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Re: [Xen-users] Problems converting FC8 HVM guest to PV

To: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Problems converting FC8 HVM guest to PV
From: Jason Solan <jsolan@xxxxxxxxxxxxxxxxxxxx>
Date: Thu, 27 Dec 2007 21:22:46 -0500
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On Thu, 2007-12-27 at 19:57 -0500, jim burns wrote:
> On Thursday 27 December 2007 06:35:54 pm Evan Lavelle wrote:
> > title Fedora (2.6.21-2952.fc8xen.xenblk)
> >   root (hd0,0)
> >   kernel /xen.gz-2.6.21-2952.fc8
> >   module /vmlinuz-2.6.21-2952.fc8xen ro root=LABEL=/ rhgb quiet
> >   module /initrd-2.6.21-2952.fc8xen.xenblk.img
> Since it's likely to be slow on the list now, I'll give this a stab, tho' 
> I'll 
> warn you I haven't actually done this myself. However, some things stand out:
> The reason Plan A didn't work is you can't load the xen hypervisor (xen.gz) 
> inside a domu. Try deleting the 'kernel /xen.gz...' line and 
> change 'module /vmlinuz...' to 'kernel /vmlinuz...'. I personally would use 
> the original fc8 /initrd-2.6.21-2952.fc8xen.img. At a minimum, a custom 
> initrd also has to have '--preload=xennet'.

I don't have my notes in front of me, but I believe Jim pretty much
nailed it (at least with option A).
I've done several HVM -> PV conversions and always use the first option
you described.
For fedora it comes down to: 
yum install kernel-xen
mkinitrd --preload=xenblk --preload=xennet
(if you don't have xennet your domU will still work, but you won't have
a network at boot, you can modprobe xennet after boot if you forget)

Modify the grub config of the domU:
  title Fedora (2.6.21-2952.fc8xen.xenblk)
    root (hd0,0)
    kernel /vmlinuz-2.6.21-2952.fc8xen ro root=LABEL=/ rhgb quiet
    initrd /initrd-2.6.21-2952.fc8xen.xenblk.img

And switch the config file to use pygrub

If you have any issues, just post back to the list.  I'll be able to get
my notes tomorrow.

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