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