systemd is the init system and service manager on most modern Linux distros. It is usually PID 1, so it starts the machine, brings up services, and keeps them running.
systemctl is the CLI you use to manage systemd units.
What this gives you access to:
- services that start on boot
- restart policies for crashed processes
- timers instead of cron for scheduled jobs
- logs through
journalctl - user services, if you want per-user daemons
For a devbox, the useful bit is simple: put your process in a .service file, enable it, and systemd will start it after reboot.
That makes it a good fit for keeping a Claude session runner, a helper daemon, or any other always-on process alive even after the box reboots. tmux helps with reattaching to a session, but systemd is what makes the process come back.
[Service]
ExecStart=/usr/local/bin/my-app
Restart=alwaysThen enable it with systemctl enable --now my-app.service.
If I need a process to survive reboots, systemd is usually the first thing to reach for.