How to Create a systemd Service
systemd is the init system on every modern Linux. A service unit = .service file describing how to start/stop/restart a daemon. Replaces supervisord, pm2 (for Node), rc.d. Auto-start on boot, auto-restart on crash, journalctl for logs, systemctl for control. Minimal unit — 10 lines.
Below: step-by-step, working examples, common pitfalls, FAQ.
Step-by-Step Setup
- Create /etc/systemd/system/myapp.service
- [Unit] section: Description, After=network.target
- [Service] section: ExecStart, User, WorkingDirectory, Restart=on-failure
- [Install] WantedBy=multi-user.target
systemctl daemon-reload— reload unitssystemctl enable myapp— auto-start on bootsystemctl start myapp+systemctl status- Logs:
journalctl -u myapp -f(live tail)
Working Examples
| Scenario | Config |
|---|---|
| Simple Node.js service | [Unit]
Description=My App
After=network.target
[Service]
Type=simple
User=nodejs
WorkingDirectory=/opt/myapp
ExecStart=/usr/bin/node /opt/myapp/server.js
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target |
| Python with venv | [Service]
Type=simple
User=app
WorkingDirectory=/opt/myapp
ExecStart=/opt/myapp/venv/bin/python /opt/myapp/app.py
Environment="PATH=/opt/myapp/venv/bin"
Restart=on-failure |
| Systemd hardening (sandboxing) | [Service]
NoNewPrivileges=true
PrivateTmp=true
ProtectSystem=strict
ProtectHome=true
ReadWritePaths=/var/log/myapp |
| Timer (cron-like) | # /etc/systemd/system/backup.timer
[Timer]
OnCalendar=*-*-* 03:00:00
Persistent=true
[Install]
WantedBy=timers.target |
| Reload config without restart | ExecReload=/bin/kill -HUP $MAINPID
# systemctl reload myapp |
Common Pitfalls
- ExecStart with relative path — "not found". Always absolute /usr/bin/node
- Environment variables:
Environment="KEY=value", not bash syntax - User=root — anti-pattern. Create a dedicated user:
useradd -r -s /bin/false nodejs - Logs don't write to a file — they go to journald:
journalctl -u myapp - Missing
systemctl daemon-reloadafter a unit change → stale config
Learn more
Frequently Asked Questions
systemd vs pm2 / supervisord?
systemd — built-in Linux, zero deps. pm2 — specialized for Node.js (cluster, zero-downtime reload). For simple apps — systemd.
Which restart policy?
on-failure (restart on non-zero exit) — standard. always — restart even on normal exit (useful for daemons). no — manual only.
How to graceful shutdown?
<code>TimeoutStopSec=30s</code> — systemd waits 30 s before SIGKILL. App must handle SIGTERM and exit cleanly.
Logs get huge — rotation?
journald auto-rotates. Settings: <code>/etc/systemd/journald.conf</code> → SystemMaxUse=1G, MaxRetentionSec=30d.