Re: [Xen-users] Best way to convert pv to hvm?

[Tim Post <tim.post@xxxxxxxxxxx>]

On Tue, 2007-06-05 at 09:52 +0100, Nico Kadel-Garcia wrote:
> Tim Post wrote:
> > On Tue, 2007-06-05 at 01:08 +0100, Tony Hoyle wrote:
> >   
> >> Hi,
> >>
> >> I'm trying to convert a number of PV domains to HVM domains.  The snag 
> >> is they're all in separate partitions, so I need to get a unified disk 
> >> image.
> >>
> >> My current plan is to mount the root of dom0 inside a booted domu 
> >> (single user mode) and dd the entire contents of the virtual disk 
> >> /dev/sda into a file on the dom0 disk.  Is this likely to work?  It's
> >> gonna be slow I know due to the dom0->domu->dom0 translation but is 
> >> there perhaps a faster way?  I presume xen itself creates a partition 
> >> table somewhere and if I could get at that and do it entire thing in 
> >> dom0... is this just a python script generating it at runtime or is it 
> >> stored somewhere?
> >>
> >> Tony
> >>     
> >
> > Why not setup the hvm guests to use nfsroots with a brand spanking new
> > unpartitioned image as well? Just fdisk, format, copy over adjust
> > config / boot paramaters and reboot.
> >
> > This also lets you work the neuances you'll need to address in udev and
> > others when converting. Well , may need to. I have no idea what you have
> > or I'd make more distro specific suggestions.
> >
> > Just setup the nfs server on dom-0. I don't use HVM much, but I don't
> > see any reason why that wouldn't work.
> >
> > Seems like the easiest way to go for me. Its quite easy to break up var/
> > usr/ and the rest doing it like that.
> >   
> 
> Hmm. You're going to have fun and games with partitioning. If you're 
> using a system that does network boot well, it may be feasible to 
> pre-transfer your OS images into an appropriately built lfile image or 
> partition, then use a "rescue" boot mode to boot ot the console form 
> installation sources and successfully set up grub or something else.

Well, he did say from PV to HVM, I can't think of anything PV that can't
be made to play nicely with a NFS root. But there very well may be.

You can install grub and stuff prior to starting the process via the PV
guests OS packaging mechanism which also gives you the appropriate
native kernel and modules in most cases, commonly people forget about
the modules and wonder why it won't boot.

I guess my method could be a nightmare if circumstances were just right,
but I've yet to run into those circumstances even with older kernels.

My lab mate just installs a vanilla version of the PV guest on a new hvm
domain, lomounts it and copies the old stuff over. Always works for him
but I'm not quite that brave. This same person drinks 5 cups of coffee +
4 'generic jolt' colas per day.

Best,
--Tim


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