systemd is the init system on many Linux distros. It starts services (units), manages dependencies, logs to the journal, and handles targets (boot states).
List units:
systemctl list-units
systemctl list-units --type=service
systemctl list-unit-files --type=service
Service lifecycle:
sudo systemctl start nginx
sudo systemctl stop nginx
sudo systemctl restart nginx
sudo systemctl reload nginx
systemctl status nginx
Enable at boot:
sudo systemctl enable nginx
sudo systemctl disable nginx
journalctl -u nginx
journalctl -u nginx -f
/lib/systemd/system/ or /usr/lib/systemd/system//etc/systemd/system/Reload after unit changes:
sudo systemctl daemon-reload
sudo systemctl restart <unit>