In message <20090202163756.5f8a6...@il130.idmt.fraunhofer.de>, Johannes Hirte
writes:
> Ok second try, since my first mail didn't reached the ML.
>
> I run into write problems with unionfs and nfs and found this thread on
> the ML:
>
> http://www.fsl.cs.sunysb.edu/pipermail/unionfs/2008-November/005949.html
>
> This describes pretty good my problem. I'm booting from network into an
> initrd, mounting a tmpfs (rw) and a nfs-export (ro) together with
> unionfs. The problem is, I can't modify a file from the nfs. Deleting
> or creating is no problem, only modifying ends in "Permission denied".
> I can do a chmod 600 on this files. Then this file can be modified. The
> behavior was reproducible with kernel 2.6.27.13 and 2.6.24.4 with
> unionfs-2.5.1. A 2.6.24.4 setup with unionfs 2.3.2. A solution would be
> really good cause this is a showstopper for updating this netboot
> environment.
>
> Johannes
Johannes, I've tried the procedure again today and was still unable to
reproduce it. I tried it with unionfs-2.5 and 2.5.1 on 2.6.27.10. I
followed your descriptions precisely as per the URL below (one nfs-ro
branch, set as ro in unionfs and copyup to a rw branch). In my case, strace
showed this for the "echo >test" command:
open("test", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3
Since you've tried many kernel version, I don't think it's the linux kernel.
1. What can you tell me about your NFS server? What OS and OS version is
it? What version of the NFS proto do you use (2? 3? 4?) and what
transport (udp? tcp)? I'll try to reproduce the conditions exactly on my
end.
2. Are your kernels pretty much vanilla or is there something special about
them like additional non-mainline patches applied that could affect
things (e.g., tomoyo, rt-linux, etc.). If your kernels differ, please
give me a tarball of your kernel sources and your .config.
3. I'd like to get your kernel .config to see if you turned on any other
options that could make a difference (esp. extra security stuff). Do you
use ACLs, SElinux, or the like? Those are the kinds of things that can
effect permission checking.
4. Any chance I can get a temp ssh access to a system you have that
demonstrates this? In my experience, a 5 minute poking around a system
can save everyone many hours/days of emails and attempts to second guess
each other.
BTW, if you haven't already, can you open a bugzilla report on this
(https://bugzilla.filesystems.org/), then upload logs and config files as
needed; others who've seen a similar issue can ask to be CC'ed on that
bugzilla report, so we don't have to innundate the ML with a barrage of "can
you try XYZ now" messages. :-)
Thanks,
Erez.
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