boot-time nfs mount issues should be fixed now

[David Rhodus]

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.

-DR