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Re: [Qemu-discuss] Issue with fsfreeze with qemu agent.

From: Dominique Ramaekers
Subject: Re: [Qemu-discuss] Issue with fsfreeze with qemu agent.
Date: Mon, 30 May 2016 13:25:40 +0000

Ok, that seems to be it.


I’ve got the ‘/’ and ‘/home’ on the same device formatted as btrfs on two separate sub volumes.


Is there a workaround to deal with btrfs?


Van: Christian Theune [mailto:address@hidden
Verzonden: maandag 30 mei 2016 14:05
Aan: Dominique Ramaekers
CC: address@hidden
Onderwerp: Re: [Qemu-discuss] Issue with fsfreeze with qemu agent.




I have encountered this before. Some operating systems may have bind-mounts that let a device appear multiple times in the mount list. Unfortunately the guest agent is not smart enough to consider a device that has been frozen as succesfull and keep going. This causes this specific error.


To verify this scenario, have a look at your list of mounts and see whether the same device appears multiple times, or whether other suspicious bind mounts appear.




On 30 May 2016, at 09:31, Dominique Ramaekers <address@hidden> wrote:



I use external snapshots to backup my guests. I use the 'quiesce' option to flush and frees the guest file system with the qemu guest agent.

With the exeption of one guest, this procedure works fine. On the 'unwilling' guest, I get this error message:
"ERROR 2016-05-25 00:51:19 | T25-bakVMSCmsrvVH2 | fout: internal error: unable to execute QEMU agent command 'guest-fsfreeze-freeze': failed to freeze /: Device or resource busy"

I don't think this is not some sort of time-out error, because activation of the fsfreeze and the error message happen immediately after each other:

$ grep qemu-ga syslog.1
May 25 00:51:19 CmsrvMTA qemu-ga: info: guest-fsfreeze called

This is the only entry of the qemu guest agent in syslog.

The difference of this guest in compresence with other, is that this guest runs postfix + amavis + spammassasin + clamav

Any help would be appreciated.

More info:

$ sudo virsh version
Compiled against library: libvirt 1.3.1
Using library: libvirt 1.3.1
Gebruikte API: QEMU 1.3.1
Draaiende hypervisor: QEMU 2.5.0

$ virsh qemu-agent-command CmsrvMTA '{"execute": "guest-info"}'
{"return":{"version":"2.5.0", ... ,{"enabled":true,"name":"guest-fstrim","success-response":true},{"enabled":true,"name":"guest-fsfreeze-thaw","success-response":true},{"enabled":true,"name":"guest-fsfreeze-status","success-response":true},{"enabled":true,"name":"guest-fsfreeze-freeze-list","success-response":true},{"enabled":true,"name":"guest-fsfreeze-freeze","success-response":true}, ... }

For making an external snapshot, I use this command:
$ virsh snapshot-create-as --domain CmsrvMTA sn1 --disk-only --atomic --quiesce --no-metadata --diskspec vda,file=/srv/poolVMS/CmsrvMTA.sn1




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