LFS201 - Chapter 23 Discussion // Questions // Banter - Kernel Services and Configuration

It works on CentOS 7, CentOS 8 and Ubuntu 20.04 (I checked) and is part of the base "man-pages" package, so I don't know why it would not be on your system if it is any normal linux distribution (not one pared back to not have man). You can also find the man-pages on the Internet, in particular this one at:

https://man7.org/linux/man-pages/man7/bootparam.7.html

ah, you have stumbled on systemd command line parameters which are different than kernel command line parameters (the man kernel-command-line is part of the systemd package)

The way things work is any parameter on the kernel command line is sent to the kernel first. If the kernel does not appreciate the parameter it then gets passed to PID=1, which these days is systemd-init and then is interpreted by systemd.

It's confusing and the source of some really nasty fights in the past between some kernel developers and some systemd people, but we avoid holy wars.

As a simple example, if you give just a "3" on the command line, the kernel ignores it and it tells init to go to run level 3 (no GUI desktop)