On a fresh Ubuntu 20.04 installation, I installed Unity and configured it to use lightdm in the installation wizard. The login screen looks different, where we now have the option to select the desktop environment to use before logging in.

sudo apt install ubuntu-unity-desktop

enter image description here

I then decided to switch back to the default GNOME desktop by uninstalling Unity. However, the login screen does not go back to the original one that came with the fresh Ubuntu 20.04 installation even after restarting the computer.

sudo apt purge unity-session unity
sudo apt autoremove
sudo apt install ubuntu-session gdm3

How can we restore the original login screen in Ubuntu 20.04?

  • sudo dpkg-reconfigure gdm3 whats happening?
    – PRATAP
    Sep 8, 2020 at 16:12
  • 1
    @UnKNOWn Thanks, sudo dpkg-reconfigure lightdm then selecting gdm3 fixed it. Sep 8, 2020 at 19:29

1 Answer 1


You missed one single step, and that is to reconfigure the system to use GDM again for login. This is done with the command

sudo dpkg-reconfigure lightdm

where lightdm is the login manager you currently use. As you also have GDM (package gdm3) installed, this command will show a prompt that lets you change the login manager in use.

  • Thanks. I had to do sudo dpkg-reconfigure lightdm instead, then select gdm3 when prompted. sudo dpkg-reconfigure gdm3 gives the error gdm.service is not active, cannot reload. invoke-rc.d: initscript gdm3, action "reload" failed. Sep 8, 2020 at 19:27
  • Thanks for the input. I will correct my answer.
    – vanadium
    Sep 9, 2020 at 6:15

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