feat: add doc/systemd-create-unit.md

doc/systemd-create-unit.md

@@ -0,0 +1,44 @@
+# Setup systemd unit
+
+* it is prudent to make sure none of the existing systemd unit files have the name we want to give our new service.
+```
+systemctl list-units --type=service
+```
+
+* create our unit file.
+```
+sudo vi /etc/systemd/system/<service name>.service
+```
+
+* paste text into the editor accoring to the <service name> needs
+
+* give the owner read and write permissions, and read permissions to the group. Others will have no permissions.
+```
+sudo chmod 640 /etc/systemd/system/<service name>.service
+```
+
+* check the syntax of our unit file for us, even if the service isn't running yet
+```
+systemctl status <service name>.service
+```
+
+* When you add a new unit file or edit an existing one, you must tell systemd to reload the unit file definitions.
+```
+sudo systemctl daemon-reload
+```
+
+* If you want a service to be launched at startup you must enable it:
+```
+sudo systemctl enable <service name>
+```
+
+* Enabling a service doesn't start it, it only sets it to be launched at boot time. To start the service now, you must use systemctl with the start option.
+```
+sudo systemctl start <service name>
+```
+
+* verify that our service is running correctly.
+```
+sudo systemctl status <service name>.service
+```
+