on the greeter screen need to edit /etc/lightdm/lightdm-gtk-greeter.conf defining the logo variable.

Example:

logo=/usr/share/icons/hicolor/64x64/devices/archlinux-icon-crystal-64.svg

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
[SeatDefaults]
autologin-user=USERNAME
autologin-user-timeout=0
pam-service=lightdm-autologin

or execute:

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

PAM settings

Note: These steps may no longer be necessary.

LightDM goes through PAM even when autologin is enabled. You must make sure that PAM allows login without prompting for a password.

Create a new group called, say, autologin and add yourself to the group:

 groupadd autologin
 gpasswd -a username autologin

Edit /etc/pam.d/lightdm and locate the line "auth required pam_unix.so". Add new lines before and after it so that the section now reads:

 auth [success=1 default=ignore] pam_succeed_if.so user ingroup autologin
 auth required pam_unix.so
 auth optional pam_permit.so

This ensures that the user will not be asked for a password when logging in through LightDM's autologin. So any user you would like to login without typing password in LightDM just add to this group.

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 xfce4

With the release of Xfce4 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/bin/gdmflexiserver

Alternatively, see the XScreenSaver#Lightdm article.

See Also