IPv4 rDNS
Note: This example assumes your address is 192.168.1.1 which isn't a valid internet address. Your rDNS should use your actual internet address, so replace 1.1.168.192 with the reverse of your internet address.
In /var/nsd/etc/nsd.conf:
zone:
name: "1.1.168.192.in-addr.arpa"
zonefile: "master/1.1.168.192.in-addr.arpa"
(:ifend:)
In /var/nsd/zones/master/1.1.168.192.in-addr.arpa:
$ORIGIN 1.1.168.192.in-addr.arpa.
@ 3600 IN SOA ns1.username.example.com. admin.username.example.com. (
2021072300 ; serial YYYYMMDDnn
3600 ; refresh
3600 ; retry
86400 ; expire
3600 ) ; minimum TTL
3600 IN NS ns1.username.example.com.
3600 IN NS ns2.username.example.com.
@ 3600 IN PTR username.example.com.