I've just upgraded to 2.2.0 and noticed that knot failed to start. Upon inspection, I found that: /usr/lib/systemd/system/knot.service had the following line: ExecStartPre=/usr/sbin/knotc checkconf I think this is an error. I had to modify it to: ExecStartPre=/usr/sbin/knotc conf-check and then reimport the knot.conf file to get knot to start successfully.