Glossary

systemd

The init system that starts and supervises services on modern Linux.

systemd is PID 1 on most current distributions: it boots the machine, starts services in dependency order, restarts them when they fail, and captures their logs. Services are declared as "unit" files rather than shell scripts.

You interact with it through systemctl (start, stop, enable, status) and journalctl (its logs). Because it places each service's processes in a cgroup, stopping a service reliably stops everything it spawned — a real improvement over the init scripts it replaced.

See it in practice

$ systemctl status nginx && journalctl -u nginx -n 20

State plus recent logs — the standard two-step diagnosis for any service.

Where you'll meet it