How to restore plymouth default theme

Solution 1:

You can change the installed plymouth themes by typing the following command on Terminal:

sudo update-alternatives --config default.plymouth

You’re supposed to select your desired plymouth theme by typing its number and then press [Enter]. After choosing and activating your desired plymouth theme, you have to “save” the changes by typing the following command:
sudo update-initramfs -u

Solution 2:

You can use Plymouth Manager. It is a program that can be used for theming Plymouth (so, you can choose the default theme).

This is the PPA you need:

https://launchpad.net/~mefrio-g/+archive/plymouthmanager

To add the PPA and install the program:

sudo apt-add-repository ppa:mefrio-g/plymouthmanager
sudo apt-get update
sudo apt-get install plymouth-manager

Then, if you don´t want to keep Plymouth Manager:

sudo apt-get purge plymouth-manager
sudo add-apt-repository --remove ppa:mefrio-g/plymouthmanager

Last line is needed for removing the PPA.

Ariel