Tired of seeing the purple background when you’re entering your password? Well, you can change that!

The first thing that you’ll want to do is move the picture (FWIW, I’ve had no luck with copying) to a readable location. In this instance, Ubuntu already comes with one; so, we’ll move the photo to there.

sudo mv ~/Bilder/SvenskaFlagga/RYM4a8.jpg /usr/share/backgrounds/

After that, we need to edit the CSS file that is used to reference the photo for the login screen. To do this, we’ll open it in our chosen editor:

sudo nano /etc/alternatives/gdm3.css

You’ll look for the lock screen dialogue to modify. The easiest way to find it is Ctrl + Shift + – (Ctrl + _) and go to row 1814 (as of the writing of this).

#lockDialogGroup {
  background: #2c001e url(resource:///org/gnome/shell/theme/noise-texture.png);
  background-repeat: repeat; }

Replace it the data in the url field with the file you just copied, being sure you change to it from resource to file. You need to change the background-repeat field and add two fields, as well, to accomplish this.

#lockDialogGroup {
  background: #2c001e url(file:///usr/share/backgrounds/RYM4a8.jpg);
  background-repeat: no-repeat;
  background-size: cover;
  background-position: center; }

Press Ctrl + X to start exiting nano and enter your language’s confirmation letter (e.g.: ‘Y’ for English, ‘J’ for Swedish, etc.) and press Enter.

Now, reboot the machine and your chosen login background will show when you attempt to login. 🙂

Thanks for coming to this NERDTalkT and happy Ubuntuing!