[ovirt-users] Pre-snapshot scripts to run before live snapshot

[Yaniv Kaul]

On Thu, Mar 8, 2018 at 12:47 AM, Gianluca Cecchi <gianluca.cecchi at gmail.com>
wrote:

> On Tue, Mar 6, 2018 at 7:54 PM, Yaniv Kaul <ykaul at redhat.com> wrote:
>
>>
>>
>> On Mar 6, 2018 7:02 PM, "Gianluca Cecchi" <gianluca.cecchi at gmail.com>
>> wrote:
>>
>> Hello,
>> this thread last year (started by me... ;-) was very useful in different
>> aspects involved
>>
>> http://lists.ovirt.org/pipermail/users/2017-March/080322.html
>>
>> We did cover memory save or not and fsfreeze automatically done by guest
>> agent if installed inside the VM.
>> What about pre-snapshot scripts/operations to run inside guest, to have
>> application consistency?
>> Eg if I have a database inside the VM and I have scripted my backup job
>> involving live-snapshot (eg with the backup.py utility of the thread)
>>
>>
>> https://github.com/guillon/qemu-plugins/blob/master/scripts/
>> qemu-guest-agent/fsfreeze-hook.d/mysql-flush.sh.sample
>>
>>
>>
> Hello Yaniv,
> thanks for the information and the example file link.
> So I have understood that the freeze-hook script is run with the "freeze"
> option before snapshot and again but with the "thaw" option after the
> snapshot.
> So I can manage what to do, parsing the argument given
> So far so good.
> I have tested with a Fedora 27 guest and all is ok there.
>
> Now I would like to do something similar for a Windows 2008 R2 x64 VM.
>

Windows is somewhat different. In fact, it's a bit better than Linux (ARGH!
but it's true) with its support for VSS - an API for applications to
register to events such as backup.
You should have the QEMU guest agent VSS provider installed (Note: need to
see where's the latest bits - I found[1]).

Then, if your application supports VSS, you are all good (I believe).
Y.

[1]
https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/archive-qemu-ga/qemu-ga-win-7.4.5-1/

I see that the qemu-guest-agent has been installed under
> C:\Programs\qemu-ga and that the "QEMU Guest Agent" service is run as
> "C:\Program Files\qemu-ga\qemu-ga.exe" -d
>
> In fact I see I have a registry key in
>
> HKLM\SYSTEM\CurrentControlSet\services\QEMU-GA
>
> with the same value above for ImagePath ;
> "C:\Program Files\qemu-ga\qemu-ga.exe" -d
>
> What should I do to enable a freeze-hook script on Windows now?
>
> BTW: searching around while trying to understand more, I found that:
>
> on hypervisor running the VM I have
>
> # vdsClient -s 0 getVmStats vm_guid
>
> that works and gives me information that confirms agent seems to
> communicate and I get also
> appsList = [.... , 'QEMU guest agent', ...]
>
> Also, the dump of the dynamic xml for the guest contains
>
> # virsh -r dumpxml VM_NAME
>
>     <channel type='unix'>
>       <source mode='bind' path='/var/lib/libvirt/qemu/
> channels/420e5014-9b26-a4c0-9d79-ed9b123304de.org.qemu.guest_agent.0'/>
>       <target type='virtio' name='org.qemu.guest_agent.0'
> state='connected'/>
>       <alias name='channel1'/>
>       <address type='virtio-serial' controller='0' bus='0' port='2'/>
>     </channel>
>
> I tried to get its settings from qemu guest agent using socat and unix
> domain sockets but I don't receive answer
>
> # socat unix-connect:/var/lib/libvirt/qemu/channels/420e5014-9b26-
> a4c0-9d79-ed9b123304de.org.qemu.guest_agent.0 readline
>
> and then in the interactive prompt
>
> {"execute":"guest-info"}
>
> to get and verify information about fsfreeze, something like
> ...., {"enabled": true, "name": "guest-fsfreeze-freeze"}, ... ....,
> {"enabled": true, "name": "guest-fsfreeze-thaw"}, ...
>
> But I didn't get any line....
> Is this communication from OS disabled by design out of oVirt mgmt?
>
> Thanks again for any info to configure freeze-hook in Windows guest.
>
> Gianluca
>
>
>
>
>
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