# Migrating a DNS Zone Between Name Servers: BIND and PowerDNS

> Migrating a DNS zone between name servers: exporting from BIND, AXFR transfer, importing into PowerDNS with pdnsutil, and switching NS records with no downtime.

## What a DNS zone is and when it gets migrated

A DNS zone is a file with the records for one domain: A, AAAA, MX, TXT, CNAME, NS. A zone gets migrated when you switch DNS hosting, move from BIND to PowerDNS, or consolidate several name servers into one.

Before migrating, export the current zone to a text format — this serves as a backup in case of an error and as the source for importing on the new server.

## Exporting a zone from BIND

Zone files in BIND are usually located in `/etc/bind/zones/` or `/var/named/`. Check and export the zone with the following command:

```
named-compilezone -f text -o example.com.zone example.com /etc/bind/zones/db.example.com
cat example.com.zone
```

If the zone is stored in a database (BIND with DLZ) or file access is restricted, export the zone via an AXFR request from a server that has transfer permission.

## Transferring a zone with AXFR between BIND servers

AXFR is a protocol for a full zone transfer between name servers. On the old server, allow the transfer for the new IP address in `named.conf`:

```
zone "example.com" {
    type master;
    file "/etc/bind/zones/db.example.com";
    allow-transfer { 203.0.113.10; };
};
```

On the new server, request the zone:

```
dig axfr example.com @203.0.113.5
```

Save the resulting output as a zone file and load it as a master zone on the new server.

## Importing a zone into PowerDNS

PowerDNS stores zones in a database (MySQL, PostgreSQL, or SQLite) rather than in text files. Import the zone with the `pdnsutil` utility:

```
pdnsutil create-zone example.com
pdnsutil load-zone example.com example.com.zone
pdnsutil rectify-zone example.com
```

The `rectify-zone` command is required for zones with DNSSEC or a large number of records — it recalculates the internal fields in the PowerDNS database.

## Verifying the zone before switching over

Compare the record counts and the content of key fields on the old and new server:

```
dig +short A example.com @old-ns
dig +short A example.com @new-ns
dig +short MX example.com @new-ns
```

Also check the zone's serial number (SOA) — it must be higher than on the old server, otherwise secondary name servers will refuse the update. The general approach to a zero-downtime transfer is covered in the article on [managing DNS during a migration](https://www.zevshost.net/en/kb/migratsia-dns-bez-prostoya/).

## How to avoid downtime when changing NS servers

Lower record TTLs to 300 seconds 24-48 hours before the transfer — this speeds up the propagation of changes. Keep the old name servers running for at least 72 hours after changing the NS records at the registrar: some resolvers cache old NS records longer than they should.

## Summary: DNS zone migration checklist

- Export the current zone to a text file as a backup.
- Transfer the zone via AXFR or a manual import into PowerDNS.
- Lower record TTLs 24-48 hours before switching over.
- Check the SOA serial number and the content of the A, MX, and TXT records.
- Keep the old name servers active for at least 72 hours after the switch.
- Keep a list of subdomains with separate delegation — those NS records get checked separately, and they are a common source of discrepancies after the transfer.

If something goes wrong after changing the NS records, the recovery procedure is covered in the [migration rollback plan](https://www.zevshost.net/en/kb/migratsia-plan-otkata/). After the full switch, verify the site with the general [post-migration checklist](https://www.zevshost.net/en/kb/migratsia-proverka-posle/).

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Source: https://www.zevshost.net/en/kb/migratsia-dns-zony-bind-powerdns/