Can't we detect systemd by checking of the file `/usr/bin/systemctl` exists? Or `/etc/systemd/system.conf` or some other file that definitely exists on a systemd system. Probably the same for upstart. This avoids the parsing of os-release (if we wanted to do parsing, we should probably do it right, read line-wise, split key, value at first "=" and then compare key to NAME and check if openSUSE/Fedora is in value, etc..