DragonFly BSD
DragonFly kernel List (threaded) for 2004-04
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Re: boot-time nfs mount issues should be fixed now

From: David Rhodus <drhodus@xxxxxxxxxxx>
Date: Tue, 13 Apr 2004 20:33:45 -0400

On Apr 13, 2004, at 6:03 PM, Matthew Dillon wrote:

The symptoms are NFS mount failures reported on the console, but the
NFS mount working just fine when executed manually after booting as

It turns out that the DNS resolver coupled with the use of short-form
names in /etc/fstab was to blame for this. e.g. leaf has this:

crater:/usr/src /usr/src        nfs     ro,bg           0       0
apollo:/FreeBSD /FreeBSD        nfs     ro,bg           0       0

And sometimes /FreeBSD would not mount during booting. It turns out
that the network is sometimes not fully operational when the RCNG
script gets to the NFS mounts and this causes the DNS resolver to fail.

Normally one would expect the resolver to retry a few times and obtain
a successful lookup. However, when a shortform name like 'crater' is
used the resolver winds up trying two hostnames 'crater.dragonflybsd.org.'
and 'crater.'. If the first lookup times out, but the second one does
not, the resolver returns the 'definitive' host-not-found error from
the second lookup when it really should return a try-again error from
the first lookup. The result is that the NFS mount fails because it
thinks that it was given definitely a non-existant hostname.

This problem can also cause weird failures to occur when the network
is sporatic or the name servers you are using get overloaded.

    In anycase, I just committed a fix to the resolver (which hopefully
    won't break anything else).

Thanks, thats been a pain for a very long time.


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