[CentOS] NFS / DNS problem

[Peter (CentOS List)]

The first thing that popped in my head was reverse lookup, but as I kept
reading and saw your test with web3 it could ave been a sync problem
between the two nameservers. By restarting ns1 all the zones were synced
again and your initial problem isn't there anymore and so your test with
web3 was successful as in it didn't loose it's mount. Keep an eye on ns1
when you make updates in the zones on ns0. I have seen problems where
the sync didn't occur automatically and I had to sync "manually" by
stopping and starting bind on the secondary server.

Hope it helps you a little bit.

Peter

Simone wrote:
> Hi all,
> 
> Today we have had a strange problem that has taken down our website, we
> understand what happened but not why so I am hoping someone has seen
> this before.
> 
> We have our web servers (web1 web2 web3 ..... web10) mounting an NFS
> share (/export/data) from server nfs1. On the web server side we use
> autofs in the format nfs-dedicated:/export/data where nfs-dedicated is
> an alias in our internal DNS servers pointing to server nfs1. We run a
> primary and a secondary DNS (bind) server ns0, ns1 authoritative for our
> zones and our webservers have them configured in /etc/resolv.conf
> Today we had to run some upgrade on the dns servers (bios firmwares etc)
> so we took down ns0 and with it our website went down.
> All the nfs shares disappeared from the web servers (the logs show
> requests to mount/unmount timing out), but at the same time on nfs1 the
> logs show requests (mount and unmount) coming from the web servers and
> no errors.
> 
> As soon as ns0 is back up, all gets back to normal. Minutes later we
> take down ns1 for maintenance and it doesn't have any impact on the
> website.
> 
> dig @ns0 nfs-web gives exactly the same results on ns0/1
> 
> Back to the office we try to reproduce the same scenario configuring
> iptables on web3 to block traffic to ns0 but the server (web3) keeps
> working fine reverting to ns1 for name resolution (as you would expect).
> 
> Has anybody seen this happening before? Any comment/suggestion much
> appreciated.
> 
> Thanks
> 
> Simone
> 
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> 
> 


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