systemd: Services, Logs and Timers¶

Everyday commands¶

systemctl status nginx
sudo systemctl enable --now nginx
sudo systemctl restart nginx
systemctl list-units --failed
sudo systemctl daemon-reload          # after editing unit files

Logs with journalctl¶

journalctl -u nginx -f                       # follow
journalctl -u nginx --since "1 hour ago"
journalctl -p err -b                         # errors since boot
journalctl -b -1                             # previous boot

A service unit with sensible hardening¶

/etc/systemd/system/demo-api.service

[Unit]
Description=Demo API
After=network-online.target
Wants=network-online.target

[Service]
User=demo
ExecStart=/usr/local/bin/demo-api
Restart=on-failure
RestartSec=5
NoNewPrivileges=true
ProtectSystem=strict
ProtectHome=true
PrivateTmp=true
ReadWritePaths=/var/lib/demo

[Install]
WantedBy=multi-user.target

Timers (a modern cron)¶

backup.timer

[Timer]
OnCalendar=*-*-* 02:00:00
Persistent=true

[Install]
WantedBy=timers.target

It runs a matching backup.service. Check with systemctl list-timers. Persistent=true runs a missed job after downtime.

Slow boots¶

systemd-analyze blame | head
systemd-analyze critical-chain