# The Light Display Manager (LightDM)

## Description

*LightDM* is a cross-desktop display manager.
A display manager is a daemon that:

* Runs display servers (e.g. X) where necessary.
* Runs greeters to allow users to pick which user account and session type to use.
* Allows greeters to perform authentication using PAM.
* Runs session processes once authentication is complete.
* Provides remote graphical login options.

Key features of LightDM are: 

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

## Installation

LightDM is available in the following distributions:

* [[Arch|https://www.archlinux.org/packages/?name=lightdm]]
* [[Debian|http://packages.qa.debian.org/l/lightdm.html]]
* Elementary OS
* [[Fedora|https://apps.fedoraproject.org/packages/lightdm]]
* [[Gentoo|http://packages.gentoo.org/package/x11-misc/lightdm]]
* [[Mageia|http://mageia.madb.org/package/show/name/lightdm/application]]
* [[OpenSUSE|http://software.opensuse.org/package/lightdm]]
* [[Ubuntu|https://launchpad.net/ubuntu/+source/lightdm]]

Development is hosted on [[Launchpad|https://launchpad.net/lightdm]].
[[Tarball releases|https://launchpad.net/lightdm/+download]] are available.

Releases are synchronised with the [[Ubuntu release schedule|https://wiki.ubuntu.com/Releases]] and supported for the duration of each Ubuntu release. Each release is announced on the [[mailing list|http://lists.freedesktop.org/mailman/listinfo/lightdm]].

The core LightDM project does not provide any greeter with it and you should install a greeter appropriate to your system.
Popular greeter projects are:

* [[LightDM GTK+ Greeter|https://launchpad.net/lightdm-gtk-greeter]] - a greeter that has moderate requirements (GTK+).
* [[LightDM KDE|http://projects.kde.org/lightdm]] - greeter used in [[KDE||http://kde.org]] (Qt)
* [[LXqt Greeter|https://github.com/lxde/lxqt-lightdm-greeter]] - greeter used in [[LXqt|http://lxqt.org]] (Qt)
* [[Pantheon Greeter|https://launchpad.net/pantheon-greeter]] - greeter used in [[Elementary OS|http://elementaryos.org]] (GTK+/Clutter).
* [[Unity Greeter|https://launchpad.net/unity-greeter]] - greeter used in [[Unity|https://launchpad.net/unity]].
* Run with no greeter (automatic login only)
* [[Write your own|Software/LightDM/Development]]...

## Configuration

LightDM configuration is provided by the following files:

    /usr/share/lightdm/lightdm.conf.d/*.conf
    /etc/lightdm/lightdm.conf.d/*.conf
    /etc/lightdm/lightdm.conf

System provided configuration should be stored in */usr/share/lightdm/lightdm.conf.d/*.
System administrators can override this configuration by adding files to  */etc/lightdm/lightdm.conf.d/* and */etc/lightdm/lightdm.conf*.
Files are read in the above order and combined together to make the LightDM configuration.

For example, if a sysadmind wanted to override the system configured default session (provided in */usr/share/lightdm/lightdm.conf.d*) they should make a file */etc/lightdm/lightdm.conf.d/50-myconfig.conf* with the following:

    [SeatDefaults]
    user-session=mysession

Configuration is in keyfile format.
For most installations you will want to change the keys in the [SeatDefaults] section as this applies to all seats on the system (normally just one).
A configuration file showing all the possible keys is provided in [[data/lightdm.conf|http://bazaar.launchpad.net/~lightdm-team/lightdm/trunk/view/head:/data/lightdm.conf]].

See [[Common Configuration|CommonConfiguration]] for common configuration options.

## Questions

Questions should be asked on the [[mailing list|http://lists.freedesktop.org/mailman/listinfo/lightdm]].
All questions are welcome.

[[Stack Overflow|http://stackoverflow.com/search?q=lightdm]] and [[Ask Ubuntu|http://askubuntu.com/search?q=lightdm]] are good sites for frequently asked questions.

## Development

See [[Development]].