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Re: [Xen-users] Xen 3.4.1: pygrub Error: Boot loader didn't return any d

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Subject: Re: [Xen-users] Xen 3.4.1: pygrub Error: Boot loader didn't return any data!
From: Gerry Reno <greno@xxxxxxxxxxx>
Date: Thu, 31 Dec 2009 00:17:21 -0500
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Fajar A. Nugraha wrote:
On Thu, Dec 31, 2009 at 11:27 AM, Gerry Reno <greno@xxxxxxxxxxx> wrote:
I converted a kvm guest to a PV guest converting grub2 to grub and running
update-grub in the guest but it does not want to start.  I remembered to
adjust the indexing from hd0,5 in grub2 to hd0,4 in grub legacy but for some
reason pygrub cannot boot it.  I don't even get a grub prompt.  Can anyone
see anything wrong with this config?

bootloader = "/usr/bin/pygrub"
disk = [ "tap:aio:/var/lib/xen/images/CLOUD-CC-1.img,xvda5,w" ]

First of all, where on earth did you get your conversion instructions from?
This looks like it:

If you install it as HVM, and use the same disk image for PV, then you
should've map it as disk. i.e

disk = [ "tap:aio:/var/lib/xen/images/CLOUD-CC-1.img,xvda,w" ]

instead of

disk = [ "tap:aio:/var/lib/xen/images/CLOUD-CC-1.img,xvda5,w" ]
Yep, tried that.  Same error.

second, AFAIK pygrub doesn't really care about boot sectors or MBR.
That means you could have whatever bootloader originally on the HVM
domU (grub2, extlinux, grub, etc.) and you don't have even have to
install grub or run update-grub to make pygrub works. What you DO
- an active/bootable partition table.
Got that.

This is necessary only if you
map the disk image as disk on domU (i.e. xvda instead of xvda1).
pygrub will then read config from this partition.
- a /boot/grub/menu.lst on the active partition. This file must
contain the correct grub entries.

The original kvm guest had:
/dev/vda5  /boot
/dev/mapper/vg....   /

So I changed all references of /dev/vda5 to /dev/xvda5 in guest. I figured the lvm would take care of itself.

I also tried booting this with the host kernel/initrd but it gets just so far and then the kernel panics. Haven't figured out yet how to get to the /boot partition so I can make changes.


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