systemd

systemd 1 is an init system and service manager for Linux systems. It is the first process to start (PID 1), manages the boot sequence and oversees all aspects of the lifecycle of services under its control.

The different types of “things” systemd can manage are called "units".

Although a few other init systems are still in use (like OpenRC), the vast majority of Linux distributions now uses systemd.

Managing systemd

If you need to administer a machine running systemd, the following resources may be of interest to you:

  1. The official spelling is systemd, all lowercase. Even at the start of a sentence. The authors are pretty picky about it too, as the following has been displayed rather prominently on their homepage: _“Yes, it is written systemd, not system D or System D, or even SystemD. And it isn’t system d either. Why? Because it’s a system daemon, and under Unix/Linux those are in lower case, and get suffixed with a lower case d. And since systemd manages the system, it’s called systemd. It’s that simple. But then again, if all that appears too simple to you, call it (but never spell it!) System Five Hundred since D is the roman numeral for 500 (this also clarifies the relation to System V, right?). The only situation where we find it OK to use an uppercase letter in the name (but don’t like it either) is if you start a sentence with systemd. On high holidays you may also spell it sÿstëmd. But then again, Système D is not an acceptable spelling and something completely different (though kinda fitting).” ↩︎