Subj : Re: ODD DNS behaviour on Pi ZERO W with Bullseye OS
To   : All
From : Richard Kettlewell
Date : Wed Nov 19 2025 18:03:47

The Natural Philosopher <tnp@invalid.invalid> writes:
> So no, I don't know what it is now using as a DNS client.
>
> Its very odd. I just did this...
>
> # dig vps.templar.co.uk
>
> ; <<>> DiG 9.16.50-Raspbian <<>> vps.templar.co.uk
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24512
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 1232
> ; COOKIE: 7f7ca1b95493f5c601000000691d9a18750f0123b174788b (good)
> ;; QUESTION SECTION:
> ;vps.templar.co.uk.		IN	A
>
> ;; ANSWER SECTION:
> vps.templar.co.uk.	3726	IN	A	185.113.128.151
>
> ;; Query time: 9 msec
> ;; SERVER: 192.168.0.101#53(192.168.0.101)
> ;; WHEN: Wed Nov 19 10:21:12 GMT 2025
> ;; MSG SIZE  rcvd: 90
> ...then this...
> root@heating-controller:/var/ramlog# echo "This is  more  bollox isn't
> it?" | mail  -a "From: oil-monitor@heating-controller" -s "another
> message"  superroot@templar.co.uk
> ...and this...
> root@heating-controller:/var/ramlog# mailq
> -Queue ID-  --Size-- ----Arrival Time---- -Sender/Recipient-------
> C459D1FE2E      387 Wed Nov 19 10:21:48  oil-monitor@heating-controller
> (Host or domain name not found. Name service error for
> name=vps.templar.co.uk type=MX: Host not found, try again)
>                                          superroot@templar.co.uk
>
> -- 0 Kbytes in 1 Request.
>
> Now unless dig is using some other means than postfix to look up DNS,
> it looks like the problem is in postfix somehow.

Maybe, but the above doesn?t prove it; you?ve asked for an A record but
Postfix asks for an MX record, so your lookup won?t have populated the
cache (if there is one). (It?ll look for the A record next, but until
it?s got the MX record it doesn?t know what A record to ask for.)

If there is doubt about what name server is being used you could use
tcpdump to find out.

sudo tcpdump -np -i br0 udp port 53

Replace br0 with your own network interface. You?ll need to check at
least loopback (lo) and any real network interfaces.

-- 
https://www.greenend.org.uk/rjk/

--- PyGate Linux v1.5
 * Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

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