Switch Display Manager in Ubuntu 20.04

Once the boot process gets completed, we get a prompt to enter user and password to login. The type of login manager would depend on our Ubuntu configuration. If we intend to use CLI (Command-line interface), then we would get a default shell to login. Or else, a Display Manager in case of GUI (Graphical User Interface). In this article, we would focus on how to switch between different Display Manager in Ubuntu 20.04 release.

Although there are numerous Display Manager (both GUI and CLI) available, but we would focus on three prominent ones – GDM, LightDM and SDDM. In Ubuntu, GDM has been the default Display Manager in Ubuntu 16.10 and later. Many Ubuntu flavors still prefer to choose LightDM as default display manager.

Note: Following operations would require you to have superuser privileges. In case you don’t have one, then contact your System Administrator for assistance.

First, we will discuss how to install each Display Manager mentioned above.

Install GDM in Ubuntu

To install GDM (GNOME Display Manager), open a terminal and issue the following –

sudo apt install gdm3
Install LightDM in Ubuntu

To install LightDM, open a terminal and issue the following –

sudo apt install lightdm
Install SDDM in Ubuntu

To install SDDM (Simple Desktop Display Manager), open a terminal and issue the following –

sudo apt install sddm
Switch Display Manager in Ubuntu 20.04

Its not necessary to install all of the above mentioned Display Manager. Any two will suffice. First, we need to identify our default display manager. Therefore, issue the following in terminal –

cat /etc/X11/default-display-manager

This would return

for GDM3

/usr/sbin/gdm3

for LightDM

/usr/sbin/lightdm

and SDDM

/usr/sbin/sddm

Or, you can simply issue to get the status of active Display Manager –

systemctl status display-manager

Now, to switch between them – run the following command with active (or default) Display Manager –

sudo dpkg-reconfigure <Default_Display_Manager>

for instance (opt any one of three as per your System’s configuration),

sudo dpkg-reconfigure gdm3
sudo dpkg-reconfigure lightdm
sudo dpkg-reconfigure sddm

And, press OK. Next, you will be asked to select your default Display Manager (gdm3, lightdm or sddm).

On running – sudo dpkg-reconfigure gdm3, you may get following error –

gdm.service is not active, cannot reload.
invoke-rc.d: initscript gdm3, action "reload" failed.

In our case, we just needed to reboot our System. And, everything worked as it should.

In conclusion, we have discussed how to switch Display Manager in Ubuntu 20.04 release.