# Systemd
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

systemd is the init system and service manager for most Linux distributions (since ~2015). It manages services, sockets, timers, mounts, and devices via unit files. `systemctl start/stop/enable/disable service`. systemd unified Linux service management across distributions, replacing SysV init and Upstart.

## Core Explanation

Unit types: service (.service), socket (.socket), timer (.timer, replaces cron), mount, target (group). `systemctl status service` shows state, logs. `journalctl -u service` views logs. Service unit example: `[Service] ExecStart=/usr/bin/app` with `Restart=always`. systemd starts services in parallel (not sequentially like SysV) — faster boot. Controversy: monolithic design, PID 1 complexity.

## Further Reading

- [systemd Documentation](undefined)