# NSD Zone Files

## Adding records to zone files

Suppose you want to create an entry for `subdomain.example.com`.

First, open up the file `/var/nsd/zones/master/example.com` and add these two lines:

    subdomain    3600    IN      A       38.87.162.8  
                 3600    IN      AAAA    2602:fccf:1:1008::


Then, you will want to update the serial number in the Start of Authority record:

    $ORIGIN example.com.
    example.com.     3600   SOA   ns1.example.com. admin.example.com. (
                                2021072701   ; serial YYYYMMDDnn
                                1800        ; refresh
                                3600         ; retry
                                86400       ; expire
                                3600 )      ; minimum TTL


The serial number in a zone file is written in this form: `YYYYMMDDnn`.

`YYYY` is the year, `MM` is the month, `DD` is the day, and `nn` are two digits.

Here, `2021072701` tells us that this zone was written on July 27th, 2021.

It was the 1st edit of that day.

After you add records, make sure to increase the serial number to the correct

day. If multiple edits are made on the same day, increase the two-digit number by

one.

Then, run `doas nsd-control reload` to reload the zone files.

## Test the Results

After you update the zone file, make sure to test that the record has been updated:

    $ host subdomain.example.com
    example.com has address 192.168.0.1
    example.com has IPv6 address 2001:db8::


## $ORIGIN

See the [FQDN](/dns/FQDN) section.

## Start of Authority

The start of authority record:

    example.com.     3600   SOA   ns1.example.com. admin.example.com. (


`ns1.example.com.` needs to be replaced by the nameserver responsible for this zone. `admin.example.com.` means that the email for the sysadmin responsible for this zone is `admin@example.com`. Note that the @ ("at") symbol is replaced with a period.