LightDM (Lightweight Display Manager) is a Display Manager for the X.org X server. It is the default X display manager of Ubuntu. LightDM starts an X session and presents the user with a graphical login screen, so the user does not have to issue commands such as `startx` to start the X server
LightDM is the default X display manager of Ubuntu. It starts the X server, user sessions and greeter (graphical login screen).
Key Features of LightDM:
- Cross-desktop - supports different desktop technologies.
- Supports different display technologies (X, Mir, ...).
- Lightweight - low memory usage and fast performance.
- Low code complexity
- Supports remote login (incoming - XDMCP, VNC, outgoing - XDMCP, pluggable).
- Easily themeable
- Support for 3D
- Offers guest sessions.
To understand more about LightDM and its role in the Ubuntu login process you may refer to this answer.
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