[libvirt-users] how to store an internal disk snapshot by use

xingxing gao itxx00 at gmail.com
Tue May 29 15:16:54 UTC 2012

as far as i kown ,we can use qemu-img command to do disk-only snapshot
while the vm is shut off

2012/5/29 Eric Blake <eblake at redhat.com>:
> On 05/29/2012 03:40 AM, Rujie Xu wrote:
>> Hello everyone,
>>     I am trying to find a way to store an internal disk snapshot and
>> supposed to restore later.
>>     Here is the problems I met:
>>     1) when I use SnapshotCreateXML() to create a disk_only snapshot while
>> the domain is inactive, there is an error happened:
>>      disk snapshot of inactive domains not implemented yet.
>>      I am wondering is there and way I can save the disk_only snapshot when
>> the domain is inactive right now?
> That code still has to be written.  It's on my todo list.
> https://bugzilla.redhat.com/show_bug.cgi?id=817226
> That said, if you _don't_ use the disk_only flag and the domain is
> offline, then the end result right now is that you get internal
> snapshots for free (since a system checkpoint of an offline domain _is_
> the disk snapshot, and since system checkpoint currently uses internal
> snapshots only).
>>      2) also use snapshotCreateXML() to create a disk_only snapshot while
>> the domain is active, and use the xml to set the <disk name="hda"
>> snapshot="internal"> there is also an error happened:
>>      unsupported configuration: active qemu domains require external disk
>> snapshot; disk hda requested internal
> Correct.  Qemu does not support the creation of internal disk snapshots
> except by the 'savevm' command which takes a system checkpoint snapshot
> (that is, unless qemu gives us a way to do disk-only internal snapshots
> of a running VM, you are stuck on this front).
>>      3) when I use snapshotCreateXML() to create a disk_only snapshot using
>> external file, it could be done, but when I try to use revertToSnapshot()
>> to revert this snapshot there is another error happened:
>>       revert to external snapshot not supported yet.
> Correct, that's another API that I haven't yet coded; and you're the
> second person to ask about it this week:
> https://www.redhat.com/archives/libvirt-users/2012-May/msg00122.html
>> Is there anyone can help me about this, or we just can't use libvirt to
>> managed the disk snapshot right now?
> Help in contributing code would be very welcome.
> --
> Eric Blake   eblake at redhat.com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
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