Delete/update MX record

[Tony Finch]

@lbutlr <kremels at kreme.com> wrote:

> Using nsupdate when I try to delete an MX record for a domain, I get
> REFSUED.
>
> When I try to add an MX record with the same priority (or not), it
> leaves the old record as well.
>
> How do I remove and replace the MX record for a domain with nsupdate?

The UPDATE protocol will not tell the client why it didn't work; for that
you must check `named`s logs.

In general, with UPDATE it's best to delete then add records for a name,
using a single UPDATE transaction to avoid any point in time where the
name is missing. The comments in nsdiff say:

# For each owner name prepare deletion commands followed by addition
# commands. This ensures TTL adjustments and CNAME/other replacements
# are handled correctly. Ensure each owner's changes are not split below.

There's are a couple of cases where this doesn't work: the SOA and NS
RRsets. For SOA, you can just add the new record which implicitly replaces
the old one. For NS records, in my experience complete replacement is rare
enough that it's OK to simply nspatch the zone twice. (The NS delete will
be ignored instead of rejected.)

-- 
Tony Finch  <fanf at isc.org>  (he/they)  Cambridge, England
Shetland Isles: Variable 3 or less, becoming north or northeast 3 or 4
later. Slight, but smooth in southeast. Mainly fair. Good.