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Re: Random chmod errors

From: Peter Kratzer
Subject: Re: Random chmod errors
Date: Thu, 9 Jun 2005 10:44:59 +0200

> Peter Kratzer wrote:
> > some of my users are encountering random errors with the chmod command.
> > errors are not exactly reproducible, so I cannot even narrow down the
> > circumstances of their occurrance.
> Problems like that can be disheartening and hard to track down.  I saw
> James' question and your response that you were working on an NFS
> server.  I am not familiar with "NAS filer".  But if there is any
> ability to look at logs for errors there that would be good.  This may
> very well be a problem in the NFS between the systems.

Hi Bob,

thanks for your advice.

With "NAS filer" I am talking about a StorageTek Network Attached Storage
device, connected to the Linux machines by NFS.

I have checked the log files without success.

We have also contacted the StorageTek support. They don't have a clue
either. They suggested a network trace on the storage device. The problem
there is the trace stopa a file size of 1 GB. And that's nothing for lots
of users using the same machines and often producing hundreds of gigabytes
of hardware simulation data. As long as I cannot predicably reproduce the
problem I am lost there.

> > What else do I know:
> > - Following message occurs: "chmod: changing permissions of
> > `filename' (requested: 0644, actual: 0444): Operation not permitted"
> Seeing "operation not permitted" indicates to me that the filesystem
> (NFS server in this case?) refused the operation.  That is also the
> message you would get when trying to chown without the privilege.

That's right. But there are two differences to that case:
1. The error message would occur a second time trying the same command,
which it does not.
2. In my case the additional output in brackets is produced, which it does
not if I really do not have the privilege to access the file's permission.

> I have had enough problems with NFS in the past that now it is one of
> my "usual suspects" whether it is really the problem now or not.

I will focus on NFS.

> > - The message differs from attempting to chmod files owned by different
> > users in the following part: "(requested: 0644, actual: 0444)"
> > - I have tried to find this message part in brackets ("requested: 0644,
> > actual: 0444") in the chmod.c source, but without success
> This may have been introduced in a downstream patch to the GNU
> sources.  You could look at the RH distro source and see.
> I would build a pristine copy of latest coreutils.  I would run all of
> the make checks because maybe in the tests on your system it would
> turn up something.  I would place a copy of the pristine newly
> compiled chmod in /usr/local/bin so that it would shadow the distro
> supplied version for your users.  If the problem goes away and that is
> the only change then you know it is due to something in the code.  You
> should even be able to double-blind test it if you desired.
> Unfortunately if the problem remains you don't know anything more.

This is very helpful information. I will continue as you suggested.

Since I will not be in the office until monday I can start with this
procedure not before next week.

Thanks for your support so far.

With best regards,


>   ftp://ftp.gnu.org/gnu/coreutils/coreutils-5.2.1.tar.gz
>   ftp://ftp.gnu.org/gnu/coreutils/coreutils-5.2.1.tar.bz2
>   ftp://alpha.gnu.org/gnu/coreutils/coreutils-5.3.0.tar.gz
>   ftp://alpha.gnu.org/gnu/coreutils/coreutils-5.3.0.tar.bz2
> Bob

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