Re: [Xen-users] xen3 domU on xen4 dom0

[Henrik Langos <hlangos-xen@xxxxxxxxxxxxxx>]

On Tue, Feb 08, 2011 at 03:26:50PM +0000, Todd Deshane wrote:
> On Tue, Feb 8, 2011 at 2:17 PM, Wolf Grossi <wg@xxxxxxxxxxxxxx> wrote:
> > Greetings!
> >
> > Trying to to run a xen3 domU on a xen4 dem0 I run into problems.
> >
...
> > With
> > xm create -c M08
> > I get the following error:
> >
> > XEN1:/etc/xen/vm # Error: (2, 'Invalid kernel', 'elf_xen_note_check: ERROR:
> > Xen will only load images built for Xen v3.0\n')
> >
> > I do not uderstand the above error: the kernel to be loaded *is* a xen-3.0
> > kernel and should be taken from domU:/boot.
> >
> > Now I have the following questions:
> > 1) Can I run xen-3 domU's on a xen-4 dom0?

Yes. I am running a Debian Squeeze Xen 4.0.1 Hypervisor and 2.6.32-5-xen-amd64 
dom0.

On that I run a couple of older PVM machines that have an 2.6.26-2-xen-686 
kernel.
That is a 32bit kernel compiled for xen 3.2-1.

Tomorrow I'll try to get my old Etch VMs there too. (2.6.18 32bit domU made for 
Xen 3.0.3)

> > 2) If yes (hope so :-), what's wrong with the above install/config,
> >   or what have I missed?

I guess your pygrub doesn't find the right kernel on your VM's disk image.

Try to mount the image in dom0, copy the kernel and initrd to /boot/foo/

Edit your config file /etc/xen/vm/M08 and replace

 bootloader      = '/usr/lib/xen-default/bin/pygrub'

with

 #bootloader      = '/usr/lib/xen-default/bin/pygrub'
 root = '/boot/foo/vmlinuz-blah'
 ramdisk= '/boot/foo/initrd-blah'

Don't forget to umount the VM's disk image and try again
xm create /etc/xen/vm/M08

Good luck :-)

> 
> You need the "top" Xen version to run as an HVM guest on the bottom
> Xen. So, for your case, make your Xen3 Xen domU an HVM domain. That
> should work.
>
> Hope that helps.
> 
> Thanks,
> Todd

AFAIK pygrub is only for PVM, isn't it? So I assume that Wolf tries 
to get an older PVM guest to run on a relatively recent hypervisor/dom0

cheers
-henrik


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