Failed to start Light Display Manager on boot for Ubuntu 20
tl;dr; Light Service DM is not starting. I have tried fixing it via GDM3, was unable to do so due to broken packages. I think that somehow NVIDIA is involved, but I am not sure. Where to start from here?
Hi,
this afternoon I updated some packages. Tried to install gnome-control-center, since my Settings app was missing. Still was unable to install gnome-control-center, so I tried a reboot.. but then my screen got stuck on
"Starting show plymouth boot screen"
Decided to edit the GRUB file and remove the "no splash", so that I could see the console output while bootup up. There I noticed that the Light Display Manager was not starting. Checked this with systemctl status lightdm.service and indeed it failed to start.
Tried re-installing, tried dpkg-reconfigure lightdm, tried rebooting.. all did not work.
So another option is to switch to gdm3. Well, gdm3 was not installed and when I tried to I got an error that some packages were not installed. (Since I am on a different computer, I cannot copy-paste the console output.. So I will only state the most important information)
The following packages have unmet dependencies: gdm3: Depends: gnome-session-bin (but is not going to be installed) Depends: gnome-shell (but is not going to be installed) Recommends: xserver-xephyr (but is not going to be installed) Recommends: xserver-xorg Recommends: zenity (but is not going to be installed)
I read online that to circumvent the (but is not going to be installed) is to do something like
sudo apt-get install gdm3 gnome-session-bin gnome-shell xserver-xephyr zenity
But that just gives me a list of MORE dependencies from those packages... which ends up in an almost endless list of dependencies..
In such a case I would hope that sudo apt install -f or something along the lines of --fix-broken would do the trick.. but to no avail.
Somewhere in my gut I have the feeling that this is the fault of some nvidia driver messing things up.
But when I check my installed driver with grep "X Driver" /var/log/Xorg.0.log I see that I have version 460 installed (which is also the recommended driver by ubuntu-driver devices). However, when I try to check nvidia-smi I get as reply "...couldnt communicate with the NVIDIA driver".
Anyway, to conclude... Light Service DM is not starting. I have tried fixing it via GDM3, was stopped by broken packages. I think that somehow NVIDIA is involved, but I am not sure. Where to start from here?
1 Answer
I got to Ubuntu 20.04 via an updated Ubuntu 18.04. I think something went wrong there. I did a fresh install after I did my backup of course.
Now everything works smooth again.
