How to access contents of directory underneath mounted volume?

Hello,

On a RHEL4 host, I have a mountpoint, /thing, with a SAN volume mounted
at this mountpoint.

The local volume that contains the mountpoint (i.e. the volume that is
mounted at /) is nearly full, and I'm suspecting it is because there are
files on the local volume in the /thing directory. Of course, I can't
get to the /thing directory by normal means (at least AFAIK), because
there is currently a volume mounted at that mountpoint.

Does anyone know if it possible to access (i.e. see and delete) the
files in the /thing directory without having to umount the SAN volume
that is mounted at /thing?

Thanks,
Guy.
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Re: How to access contents of directory underneath mounted volume?

Guy Waugh wrote:

> On a RHEL4 host, I have a mountpoint, /thing, with a SAN volume mounted
> at this mountpoint.
>
> The local volume that contains the mountpoint (i.e. the volume that is
> mounted at /) is nearly full, and I'm suspecting it is because there are
> files on the local volume in the /thing directory. Of course, I can't
> get to the /thing directory by normal means (at least AFAIK), because
> there is currently a volume mounted at that mountpoint.
>
> Does anyone know if it possible to access (i.e. see and delete) the
> files in the /thing directory without having to umount the SAN volume
> that is mounted at /thing?

If some existing process has its CWD underneath /thing, then you can
access that directory via /proc//cwd.

You could use debugfs on the root fs, but I wouldn't recommend trying
to modify a filesystem while it's mounted r/w.

If you can't unmount the SAN because it's busy, you may still be able
to move its mount point with "mount --move". If you can allow for it
being unavailable briefly you could move it off just long enough to
rename the underlying directory, e.g.:

mkdir /thing.tmp
mount --move /thing /thing.tmp
mv /thing /thing.orig
mkdir /thing
mount --move /thing.tmp /thing
rmdir /thing.tmp

--
Glynn Clements
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Re: How to access contents of directory underneath mounted volume?

Glynn Clements wrote:
> Guy Waugh wrote:
>
>> On a RHEL4 host, I have a mountpoint, /thing, with a SAN volume mounted
>> at this mountpoint.
>>
>> The local volume that contains the mountpoint (i.e. the volume that is
>> mounted at /) is nearly full, and I'm suspecting it is because there are
>> files on the local volume in the /thing directory. Of course, I can't
>> get to the /thing directory by normal means (at least AFAIK), because
>> there is currently a volume mounted at that mountpoint.
>>
>> Does anyone know if it possible to access (i.e. see and delete) the
>> files in the /thing directory without having to umount the SAN volume
>> that is mounted at /thing?
>
> If some existing process has its CWD underneath /thing, then you can
> access that directory via /proc//cwd.
>
> You could use debugfs on the root fs, but I wouldn't recommend trying
> to modify a filesystem while it's mounted r/w.
>
> If you can't unmount the SAN because it's busy, you may still be able
> to move its mount point with "mount --move". If you can allow for it
> being unavailable briefly you could move it off just long enough to
> rename the underlying directory, e.g.:
>
> mkdir /thing.tmp
> mount --move /thing /thing.tmp
> mv /thing /thing.orig
> mkdir /thing
> mount --move /thing.tmp /thing
> rmdir /thing.tmp

Thanks Glynn, the last suggestion using "mount --move" looks like the
most useful. However, it's sounding like it's going to be easiest for me
to schedule some downtime.

Cheers,
Guy.
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