libvirt users - Dec 2014 - Re: Freeze Windows Guests For Consistent Storage Snapshots

Hi,
Is it possible to freeze windows guests for a consistent storage level
snapshot.
I am using openstack icehouse on centos 6.6
Hypervisor: KVM
Libvirt: 0.10.2
Qemu: 0.10.2

Guest OS: Windows 7 and Windows Server 2008

I was able to freeze Centos guests by issuing the  command:
virsh qemu-agent-command <guest_ID>
'{"execute":"guest-fsfreeze-freeze"}'

For CentOS guests, I enabled access between compute nodes and guests
through a socket by setting metadata parameter, hw_qemu_guest_agent=yes for
the guest image.
And then installing qemu-guest-agent inside the guest.

What steps do i have to follow for windows ?

Regars,
Payes

On 12/10/2014 11:40 PM, Payes Anand wrote:
> Hi,
> Is it possible to freeze windows guests for a consistent storage level
> snapshot.
Yes, if you install qemu-guest-agent in the guest, and wire up your
libvirt XML to have the guest-agent channel available.  Once you have
done that, use the --quiesce flag as part of creating your snapshots.
> I was able to freeze Centos guests by issuing the  command:
> virsh qemu-agent-command <guest_ID>
'{"execute":"guest-fsfreeze-freeze"}'
That is an unsupported backdoor, because it relies on libvirt-qemu.so.
You should really prefer the libvirt commands from libvirt.so instead
(the --quiesce flag to 'virsh snapshot-create[-as]'), because it is less
likely to get libvirt out of sync by going behind libvirt's back.  Also,
libvirt 1.2.5 introduced 'virsh domfsfreeze' as the official way to do a
guest-agent 'guest'fsfreeze-freeze' command, although since you are
using older CentOS builds, your libvirt does not yet have that command
supported.
> 
> For CentOS guests, I enabled access between compute nodes and guests
> through a socket by setting metadata parameter, hw_qemu_guest_agent=yes for
> the guest image.
> And then installing qemu-guest-agent inside the guest.
> 
> What steps do i have to follow for windows ?
The same steps - qemu-guest-agent is available for both Linux and
Windows guests.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

Eric Blake <eblake@...> writes:
> 
> On 12/10/2014 11:40 PM, Payes Anand wrote:
> > Hi,
> > Is it possible to freeze windows guests for a consistent storage level
> > snapshot.
> 
> Yes, if you install qemu-guest-agent in the guest, and wire up your
> libvirt XML to have the guest-agent channel available.  Once you have
> done that, use the --quiesce flag as part of creating your snapshots.
> 
> > I was able to freeze Centos guests by issuing the  command:
> > virsh qemu-agent-command <guest_ID>
'{"execute":"guest-fsfreeze-freeze"}'
> 
> That is an unsupported backdoor, because it relies on libvirt-qemu.so.
> You should really prefer the libvirt commands from libvirt.so instead
> (the --quiesce flag to 'virsh snapshot-create[-as]'), because it is
less
> likely to get libvirt out of sync by going behind libvirt's back. 
Also,
> libvirt 1.2.5 introduced 'virsh domfsfreeze' as the official way to
do a
> guest-agent 'guest'fsfreeze-freeze' command, although since you
are
> using older CentOS builds, your libvirt does not yet have that command
> supported.
> 
> > 
> > For CentOS guests, I enabled access between compute nodes and guests
> > through a socket by setting metadata parameter,
hw_qemu_guest_agent=yes for
> > the guest image.
> > And then installing qemu-guest-agent inside the guest.
> > 
> > What steps do i have to follow for windows ?
> 
> The same steps - qemu-guest-agent is available for both Linux and
> Windows guests.
> 
I installed the qemu-guest-agent on windows but when i run --
virsh qemu-agent-command <guest_ID>
'{"execute":"guest-fsfreeze-freeze"}'
from my host machine, the guest windows VM doesn't freezing.
Although the command returned successfully. value returned was 2.
Is it possible to freeze NTFS filesystem using the above command ??
I had downloaded guest agent for windows from here--
https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/
Am I missing something ??