Query and control units on systemd hosts.

systemctl

Is it enabled across reboots

systemctl is-enabled nginx
systemctl is-active nginx

These answer different questions. is-active says it is running now, is-enabled says it starts on boot.

Read the log without journalctl guesswork

journalctl -u nginx -n 50 --no-pager

See why a unit failed

systemctl status nginx --no-pager -l

Reload after a config change

nginx -t && systemctl reload nginx

&& matters: reloading a broken config takes the service down on some units.

Scope: systemctl