"Failed to start session" after upgrade to 18.04

Question

After upgrading to 18.04 from 16.04 I get a login screen which looks complete but typing in my password gives the error failed to start session.

I can use Ctrl+Alt+F1 to access tty where logging in is successful but starting almost immediately terminates.

I have read similar solutions about installing ubuntu-session but attempting these gives unable to correct problems, you have held broken packages with the dependencies on gnome-shell and gnome-session-bin listed as unmet dependencies.

Solution

I took this along to a laptop clinic who solved the issue. The login screen, importantly, looked identical to the 16.04 Unity login screen which betrayed the problem in transferring to 18.04 (which has a very different looking login screen).

In TTY attempting to install certain packages gave unmet dependencies, and following the chain down gave the ligbm1 package at the base. This is the dependency for a lot of unity and xserver packages (attempting startx also failed). Uninstalling ligbm1 and then installing it again allowed installing ubuntu-desktop without error.

Comments

[m_krsic]

What happens if you try to run sudo apt-get install -f in tty?

[Nathan B]

Same problem here