Zone File Primer

[Alan Glennon]

Is there a good explanation online about Zone Files, what they are, what they contain, and how they are commonly used by domainers?

 

[katherine]

Look at this perhaps:
http://www.dnforum.com/threads/root-zone-file-splitting-extracting-etc.296102/

Traditionally, zone files are compared on a daily basis (against the previous "release") to produce lists of newly registered domains, and deleted domains.

They contain almost all domains registered in a given TLD. So you can for example use the data for many different purposes like data mining, building a search engine or directory etc.

 

[jmcc]

A basic (if slightly technical) explanation:
http://en.wikipedia.org/wiki/Zone_file

They generally contain active domain names and their nameservers, nameservers in that zone/TLD along with the IP addresses for the nameserver, DNSSEC data and some other stuff.

The stuff that domainers are interested in is the list of raw domain names. They extract them from the zone files using either Linux/Unix software (grep/sed/Perl or other languages) or Windows software. Then they generally compare the list of these domains against a previous list to see what domains have been dropped from the latest zone file. That requires a database (typically MySQL or similar) into which both lists of domains are loaded and then it is a case of executing some SQL statements to produce the new list or the dropped list.

While this kind of thing is easy enough for the new gTLDs (they have a standard zone file format so that the software used to parse on new gTLD will typically work on others), doing this on the .COM zone file is a bit more computer intensive and requires good design and planning. The uncompressed .COM zone file is approximately 8.9 GB of text data (the download itself is approximately 2.2GB). Most of the new gTLD zone files are under 15MB and can be processed relatively quickly.

Regards...jmcc

 

[accurate]

So that means that pending delete domains are not included in the zone files? That's how those lists are generated?

 

[katherine]

The zone files do not contain domain names that have no name servers. So that means that if such a domain was to expire and be deleted, this would not show up in the zone file. But there are not so many domain names with no name servers. In practice, if you compare two zone files on a daily basis (ie current release vs yesterday), you can see which domains were added (new regs generally), and which ones were removed (usually because they entered redemption status).

For the gTLDs, the registrar don't need the zone files to compute lists of deleting domains - they receive lists from the registries.

The zone file is just a snapshot of the domain names provisioned in the DNS.
This is not the registry database. The registry has its own backend that is a fully fledged database. The zone files do not contain whois info etc. Just the domain names, name servers and other DNS records like glue records or DNSSEC data.