I installed gnome-shell and selected gdm3 and after rebooting I wasn't able to login. It only shows the Ubuntu loading screen. I tried to change the displaymanager via root terminal in recovery mode with dpkg-reconfigure lightdm but it says I can't change it, because I'm in read only mode? super+alt+f1 also doesn't work, it says it's waiting for a process which never finishes.
I also used apt purge gnome-shell but that didn't help either. Also tried dpkg-reconfigure xserver-xorg and starting lightdm. That was everything I found here but didn't fix my problem. Any other suggestion?
2 Answers
I was able to fix it. The problem was that I wasn't able to change the displaymanager because the root shell in recovery mode is by default read only.
Type in
mount -o remount,rw /to mount the drive with write permissions.then
dpkg-reconfigure gdm3(or lightm) and switch back to lightdm
I also found that there is a bug with Ubuntu GNOME with the nvidia graphics drivers, which may have caused the problem in the first place. In the bug report it is suggested to install xserver-xorg-legacy. Hope that will help others.
First go to grub2 or Ubuntu recovery mode, by holding on tab or shift button while the Computer brand logo comes up (or Motherboard logo), after you reach the next screen, you will see advanced options, where you will find list of the kernels your OS has now. Select the recovery of the kernel you are using or just use the top kernel, mine was 4.4.0.71 (recovery).
After that select "Drop to root shell prompt with Networking" then at first press enter.
To reinstall reinstall Unity to make your system usable again type the following commands:
- mount -o rw,remount / (or mount --all)
- sudo apt install ubuntu-desktop unity
- sudo apt remove gnome-shell ubuntu-gnome-desktop and enter y
- sudo apt update && apt upgrade
- sudo reboot
I think this will help.
