[Fedora-xen] FC6+xen guest boot issue

[Daniel P. Berrange]

On Mon, Nov 06, 2006 at 03:13:28PM -0500, Kanwar Ranbir Sandhu wrote:
> On Mon, 2006-11-06 at 09:19 -0700, Karl Stevens wrote:
> > > Here's what one of my domUs looks like:
> > > kernel = "/boot/vmlinuz-2.6.17-1.2174_FC5xenU"
> > 
> > This is probably why:  you're using FC5, not FC6.  FC6 does away with
> > separate dom0 and domU kernels.
> 
> I should have mentioned that my dom0 is a FC5 box.  I haven't moved it
> over to FC6 for fear of not having any bootable domUs.  Though, it would
> be just as easy to go back to FC5 if that happened.

For x86_64 life is easy - FC5 & FC6 are compatible with each others Xen
guests. For i686 though things are troublesome. The original xen0 & xenU
kernels from FC5 are non-PAE. The xen kernel in FC6 meanwhile is PAE
only. You can't mix & match  PAE with non-PAE between host & guest.
Thus to allow people to mix FC5 & FC6 the more recent kernel errata for
FC5 also contain a PAE enabled kernel -xen  which can be used instead
of the old -xen0 & -xenU

> > > I forgot to mention that running RH7.3 as a paravirtualized domU won't
> > > work since the Xen 3.0 series doesn't have support for the 2.4 kernels
> > 
> > Sorry to correct you, but xensource.com has a domU kernel for RHEL 3
> > (which runs 2.4)
> 
> I didn't know that!  Well, that's certainly helpful.  But, what if one
> is running a RHEL 4? Or some other distro that has a 2.6 kernel?

If you're using x86_64 then you shouldn't have any trouble using DomU
kernels from any other xen-ified distro.  For i686 just make sure you
get the PAE stuff matched up correctly.  WRT to RHEL-4, a future errata
will provide an officially supported Xen guest kernel for the 2.6.9
tree that is in RHEL-4. 

> > I downloaded and used this kernel, and it works (solved my problem.)  I
> > would have rather done things the "Red Hat endorsed" way, but I'm just
> > happy I've got it running.

Given the age of the RHEL-3 kernel & the stage RHEL-3 is at in its product
support lifecycle, it is not practical to provide an officially supported 
paravirt guest kernel.  So either using xensource's unofficial 2.4 backport
is one option, or using fully-virt HVM for the regular RHEL-3 kernel is 
another more supportable option.

Regards,
Dan.
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