libvirt users - May 2012 - how to store an internal disk snapshot by use

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?

     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

     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.

Is there anyone can help me about this, or we just can't use libvirt to
managed the disk snapshot right now?

Thanks very much!
-- 
Best Regards,
Roger Xu
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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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