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at
Apprentice
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Joined: 20 Aug 2006
Posts: 185

PostPosted: Tue May 03, 2011 2:46 am    Post subject: In use but fuser finds nothing Reply with quote

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:
Code:
 *   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
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Joined: 10 Aug 2006
Posts: 686
Location: Barcelona, Spain

PostPosted: Tue May 03, 2011 4:50 am    Post subject: Reply with quote

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
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Joined: 06 Mar 2007
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PostPosted: Wed May 04, 2011 1:54 am    Post subject: Reply with quote

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
Apprentice
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PostPosted: Wed May 04, 2011 2:49 am    Post subject: Reply with quote

I am using JFS.

/etc/fstab entry is:
Code:
/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
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PostPosted: Wed May 04, 2011 3:37 am    Post subject: Reply with quote

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.
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PostPosted: Wed May 04, 2011 5:19 pm    Post subject: Reply with quote

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
Apprentice
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PostPosted: Wed May 04, 2011 8:39 pm    Post subject: Reply with quote

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
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PostPosted: Tue Feb 07, 2012 5:49 am    Post subject: Reply with quote

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

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
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PostPosted: Wed Feb 08, 2012 3:49 am    Post subject: Reply with quote

Those are probably not related, but without the panic text and callstack, it is hard to be sure.
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Khumarahn
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PostPosted: Wed Feb 08, 2012 5:29 am    Post subject: Reply with quote

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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