To change the GDM (lock/login screen) theme, you need to replace the system's _default_ GNOME Shell theme.
## :warning: Cautions :warning:
- If the replacement fails, your desktop environment will not work properly. So please **be careful** if doing this.
- When applying this, other third-party GNOME Shell themes would look broken until you restore to the original theme.
- If GNOME Shell has been updated and restored to the original theme, you will need to install this again.
> Note: On Arch Linux, you can automatically reinstall the GDM theme by creating a [hook](https://wiki.archlinux.org/index.php/Pacman#Hooks) file. For example, if you use oomox-darker-compact as your GDM theme, put [this file](https://gist.github.com/looselyrigorous/a1aa931ce48627cc39daccc9253b30c7) in the `/usr/share/libalpm/hooks/` directory.
- `glib-compile-resources` — The package name depends on the distro.
- `glib2` (Arch Linux)
- `glib2-devel` (Fedora, openSUSE, etc.)
- `libglib2.0-dev` (Debian, Ubuntu, etc.)
- `libxml2-utils` — Ubuntu users only.
1. **Back up** the original theme file(s) first. If you are already using a custom GDM theme, skip this: