How to modify "A" records on the slave when master is down?

Fr34k freaknetboy at
Thu Dec 4 00:12:00 UTC 2008


We leverage rsync: over scp (copy only those files changed automagically over SSH), perl, and cron.

Basically, a config DNS server super-master where you do all your changes and test them.
This super-master rsync's to several over DNS servers (say X servers) at various defined times.

cron and some perl later, you'll have X masters all up-to-date at those defined times - each of which is a copy of the super-master.
Rock solid secure setup with a test environment which is "one ring to rule them all".

Been doing it for years.

HTH -- Chris

----- Original Message ----
From: Mike Bernhardt <bernhardt at>
To: stevehunter_1 at; comp-protocols-dns-bind at
Sent: Wednesday, December 3, 2008 4:59:34 PM
Subject: RE: How to modify "A" records on the slave when master is down?

What we used to do is we had 2 masters. After an update was done on one of
them, we ran a perl script that would scp the db files to the other and then
send rndc reload to itself and the other master. That way both were always
up to date. It seems like if you had one master and one slave at each
datacenter, this would work very well. After the down datacenter comes back
up, simply run the script from the up-to-date master.

I can send you the perl script to save you some time if you want. The main
trick was getting scp to work with rsa keys so no password is required
(although it could work fine with a password if you're running the script


-----Original Message-----
From: stevehunter_1 at [mailto:stevehunter_1 at] 
Sent: Friday, November 21, 2008 9:10 PM
To: comp-protocols-dns-bind at
Subject: How to modify "A" records on the slave when master is down?

Hello.  I have two geographically different datacenters.  Each
datacenter has two instances of BIND.

There is one master out of these four.  The zones will have multiple
"A" records (pointing to the two datacenters to provide some minimal
amount of redundancy and load balancing)

What I want to do is put together a plan for when the master either
fails or the master becomes unavailable.

So if your master fails, or more likely, it becomes unavailable, and I
need to change the "A" records on the other slaves, how do you do it?

Can I have a master in each datacenter and a slave in each datacenter,
but a change made to any master propagates to all slaves?  For that
matter, can I just have four masters and be done with it?

It doesnt make sense that I could have multiple masters.. but I have
no idea how to solve this problem.  If datacenter A goes down for
three days, i want to be able to modify the slave "A" records to stop
pointing to the bad datacenter.  And when the datacenter comes back up
and the old master is alive, I want everything to work.

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