2000-12-29 18:03:05

by Frank.Olsen

[permalink] [raw]
Subject: Bugs in knfsd -- Problem re-exporting an NFS share

Hi -- could you please CC me if you reply to this mail.

My problem is that I get an error when setting up the following
configuration:

A: /exports/A - Redhat 7.0
B1/B2: mount /exports/A on /export/A from A - Redhat 6.2
C: mount /exports/A on /mnt/A from B1 or B2 - Redhat 6.2

I use knfsd/nfs-utils on each machine.

bash# ls /mnt/A
/mnt/A/A.txt: No such file or directory


I searched for a while on deja.com, and there seemed to be some indications
that knfsd was bugged and that using the user-mode code would work.
However, no one replied specifically to my message, so I'm still not sure.

BTW, what I tried to do was to set up a HA configuration of machines B1/B2
using A as a "shared disk".
This is just to try out the HA software without buying more hardware.

Thanks in advance for any help!

Best regards,
Frank Olsen

PS Happy new year!



2000-12-29 22:02:48

by NeilBrown

[permalink] [raw]
Subject: Re: Bugs in knfsd -- Problem re-exporting an NFS share

On Friday December 29, [email protected] wrote:
> Hi -- could you please CC me if you reply to this mail.
>
> My problem is that I get an error when setting up the following
> configuration:
>
> A: /exports/A - Redhat 7.0
> B1/B2: mount /exports/A on /export/A from A - Redhat 6.2
> C: mount /exports/A on /mnt/A from B1 or B2 - Redhat 6.2
>
> I use knfsd/nfs-utils on each machine.
>
> bash# ls /mnt/A
> /mnt/A/A.txt: No such file or directory
>

This is not a supported configuration. You cannot export NFS mounted
filesystems with NFS. The protocol does not cope, and it
implementation doesn't even try.
NFS is for export local filesystems only.

>
> I searched for a while on deja.com, and there seemed to be some indications
> that knfsd was bugged and that using the user-mode code would work.
> However, no one replied specifically to my message, so I'm still not sure.
>
> BTW, what I tried to do was to set up a HA configuration of machines B1/B2
> using A as a "shared disk".
> This is just to try out the HA software without buying more
> hardware.

Try "nbd" the network block device. That should be able to give a
more realistic imitation of a share disk.

NeilBrown


>
> Thanks in advance for any help!
>
> Best regards,
> Frank Olsen
>
> PS Happy new year!
>
>
> -
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> Please read the FAQ at http://www.tux.org/lkml/

2000-12-30 21:15:17

by Andrzej Krzysztofowicz

[permalink] [raw]
Subject: Re: Bugs in knfsd -- Problem re-exporting an NFS share


> On Friday December 29, [email protected] wrote:
> > Hi -- could you please CC me if you reply to this mail.
> >
> > A: /exports/A - Redhat 7.0
> > B1/B2: mount /exports/A on /export/A from A - Redhat 6.2
> > C: mount /exports/A on /mnt/A from B1 or B2 - Redhat 6.2
> >
> > I use knfsd/nfs-utils on each machine.
> >
> > bash# ls /mnt/A
> > /mnt/A/A.txt: No such file or directory
>
> This is not a supported configuration. You cannot export NFS mounted
> filesystems with NFS. The protocol does not cope, and it
> implementation doesn't even try.
> NFS is for export local filesystems only.

As I understand problem is somewhere else.
If this is intentionally unsupported configuration - OK. So why the error
appears ? The directory should be empty then.

If the configuration is unsupported at the moment and the A.txt file is
located on A, some code that attempts to read re-exported files/directories
should be turned off (eg. #if 0).

If the A.txt file is local for B1/B2 hosts, it is (IMHO) an obvious bug.
Sucgh a file should be hidden at the act of mounting. For both local and
remote access.

Neil, could you tell us where the A.txt file is *really* located ?

Regards
Andrzej

BTW. AFAIR, I observed similar behaviour (files are visible but
inaccessible) while mounting a local filesystem at a busy directory
(eg.: mount /dev/fd0 .;ls -l) even in 2.2...

--
=======================================================================
Andrzej M. Krzysztofowicz [email protected]
phone (48)(58) 347 14 61
Faculty of Applied Phys. & Math., Technical University of Gdansk