The boot-up splash and login screen may be changed while trying out different desktop environments in Ubuntu, such as KDE, XFCE, LXDE. This quick tutorial is going to show you how to restore plymouth splash and LightDM login greeter to default if you messed them up.
Restore plymouth the splash screen to default:
Launch a terminal window from the dash or press Ctrl+Alt+T. Copy and paste this command into terminal and hit enter, it will display a list of installed plymouth themes. The Ubuntu default is “/lib/plymouth/themes/ubuntu-logo/ubuntu-logo.plymouth”, choose it.