While testing different configurations for bug #526 I set `zonefile-sync: -1` to force knot to keep all zone data in the journal, and never write out zone files. The documentation suggests that I should still be able to flush a zone manually if I want to. So I ran `knotc zone-flush ipv6actnow.org`. In the log I see: ``` 2017-07-22T08:50:00 info: [ipv6actnow.org.] control, received command 'zone-flush' ``` However, there is no zone file in the storage directory (/var/knot) Then, I tried `knotc zone-flush ipv6actnow.org +outdir /tmp`. This time, as expected, knot wrote the zonefile into /tmp. So finally, I tried `knotc zone-flush ipv6actnow.org +outdir /var/knot` and explicitly gave it the path to the storage directory. This time, the zone file was written. So it looks like there is a subtle bug that prevents flushing the zone to the storage directory when zonefile-sync is set to -1.