NFS - DNS fail stops boot in mountlate
grarpamp at gmail.com
Fri Jan 7 03:53:55 UTC 2011
Yep, I gathered that. Is cool :)
> The canonical answer to this is to either mount them by IP, or
> to put the appropriate name in /etc/hosts. Depending on DNS for
> NFS mounts is not recommended.
That is the only available answer at the moment, but perhaps not
the best. And it's use case. Scalable systems require the flexibility
of name resolution. Secure environments (which you may be alluding
to) may already make use of secure/private DNS, hardcoding, keying,
etc. The DNS server may also be the NFS server for which backgrounding
could be appropriate. Forced hardcoding of IP's may not be ideal.
Not to mention in split-horizon networks, etc. In this DNS down
case, enhancing mount_nfs would allow the admin three choices:
hosts+fqdn:, ip:, fqdn:
However, not enhancing it only allows two:
FreeBSD is flexible (or should be) :)
> I read these statements to mean "if -o bg is used, the system
> should not hang/stall/fail during the boot process". Dumping to
> /bin/sh on boot as a result of a DNS lookup failure violates those
> statements, IMHO.
Yep, that's what I was thinking. If the admin want's to play DNS
and network games, sure, let them. But at least come up to let them
do it :)
I try not to argue use cases as someone will always have a need for
the bizarre and it just wastes keystrokes :)
Also, afaik, once mounted, the kernel uses only the resolved IP
address thereafter. So that is also a 'safe', unchanged, semantic.
Not sure about it's unmount, df and mount -v semantics, hopefully
something sane. Haven't tried downing NFS or changing DNS lately
to see. It's probably ok though.
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