DragonFly BSD
DragonFly kernel List (threaded) for 2004-05
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Re: boot-time nfs mount issues should be fixed now


From: user@xxxxxxxxxxxxxx
Date: Fri, 14 May 2004 16:53:47 -0700

David Rhodus wrote:
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
    completed.

    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.

Also patched/MFCd in FreeBSD. Thanks.


-Nate

P.S. Feel free to cc me on bugfix patches that have a common origin in the future.



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