[Pdns-users] PDNS Server migration - Using AXFR to a Slave-Capable Backend

David opendak at shaw.ca
Thu Nov 16 14:25:31 UTC 2017

On 2017-11-16 2:07 AM, Mislav | SysAdmin wrote:
> Hi. I've the following setup:
> 1) pdns server version 3.1 - with mysql backend
> 2) pdns server version 4.1.0 - with mysql backend
> What I'm trying to do is:
> - replace version 3.1 with 4.1.0 and I've installed clean version of
> 4.1.0 to a new server and I'm trying to this this now:
> https://doc.powerdns.com/authoritative/migration.html#using-axfr-to-a-slave-capable-backend
> Although this is working fine, my zones are transfered, AXFR is working,
> I've a small problem/question related to that.
> Every time I add some domain, I always get 2-3 empty records, here is
> the zone example:
> 1) https://pastebin.com/LpnzKjwW - this is original master zone from 3.1.
> 2) https://pastebin.com/5uV2Lk5N - slave zone added on 4.1.0 and
> transfered using AXFR

These appear to be empty non-terminals, to provide non-NXDOMAIN for 
b.example.com if a.b.example.com exists.

If you added a record like a.b.c.d.e.f.g.h.i.j.k.example.com you would 
see a large amount of these.

I believe they are also required for doing DNSSEC properly too (NSEC 

> You will see that first zone has 23 records and when transferred, it has
> 25 records. Any idea why is there always something in
> the name, but type and content are always empty? It doesn't matter if
> master is pdns server 3.1, I've also tested it with one
> bind/named master server and in that scenario result was the same.
> Always 2-3 empty records in the zone. How to debug
> this in order to find out why are those getting created in the first
> place? Or how to fix this?
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