omd.service is created in
/etc/systemd/system/, which is being overwritten everytime Checkmk is updated. Instead, the package should create the service in
/usr/lib/systemd/system/, which will work exactly the same, except that if a service with the same name exists in
/etc/systemd/system/, it will use that configuration instead. This allows us to customize the
omd.service file without risking it being overwritten every update.
There is already a good explanation about the difference here: