The hostname of this ncdns instance, which defaults to the machine hostname. If specified, ncdns lists the hostname as an NS record at the zone apex: bit. IN NS ns1.example.com. If unset ncdns will generate an internal pseudo-hostname under the zone, which will resolve to the value of services.ncdns.identity.address. If you are only using ncdns locally you can ignore this.

config.networking.hostName

"example.com"