nfs bug & df: Can I lock up my kernel and overflow this buffer?
billy at nlcc.us
Tue May 10 15:16:22 PDT 2005
Jonathan Noack wrote:
>> Anyone tried that sort of stuff in fstab? I'm a little skeptical.
> I use "that sort of stuff" and have for a long time. Here's one of my
> fstab lines:
> optimator:/usr/home /usr/home nfs rw,-3,-T,-r=32768,-w=32768 0 0
> It's obvious you don't believe me but why are you unwilling to try it
Well, because this fails to work on the commandline:
#mount -o -s -x 2 -T dell:/nfs /dellbak
I tried tons of different ways, never could get mount to do that, so I
gave up on fstabbing options.
Since the above mount command wouldn't even work, I figured I could
forget about putting those same options (which mount calls illegal) in
the fstab file. That's where the man pages only go so far. Without the
examples you give, I was pretty sure that it was pointless to get fstab
options to do what mount wouldn't.
What it boils down to is that mount is fine with these options in fstab,
but barfs when doing them on the commandline. That was so
couter-intuitive, I went around it for the sake of getting things done.
FreeBSD man pages are nice and all, but without a textbook siting by
with some examples, it can be difficult. I learned Unix pretty much ad
hoc, so I find that examples (such as you gave) are worth much more than
man pages now that I know most of the basics.
But what I did discover is that if I mount the same nfs resource
multiple times, I get multiple, identical mounts (using fstab options,
or commandline, either one). I have to umount each one serially. How
is this a feature? What good does it do me if I mount the same nfs
drive to the same place n times? Won't that eventually cause a deadlock
as n increases beyond a few hundred or thousand? -- especially when the
NFS server goes down? Shouldn't the second and subsequent mounts either
fail or not be attempted due to a sanity check?
mount: /dev/ad0s1f: Device busy
That seems reasonable for /usr. But as I stated before, NFS resources
nevere apparently become "busy", and there is no sanity check to prevent
mulitiple simultaneous mounts of identical file systems on identical
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