Debian 9+ MATE Desktop LightDM - Change lock screen background wallpaper
To change the default lock screen wallpaper in Debian 9 with MATE Desktop using LightDM as the lock screen manager could one expect would be easy. You just go to the settings somewhere and graphically select a picture and done. No. As of 2018-06 with mate-screensaver 1.16.1 there is no dialog available and you have to be root to do it by changing symbolic links. But you can do it. Open a terminal and do this: sudo bash cd /etc/alternatives Check the current lock screen so you know what you are trying to remove by pressing Windows + L. Unlock it and do this: mv desktop-background desktop-background-OFF Lock it again with Windows + L, now the background should be replaced by some gradient colors. If the image is gone, then you are half ways. Unlock it and set the picture you want: ln -s /path/to/your/image.jpg desktop-background Lock the screen again and have a look. For more information, see the ongoing discussion since 2014(!) about the missing feature: https://github.com/mate-desktop/mate-screensaver/issues/55
This is a personal note. Last updated: 2018-06-25 23:01:47.