Arch Linux

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

LVM snapshots cause [FAIL] at 'Unmounting Filesystems'

I have LVs containing /, /var, /home, and swap. If I have any snapshots of any of these, the 'Unmounting Filesystems' step during down/restart fails. It doesn't seem to cause any corruption; what I noticed initially was that the /var partition always needs journal recovery on the next boot. If I boot to the Arch installer and run dumpe2fs on it, it always reports clean. If I then run fsck from the installer, the journal recovery occurs there, so there's no recovery during boot of the installed system.

The only thing I found in the logs is a rearrangement of the /dev/dm-# entries, but that doesn't seem strange considering how snappshotting works. Plus it doesn't seem to happen until after reboot. I have absolutely no idea where to go from here, so any suggestions would be appreciated. Thanks

Last edited by alphaniner (2011-08-03 19:49:41)

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But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner

stqn

Member

Registered: 2010-03-19

Posts: 1,191

Website

Re: LVM snapshots cause [FAIL] at 'Unmounting Filesystems'

I use snapshots to backup my root and often it will fail saying that the device is in use, even though my script first unmounts, then calls sync and sleep 2 before calling lvremove. A while later it will work.

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: LVM snapshots cause [FAIL] at 'Unmounting Filesystems'

I think your situation is very different from mine.  I have never mounted or otherwise read from the snapshots.  Just 'having them around' causes problems, even a snap of /home which is effectively idle (I made a user but I'm still logging in as root).

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But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: LVM snapshots cause [FAIL] at 'Unmounting Filesystems'

I've done some more poking about, but all I've come up with is the fact that this isn't an 'isolated incident'.  I originally saw the error on my home box with Arch 64-bit, but I duplicated it on a 32-bit VBox VM.  I have also tried both ext4 and reiser filesystems on /var, no difference.

Also, I forgot to mention before: once I get rid of the snapshot, the problems go away immediately. At the next down/restart the unmounting step does not fail, and there's no journal recovery at the next boot.

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But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: LVM snapshots cause [FAIL] at 'Unmounting Filesystems'

Per falconindy's suggestion on a potentially related thread, here's the output of ps aux and lsof from just before the unmount step in rc.shutdown:

No snapshot:
ps
lsof

With snapshot:
ps
lsof

I did some magic with the ps outputs and found these to be unique to the second case:

[ksnaphd]
[kcopyd]
[kworker/0:3]
/sbin/dmeventd

Last edited by alphaniner (2011-08-08 17:00:00)

---

But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner