Re: [Xen-users] FullVirt to ParaVirt

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I have a linux distro SME 7 that uses the 2.6.9-55.0.2.ELsmp #1 SMP
> kernel. I would like to be able to set it up as a paravirtual instead
> of fullvirt. I have been following the "Convert physical server to VM"
> thread, would this work the same way for converting this distro to a
> paravirt setup?

I'd expect the conversion process to be rather similar.  It might actually be 
easier...

You could compile a Xenified kernel for that OS image and build an appropriate 
initrd.  Then you could either add a "boot Xen-aware kernel" option to your 
menu.lst, or copy the kernel image + initrd to dom0's filesystem and specify 
them directly in the paravirtual domain config.

Once you've built an appropriate paravirtual-style config for that domain, you 
can boot it using xm create (and selecting the right kernel, if you elected 
to use pygrub and store the kernel / initrd in the domain's filesystem).

Keep your fingers crossed, and the domain will probably detect that a load of 
hardware (corresponding to the HVM machine it was installed in) has 
disappeared, and that some new hardware (corresponding to the PV devices) 
have arrived.  You'll need to e.g. configure networking to work with the new 
devices.  To make the disks work, you could either configure the block driver 
to export disks as hd* (to match your HVM config) or alter settings in the 
guest to use xvd* directly.  If your guest uses LABEL= or UUID= to mount 
filesystems then this shouldn't even be necessary.

Using this approach, you could probably even get the same image to "dual boot" 
between HVM and PV modes by using a different xm config for each.  You'd have 
to handle the distro's hardware detection grumbling about the hardware 
changes each time you switched modes, and you'd need to make sure the network 
came up correctly despite the net device changing!  (same for block, if 
you're using device names directly)

Hope that helps some.  I'm suffering from caffeine withdrawal headaches right 
now (coffee shortage), so I'm not at my best - I apologise for any 
inaccuracies.

You might want to copy the VM's disk and try this all out on the copy.  
That'll mean you can preserve the original HVM domain until you're sure the 
conversion has worked.

HTH!
Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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