Plymouth is an application that runs very early in the boot process (even before the root filesystem is mounted!) that provides a graphical boot animation while the boot process happens in the background.
I am sharing my own Plymouth's theme. It was based on a older image that I always loved to use. I generated this theme to replace my default Plymouth Kubuntu theme. It was tested on KUbuntu 20.04.
This theme displays system messages in a central box, which is also the place to receive the password (for encrypted devices).
$ sudo apt-get install git build-essential debhelper devscripts
$ mkdir ~/plymouth-theme
$ cd ~/plymouth-theme
$ git clone https://github.com/jeiks/plymouth-theme.git
$ cd plymouth-theme
$ debuild -sa -d
$ cd ..
$ sudo dpkg -i plymouth-jeiks-theme_1.0.1_amd64.deb
Installing this package (.deb file) is a good option, because the package will automatically set this theme as default and also update the initramfs file.
If you need, you can check if the different-tux theme is the default by using the following command:
$ sudo update-alternatives --config default.plymouth
And you have to see the different-tux theme masked with an asterisk (*):
There are 2 choices for the alternative default.plymouth (providing /usr/share/plymouth/themes/default.plymouth).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/share/plymouth/themes/different-tux/different-tux.plymouth 200 auto mode
1 /usr/share/plymouth/themes/different-tux/different-tux.plymouth 200 manual mode
2 /usr/share/plymouth/themes/kubuntu-logo/kubuntu-logo.plymouth 150 manual mode
Press <enter> to keep the current choice[*], or type selection number:
To select other theme, you must type the desired theme number and press ENTER.
And to remove the package (and theme):
sudo dpkg -r plymouth-jeiks-theme
You have to follow these steps (the explantion is on shell comments, i.e., lines starting with "#"):
# Install git, clone this repository and enter on this cloned folder:
$ sudo apt-get install git
$ cd /tmp
$ git clone https://github.com/jeiks/plymouth-theme.git
$ cd plymouth-theme
# Installing the different-tux directory on /usr/share/plymouth/themes:
$ sudo make install
# Creating an alternative to select different tux as Plymouth's default theme:
$ sudo update-alternatives --install \
/usr/share/plymouth/themes/default.plymouth default.plymouth \
/usr/share/plymouth/themes/different-tux/different-tux.plymouth 200
# Cheking if it is the default (it has to be marked by an asterisk "*"):
$ sudo update-alternatives --config default.plymouth
# Updating the initramfs
$ sudo update-initramfs -u
And to remove:
$ sudo update-alternatives --remove default.plymouth \
/usr/share/plymouth/themes/different-tux/different-tux.plymouth
$ sudo update-initramfs -u
$ sudo rm -rf /usr/share/plymouth/themes/different-tux