LightDM

LightDM is a cross-desktop display manager whose aim is to be the standard display manager for the X server.

The key features (as listed by upstream) include:

• A well-defined greeter API allowing multiple GUIs.
• Support for all display manager use cases, with plugins where appropriate.
• Low code complexity.
• Fast performance.

Installation

USE flags

Emerge

Install x11-misc/lightdm :

Configuration

The (global) configuration file for LightDM can be found at /etc/lightdm/lightdm.conf. Upon successful authentication, LightDM starts an Xsession through the following configuration option (enabled by default):

[Seat:*]
...
session-wrapper=/etc/lightdm/Xsession
...

GTK

The greeter allows to select logging into one of the installed type of sessions through the icon in the Panel on top of the display. This makes it unnecessary to configure the session startup through user profile configurations. For example, xfce-base/xfce4-session installs /usr/share/xsessions/xfce.desktop which enables the greeter to offer the Xfce session. The default is an Xsession which relies on user profile files.

The GTK greeter configuration can be modified by manually editing the following file:

/etc/lightdm/lightdm-gtk-greeter.conf

Qt

Currently Gentoo does not support the Qt greeter since it was moved out into it's own project at https://github.com/surlykke/qt-lightdm-greeter however USE flag support is in the x11-misc/lightdm package if someone wanted to add the greeter support.

Boot service

OpenRC

With display-manager

Set LightDM as the default display manager:

DISPLAYMANAGER="lightdm"

To start LightDM on boot, add dbus and display-manager to the default runlevel. dbus is necessary because LightDM depends on it to pass messages:

To start LightDM now:

With the deprecated xdm init script

Set LightDM as the default display manager:

DISPLAYMANAGER="lightdm"

To start LightDM on boot, add dbus and xdm to the default runlevel. dbus is necessary because LightDM depends on it to pass messages:

To start LightDM now:

systemd

To start LightDM on boot:

To start LightDM now:

Command-line tool

LightDM includes a command-line tool, dm-tool, which can be used to switch user sessions, lock the current seat, etc. To see a list of available commands, use the --help option:

For example, to lock the current seat:

Tips

Running commands at log-in

A user can run some programs automatically when logging in using LightDM by adding commands in ~/.xprofile, which will be sourced by LightDM. For example:

# Starting redshift, setting the dpi with xrandr and set the brightness to 50% with xbacklight
xrandr--dpi192&
redshift-gtk&
xbacklight-set50&

Unlock GNOME Keyring

To unlock your GNOME Keyring (gnome-base/gnome-keyring ) automatically on login, edit /etc/pam.d/lightdm to look as follows. Note: Lines ending with the comment #keyring should be added.

auth substack system-local-login
auth optional pam_gnome_keyring.so #keyring
account substack system-local-login
password substack system-local-login
session substack system-local-login
session optional pam_gnome_keyring.so auto_start #keyring

Locking the screen with elogind after suspend or sleep

For security, it is good practice to lock the screen after elogind triggers suspend or sleep. This can be done easily by doing the following:

Install light-locker:

Start light-locker after the X server has started by putting light-locker & into either an ~/.xprofile or ~/.xinitrc file.

# Starting light-lock with X session
light-locker&

Create a lock.sh file under /lib64/elogind/system-sleep/ (be sure to add execute permissions to the file):

Troubleshooting

LightDM crashes upon first login if hostname changes during login

In some cases LightDM may crash when trying to log in for the first time if the hostname changes in the time between the boot and login (launchpad bug #1677058).

This may be encountered if net-misc/networkmanager is using the default settings to obtain the hostname from DHCP server and the hostname differs from the default one set on boot.

To disable NetworkManager hostname setting behavior, set the following line in [main] section of /etc/NetworkManager/NetworkManager.conf:

[main]
...
hostname-mode=none
...

LightDM fails to launch with Nvidia GPU

Users with Nvidia GPUs may encounter failures when using LightDM (GitHub issue #263).

A workaround for this issue involves editing /etc/lightdm/lightdm.conf and adding the line logind-check-graphical=false within the [LightDM] section.

[LightDM]
...
logind-check-graphical=false
...

See also

• SDDM — a modern display manager that supports both the X server and the Wayland protocol.

• Display manager