LightDM background image

Recently my old laptop, due to some unknown configuration, it shows a background image in the LightDM login. It is annoying, and it is user specific. Meaning, if I choose another user, the background image will be changed to black background.

Searched for the solution on Internet, most of links are about gsettings, or edit the image in /etc/lightdm/lightdm.conf. But none of the related to my issue.

Finally, I found the solution. The problem is not LightDM itself, but related to AccountsService.

To solve the issue, edit the /var/lib/AccountsService/users/[username], there is a line

[org.freedesktop.DisplayManager.AccountsService]
BackgroundFile='/path/to/custom/image.jpg'

That’s the culprit. Remove or comment out the BackgroundFile, then the problem solved.