[libvirt-users] some problem with snapshot by libvirt

[xingxing gao]

thanks，i'll keep looking for it and share with others.

2012/5/30 Eric Blake <eblake at redhat.com>:
> On 05/29/2012 10:22 AM, xingxing gao wrote:
>> to create snapshot ,I did   step below:
>> virsh snapshot-create-as centos snap1 --disk-only --atomic --no-metadata
>> virsh snapshot-create-as centos snap2 --disk-only ......
>> ........................
>> virsh snapshot-creates-as centos snap10 .....
>> then i got 10 snapshot of a vm,
>> to revert, i just did the follow step:
>> 1 destroy centos
>> 2 editor="sed -i 's/centosdisk.snap10/centosdisk.snap1/g'" virsh edit centos
>> 3 rm -f centos.snap{2,3,4,5,6.....}
>
> Yes, that will be sufficient to revert to the state of the first disk
> snapshot, and on booting the 'centos' VM, your domain will have to run
> fsck in order to recover to the fact that the file system was not in a
> clean state at the time of the snapshot (basically, booting from your
> disk snapshot is the same as booting as if you had yanked the power cord).
>
>> 4 start centos
>> is these steps correct?
>> and another question is ,when i revert to a snapshot,some files of the
>> vm's system  missing，does this have any relation with the disk cache
>> mode (writeback,writethrough,none,etc.)???how could i avoid that
>> happen??
>
> You can install the qemu-ga guest agent in the guest, wire it up in the
> host XML describing that guest, and add the --quiesce option to your
> snapshot-create-as command in an effort to have the guest freeze file
> systems before taking the snapshot.  The end result will be that the
> file system is in a sane state (as if you had cleanly shut down), rather
> than in an incomplete state (as if you had yanked the power cord).
>
> I know that qemu-ga is available as part of the latest Fedora package,
> and that it was designed to be compiled for older Linux and also for
> Windows guests, although I don't personally have a good pointer for
> where to get the best version of qemu-ga for your specific guests.
> Maybe others can chime in here.
>
> --
> Eric Blake   eblake at redhat.com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>