force DDNS update

[Simon Hobson]

Jason Gerdes wrote:

>I have been lurking here for a while with a similar issue.  I have 
>some 'stale' or nonexistent ddns records with the same setup.  Is 
>there a way to clear out all of the old mappings and just start 
>fresh, so to speak.  I have some network scripts that rely on the 
>hostname to be correct and this problem is wreaking havok on those 
>processes.  I have been receiving this error message in my logs that 
>I think might possibly help with the diagnosis:
>
>update failed: 'name not in use' prerequisite not satisfied (YXDOMAIN)

Yes, simply delete the stale records using nsupdate*

Thw DHCP server will NOT replace or remove an A record that does not 
have the correct TXT record to go with it. The TXT record has a hash 
of several bits of information that allows the server to determine 
that it wasn't something else that put the record there. This is a 
safety feature - otherwise someone could name their client "server" 
and the DHCP server would happily replace the A record for you 
important server of the same name with one that points to the client, 
with the obvious effects on the network !

Normally, the DHCP server will add the DNS records and at the same 
time add the information to the leases database. Similarly, the 
server will remove the two sets of information together (typically 
when a lease expires or is released by the client). For various 
reasons it's possible for the two to get out of sync and then you 
will have to manually fix it.

* You must use nsupdate to edit the zone 'live'. Alternatively, you 
can either freeze the zone ("rndc freeze somedomain.com" for Bind) or 
stop the dns server, edit the zone file, then unfreeze the zone (rndc 
unfreeze somedomain.com)/start the server.