Lightdm: Display Manager For Linux

LightDM is a cross-desktop display manager. It provides a lightweight and customizable login screen for Linux systems. LightDM supports multiple desktop environments and uses separate greeter applications to render the user interface.

LightDM Installation

Install LightDM on Debian-based systems:

$ sudo apt install lightdm

Install LightDM on Arch-based systems:

$ sudo pacman -S lightdm

Install a greeter package. The GTK greeter is the most common choice:

$ sudo apt install lightdm-gtk-greeter

LightDM Configuration

The main configuration file is located at /etc/lightdm/lightdm.conf. Additional configuration files can be placed in /etc/lightdm/lightdm.conf.d/.

View Current LightDM Configuration

Display the effective configuration with source file locations:

$ lightdm --show-config

This command shows all active settings and identifies which configuration files define each option.

Change Default Display Manager

Switch to LightDM as the default display manager using dpkg-reconfigure:

$ sudo dpkg-reconfigure lightdm

Select LightDM from the list of available display managers.

Enable LightDM Service

Enable LightDM to start at boot. First disable any existing display manager:

$ sudo systemctl disable gdm

Enable the LightDM service:

$ sudo systemctl enable lightdm

Reboot the system to apply changes:

$ sudo systemctl reboot

LightDM Autologin Setup

Configure automatic login by editing /etc/lightdm/lightdm.conf or creating a file in /etc/lightdm/lightdm.conf.d/.

Add these lines under the [Seat:*] section:

[Seat:*]
autologin-user=username
autologin-user-timeout=0

Replace username with the account name for automatic login.

Enable LightDM User List

By default, LightDM requires users to type their username. Enable a clickable user list for easier selection.

Create the configuration file:

$ sudo nano /etc/lightdm/lightdm.conf.d/01_user-list.conf

Add this content:

[Seat:*]
greeter-hide-users=false

Restart LightDM to apply the change:

$ sudo systemctl restart lightdm

LightDM Greeter Configuration

Different greeters have their own configuration files. The GTK greeter uses /etc/lightdm/lightdm-gtk-greeter.conf.

Change Greeter Background

Edit the greeter configuration:

$ sudo nano /etc/lightdm/lightdm-gtk-greeter.conf

Set a custom background image:

[greeter]
background=/path/to/image.png

Use a solid color by specifying a hex value:

[greeter]
background=#2d2d2d

Change Default Session

Set the default desktop session in /etc/lightdm/lightdm.conf:

[Seat:*]
user-session=xfce

Available sessions are listed in /usr/share/xsessions/. List available sessions:

$ ls /usr/share/xsessions/

LightDM Test Mode

Test LightDM configuration without logging out. Install the Xephyr nested X server:

$ sudo apt install xserver-xephyr

Run LightDM in test mode:

$ lightdm --test-mode --debug

This opens LightDM in a window for testing greeter themes and configuration changes.

LightDM Greeters

Several greeter options are available for different desktop environments and visual preferences.

Greeter	Description
lightdm-gtk-greeter	Default GTK-based greeter with moderate resource usage
lightdm-slick-greeter	Appearance-focused GTK greeter from Linux Mint
lightdm-webkit2-greeter	HTML/CSS/JavaScript themeable greeter
lightdm-kde-greeter	KDE Plasma integrated greeter

Set the active greeter in /etc/lightdm/lightdm.conf:

[Seat:*]
greeter-session=lightdm-slick-greeter

LightDM Troubleshooting

Check LightDM service status:

$ systemctl status lightdm

View LightDM logs for errors:

$ cat /var/log/lightdm/lightdm.log

View greeter-specific logs:

$ cat /var/log/lightdm/seat0-greeter.log