I was trying to change the background color of the login screen for the gnome desktop manager on Ubuntu 20 but i've made a mistake and now have a error on the login screen with the message 'Oh no! Something has gone wrong.' and now i'm unable to log in as usual. Is there any way to regenerate the original login screen file or somewhere to get another?

All of the resources i found for changing the theme spoke about changing lockDialogGroup in /usr/share/gnome-shell/theme/ubuntu.css, but i didn't have that on my version of Ubuntu. I was changing the hex values of lockDialogGroup in /usr/share/gnome-shell/theme/Yaru/gnome-shell-theme.gresource and then the error started occurring. I've used a tty shell to make sure the values are all ok but I must have entered a random character somewhere accidentally causing the error.

thanks in advance.

2 Answers 2


Found the error. I added an extra space after a closing parenthesis. If you are making any changes to the gnome-shell-theme.gresource i assume that the way it is written has to remain the same except for values such as color hex values.

#lockDialogGroup {
  background-color: #ffffff; }x 

the extra space causing the problem was where the x is

  • This didn't fix me....I tried changing it...do you have any other solution...or just I have to reinstall:( Commented Jul 12, 2020 at 6:22

My login screen was broken after using ubuntu-gdm-set-background. I was able to repair it by booting into recovery and using the console to execute the rescue statement which had wisely been shown by ubuntu-gdm-set-background. For Ubuntu 20.04 and 21.04 use

sudo update-alternatives --quiet --set gdm3-theme.gresource /usr/share/gnome-shell/theme/Yaru/gnome-shell-theme.gresource

and for 21.10 and 22.04 use

sudo update-alternatives --quiet --set gdm-theme.gresource /usr/share/gnome-shell/theme/Yaru/gnome-shell-theme.gresource

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