The file that contains information about a 'Zone' (a DNS domain).
For instance there is a ".co.nz" zonefile that holds information about where to look for all the *.co.nz domains.
which sets the default TTL for records that don't have one.
$ORIGIN domain
which specifies the domain to add to a record that doesn't have one.
A Zone file can also contain comments, which are lines that start with a semicolon.
Otherwise a zone file contains 'resource records' which are an optional name, an optional TTL, an optional class (The only one you'll ever use is IN for Internet, others exist such as CH for Chaos, but noone uses them), the resource record type and any parameters it requires.
If the name is omitted then the name of the previous record is used, if the TTL is omitted the default TTL (as specified by $TTL) is used, the default class can be specified in the name server configuration.
dom.ain IN SOA (
primary.name.server ; The name of the primary name server for this domain contact.email.address ; an email address of someone to contact about this zone, with the "@" replaced with a "." serialnumber ; the revision number of this zone, incrimented every time there is a change refresh.timeout ; after the refresh timeout has expired a secondary will check the primary for an updated serial retry.timeout ; if the refresh fails, it will retry after retry.timeout expire.timeout ; if a refresh/retries has failed after the expire timeout expires the secondary will become a LameNameServer? negative TTL ; the TTL to use on the 'no such domain' reply )
7 pages link to ZoneFile: