nfs bug & df: Can I lock up my kernel and overflow this buffer?
Jonathan Noack
noackjr at alumni.rice.edu
Mon May 9 23:21:08 PDT 2005
On 05/10/05 00:21, Billy Newsom wrote:
> Jonathan Noack wrote:
> > On 05/09/05 23:14, Billy Newsom wrote:
> > From the fstab(5) man page:
> > "The fourth field, (fs_mntops), describes the mount options associated
> > with the file system. It is formatted as a comma separated list of
> > options. It contains at least the type of mount (see fs_type below)
> > plus any additional options appropriate to the file system type. See
> > the options flag (-o) in the mount(8) page and the file system specific
> > page, such as mount_nfs(8), for additional options that may be
> specified."
>
> That is how I read the man page, too, long ago. But when I tried the -o
> option on the commandline, I was unable to send mount all of the
> mount_nfs commandline switches I needed. I either misunderstand the
> mount -o option, or it doesn't work for all of the mount_nfs stuff I
> tried to send it.
>
> In other words, the -o option seems to not like any of the many switches
> understood by mount_nfs .... hence I seemed to be forced to use
> mount_nfs directly. And that precludes using it in fstab.
You are not restricted to only the -o option with fstab. The native
mount_nfs switches work fine with it. This is stated in the second half
of the last sentence I quoted above (note the "and"). Thus, the same
options you use on the command line work with fstab.
> > What trouble did you have with fstab? You can specify as many options
> > as you want as long as you separate them with commas (I think putting a
> > '=' between an option and its value is also necessary, although I don't
> > know for sure). For you it should look like this (assuming you want
> > read/write):
> >
> > dell:/nfs /dellbak nfs rw,-s,-x=2,-T 0 0
>
> I don't know. Since mount wasn't able to understand those switches on
> the commandline, I never tried anything in fstab, for the sake of not
> causing any problems with my boot.
The handbook page on nfs has a few simple examples toward the bottom
(first hit on a Google search for "freebsd nfs fstab"):
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/network-nfs.html
To test the line I gave you just add it to /etc/fstab and see if "mount
/dellbak" works. It'll give you an error message if something is wrong.
For example, the options specified work perfectly for me and the mount
command completes successfully. Adding a "-z" to it gives an illegal
option error.
# grep shared /etc/fstab
server:/shared /mnt nfs rw,-s,-x=2,-T 0 0
# mount /mnt
# umount /mnt
<add "-z">
# grep shared /etc/fstab
server:/shared /mnt nfs rw,-s,-x=2,-T,-z 0 0
# mount /mnt
mount_nfs: illegal option -- z
usage: mount_nfs [-23bcdiLlNPsTU] [-a maxreadahead] [-D deadthresh]
[-g maxgroups] [-I readdirsize] [-o options] [-R retrycnt]
[-r readsize] [-t timeout] [-w writesize] [-x retrans]
rhost:path node
> 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
yourself?
--
Jonathan Noack | noackjr at alumni.rice.edu | OpenPGP: 0x991D8195
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