A loop device mounted within an NFS share is not accessible via NFS?

srikanthnv · 11-23-2008, 11:52 PM

Folks, I have a strange problem and I hope someone will be able to help me out :-)

There is a directory, say /opt/nfs, exported over NFS. Within /opt/nfs there are a bunch of subdirectories, say dir1, dir2 etc.

Now, if I try to NFS mount dir1 directly using a command like

Code:

mount -t nfs localhost:/opt/nfs/dir1 mountpoint

it works flawlessly.

Now, I have an ext2 filesystem image that I need to mount on dir1. So I mount it using a loop device like so

Code:

mount -o loop fs_image /opt/nfs/dir1

and it works. But now, I am unable to access dir1 over NFS! So now when I try the same command as before

Code:

mount -t nfs localhost:/opt/nfs/dir1 mountpoint

I get this error

Code:

mount: localhost:/opt/nfs/dir1 failed, reason given by server: Permission denied

Any idea why this might be happening?

BTW, I'm doing ALL of this as root. (This is just to avoid any minor permissions issues due to ownership of files

)

kenneho · 11-24-2008, 03:11 AM

You could try and add the verbose option, maybe that will tell us something.

And what does "showmount -e" tell you?

srikanthnv · 11-24-2008, 03:54 AM

OK, adding the verbose option "-v" didn't give me any extra information. The man pages for mount tell me that verbose only prints messages when the mount succeeds.

showmount -e shows me that /opt/nfs is exported... The entry is, and I quote :-)

Code:

/opt/nfs                                                                                            *

kenneho · 11-24-2008, 03:59 AM

Hmmm...what kind of filesystem are you trying to mount? Could you add that explicitly to the mount command?

srikanthnv · 11-24-2008, 04:03 AM

fs_image is an ext2 filesystem. I added the "-t ext2" to that mount command. It didn't help :-(

billymayday · 11-24-2008, 04:16 AM

Can you mount one level higher (ie /opt/nfs)

If so, what happens if you navigate down to dir1?

srikanthnv · 11-24-2008, 05:12 AM

I can mount one level up, but when I navigate down to dir1 and hit ls, it's empty...

In case it helps I also noticed that the first time I tried to enter dir1 after the NFS mount, it took ages (around 30s) to step into that directory.

billymayday · 11-24-2008, 05:26 AM

Try restarting NFS on the server after you mount the iso

kenneho · 11-24-2008, 05:51 AM

And maybe mount with the "soft" option set, so that you'll get an error message instead of hanging.

srikanthnv · 11-25-2008, 12:56 AM

billymayday: That didn't work either :-( I still get the same error.

kenneho: The mount isn't hanging so adding the soft option (to the NFS mount) didn't make any difference :-(

billymayday · 11-25-2008, 01:21 AM

Problem for me is it works!

First I did it remotely, then realised you were trying it on localhost (I won't ask why).

What does your exports look like?

Here's the relevant line from mine

Code:

/mnt/iso        192.168.1.0/24(rw,sync) localhost(rw,sync)

What gete me is it mounts without the iso mounted.

What are the permissions of the iso?

srikanthnv · 11-25-2008, 01:35 AM

I think the difference between what you do and what I do is that I have "/mnt" exported (the top level directory). And within that I have mounted the loop device (in your case, i guess your ISO is mounted at /mnt/iso).

My /etc/exports file looks like this

Code:

/opt/nfs *(rw,no_root_squash,no_all_squash,sync)

If I export the /opt/nfs/dir1 directly, I am able to access it, but NOT when I try it this way.

I think I might be asking for too much, but can you try it by exporting the /mnt directory, mounting your ISO at /mnt/iso, then trying to NFS mount the /mnt/iso? If that works for you, then I'm definitely screwing up something :-)

Edit: I set the /etc/exports the same as yours, and restarted the NFS server. That didn't work. And BTW my fs_image file's permissions are set to 777.

billymayday · 11-25-2008, 01:54 AM

Will do, but tied up for a while

billymayday · 11-25-2008, 02:07 AM

No, it doesn't work if I take /mnt/iso out of exports.

srikanthnv · 11-25-2008, 02:10 AM

Thanks a bunch for checking! BTW, do you get the same "permission denied" error?