Disclaimer

This script is provided as is, with no warranty whatsoever. There is a risk of bricking your installation if you mess around with the wrong files. Be prepared to get your hands dirty!

This script is only tested on my Pop!_OS 20.04 LTS x86_64 installation (i.e. it works on my PC). Your mileage may vary, especially if you are not using Pop.

Initial setup

• Fork, clone, and cd into this repo.

• Run update-alternatives --get-selections | grep gdm3-theme.gresource to find out which gnome-shell-theme.gresource file is currently being used.

• Run cp </path/to/gnome-shell-theme.gresource/> gnome-shell-theme.gresource.backup to create your very own backup of gnome-shell-theme.gresource. (Note: you might need to invoke sudo here).

• Run cp gnome-shell-theme.gresource.backup gnome-shell-theme.gresource; this creates a copy that we will be working with.

• Edit the WORKDIR variable in utils/extract.sh and utils/compile.sh to point to where you cloned the repo.

• At this point you would want to probably commit and push to your own fork as a safe point.

Usage

• Run ./utils/extract.sh. This extracts the gresource binary into the folder theme.

• Your entry to most edits should be on gdm3.css (e.g. to change login screen background) and / or gnome-shell.css (e.g. to change shell related stuff). DO NOT remove the @import statements at the top of these files!

• You can extend this to other files that you need to edit as well, by adding a -original suffix to the name of the original css file, creating a new css file with the original name, and then importing the original file. The extract.sh script assumes you will only edit gdm3.css and gnome-shell.css, so adjust accordingly if you change things.

• Once done, run ./utils/compile.sh to create a new gnome-shell-theme.gresource binary that you should copy to where gdm3-theme.gresource points to (see step 2 of Initial setup).

• Reboot (Alt + F2 followed by typing reboot and hitting Enter) your PC for changes to take effect.

Troubleshooting

• If you brick your installation, your best bet is to probably boot from a live USB, and mount your original installation by following the steps here. Once you do so, try and undo the breaking change you introduced.

Links that I found useful while writing this script

• change GNOME 3.36 gdm3 lock screen (screen shield) font colour - what css selector to target in gdm3.css?
• How do I change login screen theme or background in Ubuntu 20.04?
• How to customize Gnome login screen in Debian
• PRATAP-KUMAR/focalgdm3