[CentOS] NFS / DNS problem

[Simone Mangelio]

Hi Andreas,

All the servers have the same /etc/resolv.conf file:

search our.domain.com
options ndots:2
nameserver ns0IP
nameserver ns1IP

I can't see any errors on the web servers or nfs servers referring a host
lookup failure.

Thanks

Simone


On 8/15/07, Andreas Rogge <arogge at gmx.de> wrote:
>
> Hi Simone,
>
> what nameservers are configured for the nfs-servers?
>
> Afaict the nfs-server does forward and reverse lookup the clients. So if
> your nfs-server's DNS breaks (i.e. if only ns0 is configured there and
> you shut down ns0) you might see the issue you described.
>
> Regards,
> Andreas
>
> Simone schrieb:
> > 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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