vim /etc/systemd/system/foo.service
chmod +x /etc/systemd/system/foo.service

ExecStart=/bin/bash echo "Hello World!"

systemctl daemon-reload
systemctl start foo

You can also use systemctl cat nginx.service to simply view how the init script starts the service

To enable and start a service in the same line you can do

systemctl enable --now foo.service

To check if service is enabled

systemctl is-enabled foo.service; echo $?

To check the services that start with the OS in order you can do

systemctl list-units --type=target



List failed services

systemctl --failed
journalctl -p 3 -xb

To filter only 1 service you will need to use the flag -u

journalctl -u nginx.service

To have live logs on a service you can do

journalctl -f _SYSTEMD_UNIT=nginx.service

To have live-tail logs for 2 services example nginx and ssh

journalctl -f _SYSTEMD_UNIT=nginx.service + _SYSTEMD_UNIT=sshd.service

To check logs since the latest boot:

journalctl -b

To get the data from yesterday

journalctl --since yesterday
journalctl -u nginx.service --since yesterday

To view kernel messages

journalctl -k