When I try to run one of these commands:

sudo service gdm restart
sudo service gdm3 restart

the system gets stuck in a loop. It goes from the graphical interface to a black screen, then a terminal-like screen with lots of [ OK ] and then again GUI, this repeats cca every second.

It is impossible to stop this, as GUI ceases to respond to any keystrokes and tty randomly misses some of them (so that it's not possible to correctly input the password).

What is the correct procedure for restarting X then?
(I'm on a freshly installed Ubuntu 18.04 on Acer A315)

  • 1
    I think the new command is sudo systemctl restart gdm.service as Ubuntu can be using systemd
    – user690429
    May 15, 2018 at 6:33
  • @SmitTheLastFirefoxUser That does the same thing for me...
    – m93a
    May 15, 2018 at 7:24
  • I don't why but this should work if Ubuntu is using systemd as this works for me in arch Linux with systemd. Look like Ubuntu does something else behind the scenes that I am yet to find.
    – user690429
    May 15, 2018 at 7:28
  • This was an issue too in Solus Linux - This was solved there after update of gdm and after update of NVIDIA drivers with update of gnome - this issue is caused by a bug in NVIDIA. Oct 1, 2018 at 22:10

2 Answers 2


gdm may be buggy.

As a workaround, I use lightdm.

sudo dpkg-reconfigure lightdm

Choose lightdm as the display manager. And X restart works.

sudo service lightdm restart
  • I must agree with you. It's quite rare to reproduce the same behavior two or more times, even in a good scenario. Apr 5, 2022 at 16:03

Go Ctrl-Alt-F6 to get a tty;

then follow @Vajira Prabuddhaka at: GDM3 does not start in Ubuntu 18.04

sudo apt install ubuntu-gnome-desktop


sudo gnome-shell gnome


sudo systemctl restart gdm3

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