Plymouth is an application that runs right on time within the boot procedure (even before the root filesystem is mounted!) that gives a graphical boot animation whereas the boot procedure occurs in the background. Plymouth is a project from Fedora. It depends on kernel mode setting (KMS) and the frame buffer to set resolution of the display as early as possible, to show a boot screen.
Plymouth comes with two binaries: /sbin/plymouthd and /bin/plymouth. The first one is plymouthd and it do all the heavy work like logging the session and showing the splash screen. The second one is /bin/plymouth it controls the interface of plymouthd. It supports things like plymouth show-splash, plymouth ask-for-password.
For Meilix start by creating a theme directory inside the /usr/share/plymouth.We create two type of themes one with logo and one with text.The theme configuration file that is read by plymouthd is the name of the theme with a .plymouth extension. In this case it is meilix-logo.plymouth.
This theme calls the script plugin to do the actual work of displaying the theme. The script plugin expects image files with specific names. Various directives can be passed to plugin’s.Script plugin supports two basic objects, Image, and Sprite
Meilix logo Plymouth theme files and script link
For Plymouth text version we only need to make a single file using ubuntu-text plugin like this.
How do Plymouth know when to quit? actually it does not know when to quit so It just keeps on going until it receives a quit message. In the case of Meilix, the /etc/init.d/plymouth script sends the quit message.