Linux Administration Cookbook

Other init systems

systemd might be the dominant init system in the Linux world, but there are others that you'll still come across. At the time of writing, CentOS 6 is very much alive and kicking, with its upstart core.

That's without going into the nitty-gritty of what the BSDs use and macOS to boot (which I actually quite like).

I have seen some absolutely ancient Debian installations in my time, some of which went out of support half a decade or longer ago. I once worked out that a box I was SSH'd into, could legally drive.