[libvirt] Using Libvirt to change the bridge a virtual network card of a running vm is connected to

[Daniel P. Berrange]

On Fri, Jan 20, 2012 at 12:42:18PM -0500, Laine Stump wrote:
> On 01/20/2012 11:05 AM, Ralf Spenneberg wrote:
> >Hi there,
> >
> >we are using libvirt to manage our VMs. We have several VMs connected to
> >different bridges on the same physical KVM host. We need to change the
> >bridge a virtual machine is connected to once in a while. Currently we
> >are just using brctl to do that. Since this needs to be done over the
> >network we would like to use the Libvirtd. Currently this does not seem
> >possible. We have not found any interface or function within the libvirt
> >library to implement this in a live VM. Only shutdown VMs may be changed
> >via editing the XML representation.
> 
> One way to do this would be to detach the network device, then
> reattach it with the configuration changed. Of course this would
> result in the guest seeing its network device disappear, then
> re-appear again, which is probably not what you want (although it's
> still a bit better than shutting down the entire guest).

I think I've mentioned before that I'd like to see the

 virDomainUpdateDevice()

API enhanced, so that you can change the network device backend on
the fly without touching the guest device. It is probably already
possible todo given current QEMU functionality for adding/removing
host network backends - provided QEMU doesn't auto-kill the guest
device when you remove the host device.


Daniel
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