# In use but fuser finds nothing

## at

I have /usr on a separate partition and am running a system with grsecurity.

Each time the system is shutdown, I get the following error message:

```
 *   Unmounting /usr ...

 *   in use but fuser finds nothing        [ !! ]
```

And then once the system is started up, the filesystem is corrupted.

I have a feeling that grsecurity might be hiding some processes using that partition from the shutdown process trying to unmount it. But I might be wrong, of course.

Is there anything I should look at?

Thank you!

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## mimosinnet

At,

I am running grsecurity and I have not seen this. Could you post your fstab and your grsec/pax kernel options?

Cheers!

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## Hu

What filesystem are you using for /usr?  I have seen systems need a journal replay after a situation like this, but there should not be actual data corruption.

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## at

I am using JFS.

/etc/fstab entry is:

```
/dev/sda5       /usr            jfs             nodev,async,errors=remount-ro     0 2
```

The error message I am getting implies that it is possible the a filesystem would be in use but fuser would not see what is using it. Under what circumstances could that happen?

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## Hu

That can happen if there is a kernel side reference held to it.  You might have some other filesystem mounted at /usr/foo for some foo or you could have a file on /usr that is bound to a loopback device.  There may be other ways to have kernel subsystems hold references to it.  Those are just the most common ones I have seen.

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## Ant P.

I get that message on ext4 without grsec just by forgetting to unmount sshfs before a shutdown. No corruption, but it'd be nice if I didn't have to see it (and the delays it causes) at all.

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## at

Well, I don't use any loopback devices or sshfs. I am also absolutely certain that nothing else is mounted under /usr.

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## Khumarahn

I keep getting the same error with /tmp; my relevant line in /etc/fstab:

```

tmpfs                                           /tmp                tmpfs       size=11G                0 0

```

I wouldn't bother about this, but sometimes kernel panics after unmounting root, and computer does not shutdown. May be, these are related?

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## Hu

Those are probably not related, but without the panic text and callstack, it is hard to be sure.

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## Khumarahn

This is what I get on my screen:

http://138.26.76.81/4u/kernel-crash-1.jpg

After unsuccessful shutdown (read - every time) boot bios (or UEFI) gives a message and makes me wait for 10 seconds (which makes boot process 1.5 times longer):

http://138.26.76.81/4u/bios-message.jpg

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