How can I change the purple background color of the lock screen on Ubuntu 17.10?

Question

Recently I installed Ubuntu 17.10 which comes with Gnome as the default DE and I like it a lot but cannot figure out how to change the purple background of the lock screen (when typing in the password).

I've tried reconfiguring GDM but it seems to be different and it only affects the login screen.

If there is no solution I'm interested in ANY workaround because this purple drives me crazy but I don't want to drop GNOME entirely just because of this. Any help is highly appreciated.

Answer 1

From these steps here, you can change both the image and the background colour:

1. Move your favorite image to /usr/share/backgrounds:

   • It's better to move the image you want to set as login background to system pictures folder: /usr/share/backgrounds. To do so, open terminal via Ctrl+Alt+T, then either run command:

     sudo cp /PATH/TO/IMAGE /usr/share/backgrounds/
     

2. Edit the css file that define GDM login background:

   • Open terminal (Ctrl+Alt+T) and run command to edit file /etc/alternatives/gdm3.css, which is linked to /usr/share/gnome-shell/theme/gdm3.css:

     # Make backup first before editing
     sudo cp /etc/alternatives/gdm3.css /etc/alternatives/gdm3.css.bakup
     sudo nano /etc/alternatives/gdm3.css
     

     

3. When the file opens, go to menu (right after ‘Save’ button) -> find and find out following section:

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

   change the lines into:

   #lockDialogGroup {
      background: #000000 url(file:///usr/share/backgrounds/Aardvark_Wallpaper_Grey_4096x2304.png);
      background-repeat: no-repeat;
      background-size: cover;
      background-position: center; }
   

   Replace Aardvark_Wallpaper_Grey_4096x2304.png with your picture file name, and or change the hex colour code ##2c001e to the color of your choice.Here I used black.

   

Lockscreen background:

Note: Backup all files before changing them

Answer 2

Run: sudo update-alternatives --config gdm3.css and choose the option 1 (or the one with the path to gnome-shell.css file) as seen below:

Reboot and Ok, you're good to go.

Answer 3

In a shell, type:

sudo update-alternatives --config gdm3.css

You will get a screen asking for alternative gdm3.css. Select the one with gnome-shell.css.