another nsupdate question

[Kevin Darcy]

Charles Bodley wrote:

>      The examples below show how nsupdate could be used to insert and delete
>      resource records from the example.com zone.  Notice that the input in
>      each example contains a trailing blank line so that a group of commands
>      are sent as one dynamic update request to the master name server for
>      example.com.
>
>            # nsupdate
>            > update delete oldhost.example.com A
>            > update add newhost.example.com 86400 A 172.16.1.1
>            >
> Is there anyway to just update not remove then re-add? According to the man
> page it's sent as one request does this mean that if it fails nothing
> happens or can it fail in such away that there in no record left?

The only record type that can be atomically replaced is SOA. See the
infamously-unclear Section 3.4.2.2 of RFC 2136. You have to make sure, however,
that the SOA.SERIAL of the new record is higher (according to serial-number
arithmetic) than the SOA.SERIAL of the old record.

In nsupdate terms, just "update add" the new SOA record and it should replace
the old one.


- Kevin