Re: @jerky_rs read the documentation
Oh, B. S.
All of the necessary documentation for SysVInit contained in a 2-page document, which is clear, concise, and easy to understand in all of its nuances, because SysVInit is the epitome of elegance. The systemd documentation runs into the hundreds of pages, and is anything but clear and concise.
I've been using Unix since 1983, WROTE a unix-like operating system in a matter of weeks in a senior-class assignment, and have been administrating Unix and Linux machines since the early 1990's. When I say systemd is an over-complicated pile of rubbish, it's NOT due to an inability to comprehend, it's due to the fact that Poettering is not nearly as talented as he believes himself to be, and thinks that "more lines of code" == "better code" when, in fact, the exact opposite is generally true.