Why is plymouth required?

Why is plymouth so important that cannot be removed on ubuntu desktop 11.04?

It has priority required and mountall and cryptsetup depend on it.

I do not have really any need to remove it, but a friend asked, so I am just curious.

Solution 1:

As htorque noted in the comments, if you remove the plymouth-theme-* packages you will not have a graphical boot. Ubuntu Developer, Upstart author, former Canonical employee, and current Googler Scott James Remnant wrote in a relevant bug report that "without them Plymouth merely regulates access to the system console in cases of filesystem decryption and error."

Ubuntu and Debain developer Steve Langasek adds in a message to the Debian development mailing list:

One of these days I'll get around to writing that blog entry to set the record straight on why plymouth is an indispensible component of boot with any modern boot system, because when everything is starting in parallel, you need something to handle I/O multiplexing to the user on console. So in a real sense, it should be a dependency. Even if you don't care about splash, you still need multiplexing.