[ovs-discuss] Problem with OpenVswitch 1.0.0 database backend and persistent settings.

Dan Wendlandt dan at nicira.com
Fri May 21 20:02:16 UTC 2010


On Thu, May 20, 2010 at 1:47 AM, Mark Persohn <
Mark.Persohn at superchoice.com.au> wrote:

>
> I have looked at trying to run a script as prt of the VM startup but since
> we are running libvirtd/qemu in bridge
> mode it will not run scripts!


I do not have any hands-on experience with libvirt and KVM, but from talking
to other people who have used OVS with libvirt, I was under the impression
that libvirt provides a mechanism by which you can bring up VM interface
devices using an arbitrary script.

The libvirt docs (http://libvirt.org/formatdomain.html#elementsNICSEthernet )
mention:

Generic ethernet connection

Provides a means for the administrator to execute an arbitrary script to
connect the guest's network to the LAN. The guest will have a tun device
created with a name of vnetN, which can also be overridden with the <target>
element. After creating the tun device a shell script will be run which is
expected to do whatever host network integration is required. By default
this script is called /etc/qemu-ifup but can be overridden.


  ...
  <devices>
    <interface type='ethernet'/>
    ...
    <interface type='ethernet'>
      <target dev='vnet7'/>
      <script path='/etc/qemu-ifup-mynet'/>

    </interface>
  </devices>
  ...


I am guessing such a script might let you override libvirt's mechanism for
adding a VM interface device to the bridge and instead let you directly
configure it using OVS (e.g., ovs-vsctl set port netwin0 tag=6 ).

As I recall, you're not the first person to have this problem so however we
end up resolving it, we should document this better on the OVS site.

dan






> The old conf file mode made running VM's with libvirtd/qemu very
> easy/elegant.
> Do I have any options to get this working with 1.0.0?
>
> Thanks in advance.
>
> Mark
>
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