I recently upgraded my laptop from Ubuntu 17.04 to 18.04. It worked perfectly well and I have been using it without any problem, but yesterday I issued
sudo apt upgrade and it upgraded some packages.
Then I restarted the PC and it didn't boot up again. After displaying the Ubuntu logo I get a screen like below and after flashing several times it freezes.
Note that the message on the bottom line is changing for each restart. I am able to start a
tty session there log into my account.
normal boot messages usually covered by splash screen
To my knowledge, the problem is
gdm3 (GNOME display manager) fails to start, since when I issue
sudo systemctl restart gdm3 the screen flashes several times and again stays in tty session.
Can anyone suggest a solution to this without complete reinstallation of the system?
I had a similar problem updating from 16.04 to 18.04.
The solution in my particular case was to deactivate Wayland modifying
/etc/gdm3/custom.confuncommenting or enabling
WaylandEnable=falseso the GNOME display manager will always load the GNOME desktop environment from gnome-desktop and not Wayland. This is because Wayland usually has errors with some graphics drivers.
This can be done easily from an Ubuntu live USB or if possible start in Recovery mode from the grub menu.