zonfil

Zonfil, or zone file, is a DNS zone data file used by servers to map domain names to IP addresses and other data within a zone such as example.com. It is a plain text file loaded by DNS software and replicated to secondary servers through zone transfers.

A zone file consists of resource records. Each line specifies an owner name, an optional TTL, a class (IN for Internet), a type (A, AAAA, NS, MX, CNAME, TXT, SRV), and the RDATA. The file may begin with directives such as $TTL and $ORIGIN. Core records include SOA, NS, and data for hosts, mail, and services.

Common records: A and AAAA address mappings; NS delegations; MX mail exchangers; CNAME aliases; PTR records for reverse zones; TXT for text data, including SPF or DMARC. A simple example shows: $TTL 86400 ; @ IN SOA ns1.example.com. hostmaster.example.com. (2024062401 3600 900 604800 86400) ; NS ns1.example.com. ; @ IN A 192.0.2.1 ; www IN A 192.0.2.1 ; mail IN MX 10 mail.example.com.

Management and operation: zone files are read by DNS servers such as BIND or PowerDNS. Zone transfers (AXFR/IXFR) copy data to slaves. Dynamic updates (RFC 2136) allow changes without editing files. DNSSEC can sign a zone; DS records exist at the parent; RRSIG and DNSKEY entries are used in the zone. Validate zones with tools like named-checkzone, and manage serials and timestamps carefully. Security measures include restricting access, using TSIG for transfers, and keeping backups.

In practice, zonfil is a central piece of DNS administration, balancing static records and dynamic needs, and underpinning domain resolution in many networks.