[ovirt-users] how to run command in windows guest via agent?

[Gianluca Cecchi]

On Thu, Mar 15, 2018 at 2:26 PM, Sergey Vavilov <sergey at vavilov.org> wrote:

> Hello!
>
> I'm wondering
> how can I run a cmd.exe command (or powershell) inside windows guest
> virtual machine by
> ovirt-agent from outside (from ovirt-engine or from host)?
> What's ovirt's analogue for
> virsh qemu-agent-command
> ?
> Actually, I want to setup ip on virtual NIC.
> So I can't run a command via windows' protocols.
> ovirt-agent service works in windows virtual machine and successfully
> reports its state to ovirt engine.
> But it looks like ovirt-agent isn't suitable to run commands in virtual
> machines?
> Or am I wrong?
> Should I configure a coexistence of ovirt-agent and qemu-agent inside vm
> somehow?
> How did you solve such task before?
>
> Thank you, all!
>
>
> --
> Sergey Vavilov
>
>
Hi Sergey,
I recently had a need for a Windows 2008 R2 x86_64 VM that I moved from
vSphere to RHV (but the considerations below are the same for oVirt).
In my case I had to run a backup of an Oracle database that is in
NOARCHIVELOG mode, due to performance reasons: it is an RDBMS used for BI
that is refreshed every day and doesn't need a point in time recovery but
only a consistent state before the "new day" processing is run at 01:00 in
the night.
In vSphere the backup of the VM was implemented with Veeam, that uses
snaphsot technology and interacts with VSS layer of M$ operating systems.
Oracle fully supports on Windows the backup of database using VSS only if
it is in ARCHIVELOG mode.
https://docs.oracle.com/cd/E11882_01/win.112/e10845/vss.htm#NTQRF475

Veeam automatically executed shutdown / snapshot / start of the dabatase
because I think it implements what in the link above is called as
PRE_SQLCMD in OnPrepareBackup callback (through the VeeamGuestHelper.exe
executable).

Coming back to oVirt, the interaction with Windows VSS layer is indeed done
by "QEMU guest agent"too; you have to install it together with the oVirt
Guest Agent when you install oVirt Guest Tools

So in my case I would need for Windows something similar to the
"fsfreeze/thaw hooks" I have in Linux QEMU guest agent.
But searching through the code it seems this functionality is only present
in Linux component...
In fact some days ago I wrote to the qemu-devel mailing list to ask for
possible implementation:
http://lists.nongnu.org/archive/html/qemu-devel/2018-03/msg02823.html

No answer so far. Feel free (you and others) to contribute to the thread if
you think it can help...
It could also be useful to have at least writer control commands
implementation in VSS interaction of QEMU Guest Agent in Windows, so that
one could do something similar to what Veeam on vSphere already does...

Based on what I have wrote above, I doubt you could interact at all through
the QEMU guest agent on Windows to run any command...
And also for Linux guests, I think you are restricted to the default
actions (eg shutdown) or forced to use as a workaround the approach to run
a snapshot (that then you delete) and "attach" the desired command to the
freeze (or thaw) hook...

HIH,
Gianluca
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