#create then put your script (e.g. nginx) into /etc/init.d with root as user & group
sudo update-rc.d nginx defaults     -> loads the script
sudo update-rc.d nginx enable       -> enable the script to run at system sturtup/boot
service nginx start                 -> starts the service
service nginx status
systemctl -l status nginx
service --status-all                -> shows status for all services
systemctl                           -> shows all active units
systemctl list-units --type=service -> shows all active services (--all to see loaded but inactive services too)

# reload service's configuration:
sudo systemctl reload nginx.service