OS: Ubuntu (Gnome) 16.04
NOTE: This does only seem to affect (as far as I know) Nvidia GPU users.
When booting you see your screen for no more than a few seconds and then it seems to "restart" and repeat itself. The message on the screen for a brief moment is "Stopping User Manager for UID 121".
I had this issue and determined that it was the Nvidia drivers. For some reason they did not take well with an Ubuntu update. During the update one of the things updated was xorg and linux-headers; I think it is possible that one of these is to blame. However, instead of laying blame, I would rather find a solution, which I seem to have. Here is what I did.
Solution: (I think)
- Booted into GRUB.
- GRUB: Selected Advanced options for Ubuntu
- GRUB: Selected latest recovery module. ("Ubuntu, with Linux 4.4.0-43-generic (recovery mode)")
- Recovery Menu: Selected networking. (To enable network access)
- Recovery Menu: Selected dpkg. (To attempt to update any needed packages)
- Recovery Menu: Selected root. (Get root access)
- You need to determine in what directory you want to download a new driver file.
- cd <to_prefered_directory>
- wget <NVIDIA_driver_URL> (See URL below)
- chmod a+x <NVIDIA_driver_FILE>
- Follow the prompt. If you are running a 64-bit system. Ignore the 32-bit warning.
Nvidia 367.57 Driver URL:
That's it. You should be able to reboot your system and select your Ubuntu installation and boot like normal. I did notice a slightly slower response when starting back up. But once that was done it ran like a champ again.
PS: If you are experiencing this issue over again. Try to update your system while you are in it. If that does not work try these instructions for a second time. I have found that sometimes repeating these steps works. I also found that sometimes it takes a moment for the update (if any) actually take affect.