LightDM

LightDM (Light Display Manager) is a light weight display manager and part of the Free Desktop project. LightDM is designed to be independent of the desktop environment in use just as the original XDM was.

Installation
Before starting you should have X properly running.

LightDM is currently masked and depends on accounts service which is also masked. If masked (change to your arch,  for example):

LightDM includes support for gtk (The GIMP Toolkit) and qt4 (Qt Toolkit) greeters, which one gets built is determined by your use flags.

Now install :

Configuration
Edit your or  to let it know to use LightDM as the display manager

Add xdm to the default run-level

LightDM Configuration
The configuration files are in /etc/lightdm/.

By default LightDM stores greeters in /usr/share/xgreeters.

By default LightDM only displays users with a UID >= 1000. This is configured in users.conf. You can also specify individual user names that you do not want to be displayed.

Selecting a Window Manager
Window Managers are stored in /usr/share/xsessions/. At login the user can select which window manager session to use.