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Re: [Xen-devel] Deficiencies in guest bootloader design

To: Anthony Liguori <aliguori@xxxxxxxxxx>
Subject: Re: [Xen-devel] Deficiencies in guest bootloader design
From: Michael Paesold <mpaesold@xxxxxx>
Date: Thu, 13 Apr 2006 20:09:20 +0200
Cc: Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ewan Mellor <ewan@xxxxxxxxxxxxx>
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Anthony Liguori wrote:
Ewan Mellor wrote:
On Thu, Apr 13, 2006 at 04:29:23PM +0200, Michael Paesold wrote:
I have tried to use a dynamically activated block device with pygrub (actually drbd, but could be enbd, nbd, or simply any vbd other than phy: or file:). That does not work.
Is there anyone working on bootloader improvements? If not, is a change to move the bootloader stuff from xm to Xend acceptable? In that case I could try to come up with a patch.

Certainly such a patch would be accepted.

Just as a warning, it's not going to be simple to run something like pygrub from Xend. The reason it runs from xm now is that it needs to interact with the user. If it were launched from Xend, it need to find a way to attach to a PTY that xenconsoled would use so that it can display the text over the normal console before actually launching the domain.

It's certainly not impossible but it touches quite a few things.

Thanks for that important hint. Hmm, output of pygrub is only really important in the case when xm create is called with -c. In that case the console must be setup anyway, but I guess that this only happens after at least part of the guest initialization.

After reading through past discussion, I have a feeling that porting real boot loaders to xen (e.g. grub) would be a better long term solution.

Just for booting linux, pygrub is really ok, and I prefer it over domUloader because it relies on existing infrastructure in domU (menu.lst) to get the correct kernel to boot ("yum update" inside domU will do the right thing once grub configuration is setup correctly).

On the other hand pygrub only handles ext2/3 and reiserfs, so booting a bsd guest won't work easily.

Best Regards,
Michael Paesold

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