GDM Theme

You can change the GDM (lock/login screen) theme by replacing the default GNOME Shell theme.
However if it fails, your desktop environment may not operate correctly. So please be careful if doing this.

⚠️ Cautions:

• 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.

Installation

1. Back up the original theme file:

Note: If you are already using a custom GDM theme, skip this.

sudo cp -v /usr/share/gnome-shell/gnome-shell-theme.gresource{,~}

# for Ubuntu 17.10, you also need the following
sudo cp -v /usr/share/gnome-shell/theme/ubuntu.css{,~}

2. Select a GTK+ theme to decide which variant to install.
3. Replace the default theme file with the following commands:

GTK_THEME=$(gsettings get org.gnome.desktop.interface gtk-theme | sed "s/'//g")
sudo cp -v /usr/share{/themes/$GTK_THEME,}/gnome-shell/gnome-shell-theme.gresource

# for Ubuntu 17.10, you also need the following
sudo cp -v /usr/share/themes/$GTK_THEME/gnome-shell/gnome-shell.css /usr/share/gnome-shell/theme/ubuntu.css

4. Reload the theme.

If you are running GNOME Shell, press Alt + F2 then type rt.

Uninstallation

1. Restore to the original theme from the backup:

sudo mv -v /usr/share/gnome-shell/gnome-shell-theme.gresource{~,}

# for Ubuntu 17.10, you also need the following
sudo mv -v /usr/share/gnome-shell/theme/ubuntu.css{~,}

2. Reload the theme.

If you are running GNOME Shell, press Alt + F2 then type rt.