How To Change The Default Display Manager (Switch To GDM, LightDM, SDDM, Or LXDM) In Debian, Ubuntu Or Linux Mint

When installing a display manager on a Debian-based Linux distribution, you're asked which display manager should be used by default, but it may not be clear for some users how to change the display manager later on.

GDM3 (Gnome Display Manager) in Ubuntu 18.10

A display manager, or login manager, is a program that manages graphical display servers and handles user logins. This article explains how to change the display manager, from / to GDM (GDM and GDM3), LightDM, SDDM or LXDM. The instructions below should work on any Debian and Ubuntu based Linux distribution, including Linux Mint, elementary OS, and so on.

This can be useful in case you're having issues with your current display manager and you want to use a different one, in case you installed a desktop environment that uses a different display manager by default and you want to switch to it, and so on.


To change the default display manager on Debian, Ubuntu, Linux Mint, elementary OS and any Debian or Ubuntu-based Linux distribution we'll use dpkg-reconfigure, a tool provided by debconf, which can be used to reconfigure an already installed package by asking the configuration questions, much like when the package was first installed.

So to change the default display manager, use this command:

sudo dpkg-reconfigure some_installed_display_manager

In this command, replace some_installed_display_manager with one of the display managers installed on your system, for example gdm3, lightdm, sddm, lxdm, etc.. After running this command, it will list all installed display managers, allowing you to select the one to be used. If only one display manager is installed, this command won't work.

After selecting a new default display manager, reboot your system.

For example, if you have both LightDM and GDM3 installed on your system, the command to switch to either GDM3 or LightDM can be both:

sudo dpkg-reconfigure gdm3

and:

sudo dpkg-reconfigure lightdm

Any of these two commands work if you want to switch to either LightDM or GDM3, since both are installed in this example.

For the old GDM (used a while back - pre Ubuntu 16.04 for example), use gdm instead of gdm3 in the command.

In the same way, if you have SDDM or LXDM installed, you can use this command to change the display manager:

sudo dpkg-reconfigure sddm

or

sudo dpkg-reconfigure lxdm

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