How to change Ubuntu Budgie login screen background?

I have simple Ubuntu 18.04.1

In my opinion the best way to do this:

step1: make backup of the file /usr/share/gnome-shell/theme/ubuntu.css - if you have another desktop for ubuntu you can find file ubuntu.css just using command locate ==> locate ubuntu.css

step2: vim /usr/share/gnome-shell/theme/ubuntu.css and find part below

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

step3: change it to

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

clarification: as you can see, we changed
"background: #2c001e url(resource://" part to the ==> "background: #2c001e url(file://"
and then set up path for the image.
I used /usr/share/backgrounds/ for the path with image. Also I added some css properties to center the image.

This is only the css file configuration. That's it)

Open the Login Window app in the menu under Administration.

If it is missing from the menu then install it:

sudo apt install lightdm-settings

Enter your credentials when prompted. Click on the default background image icon, then navigate to /. Click on home>username>Pictures. Select your desired pic, click Open the in upper right corner, close the app. Log off and you will see your desktop background on the Login screen.

Thanks.

I tried all of those and none worked. This does, for sure:

As root user, just copy your_image.png to /usr/share/backgrounds and ....

# cd /usr/share/backgrounds
# cp warty-final-ubuntu.png warty-final-ubuntu.png.stock
# rm warty-final-ubuntu.png
# ln -s your_image.png warty-final-ubuntu.png
# reboot

...where your_image.png is the name of the actual image you want to display. The warty one is big: 4096 x 2304. I matched mine to the same size.

had the same problem when upgrading to 18.04. 64bit. And the answer is, it depends. Start with 'cat /etc/X11/default-display-manager' and check which greeter manager you got.

Case1. If using gnome-greeter (gdm3, and for example with ubuntu-unity-desktop which is in my case) modify the ubuntu.css as mentioned before and make sure you have replaced 'resource' ident by 'file', otherwise it won't work no matter how hard you try (i promise). Restart your machine. (gnome-tweak-tool works for modifying the background etc.)

Case2. If using the lightdm greeter one can use 'sudo apt install lightdm-gtk-greeter-settings' an adapt changes as needed. Two alternatives are the dconf editor (search for 'greeter', what will show you all the config settings available, and the 'sudo apt install unity-tweak-tool'.

Change between your greeter managers and the different ways changing styles with 'sudo dpkg-reconfigure lightdm' or 'sudo dpkg-reconfigure gdm3'.

Hope it helps

lightdm-settings is a good choice, as well as, you can try

sudo xhost +SI:localuser:lightdm
sudo su lightdm -s /bin/bash
dconf-editor

In dconf-editor find x/dm/slick-greeter you can edit whatever you want

Cheers

• Run Terminal with Ctrl + Alt + T
• Run nautilus with sudo by doing (sudo nautilus) - without the brackets
• Copy your desired background image to /usr/share/backgrounds/
• Go to /etc/alternatives/gdm3.css and open with Text Editor

Change This

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

To This

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

Click 'Save' when you're done.

Restart your PC

After the upgrade to 18.04 I was unable to change the login/lock screen too. So I just replaced the warty-final-ubuntu.png in /usr/share/backgrounds using sudo nautilus with a picture with the same resolution 4096x2304. I renamed it the same : warty-final-ubuntu.png, and deleted the old one. This was fastest and easiest solution...

(ubuntu 18.04 after updates.)

I installed ligthdm, cannot start because of a missing library.

I've renamed the myimage.png to warty-final-ubuntu.png in /usr/share/background. myimage.png has same resolution as warty. It does't work either. And have to go in recovery mode to change as it was, to be able to get to the login screen agin.

Then, I've changed #lockDialogGroup in ubuntu.css to:
... url(file:///usr/share/backgrounds/myimage.png) ...
I doesn't work either. And had to recover again. then I gave up.

Last idea, changed myimage.png to anoter image in jpg format: myimage.jpg. Rebooted instad of log out first. After the reboot, it works.

1. Install gnome-tweak-tool: sudo apt install gnome-tweak-tool

2. Click on the app grid icon, type in: gnome-tweak-tool

3. Open (click on) the gnome-tweak-tool app.

4. Click on "Appearance".

5. On the right-hand pane, find "Background." Click on "image" below it and find the jpg file you want for your Ubuntu background.

6. On the right-hand pane, find "Lock Screen." Click on "image" below it and find the jpg file you want for your Lock Screen page.

Lots of other tools in gnome-tweak-tool that you might like, also.