Init System
Gentoo's init system is another important feature. It is similar to the System V init system that most Linux distributions use, but uses dependency-based scripts and named run levels rather than numbered ones. It also includes a command called rc-update which manages runlevels.
Gentoo startup scripts use the runscript shell interpreter, rather than a more traditional shell.
Originally Gentoo's rc system was written entirely in Bash and was part of the baselayout package, which contains the basic filesystem layout and critical files needed for the system. However, this led to several limitations. For example, certain system calls needed to be accessed during boot which required C-based callouts to be added. These callouts were each statically linked, causing the rc system to bloat over time. Additionally, as Gentoo expanded to other platforms such as Gentoo/FreeBSD and Gentoo Embedded, requiring the relatively heavy Bash shell for the rc system became undesirable or sometimes impossible.
This led to a development of baselayout 2, which was written in C and only required a POSIX-compliant shell. During this development, it was decided that it was a better fit if baselayout provided only the base files and filesystem layout for Gentoo, and the rc system was broken off into an independent project – OpenRC.
Read more about this topic: Gentoo Linux
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