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[Xen-devel] Deficiencies in guest bootloader design

To: "Xen Devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Deficiencies in guest bootloader design
From: "Michael Paesold" <mpaesold@xxxxxx>
Date: Thu, 13 Apr 2006 16:29:23 +0200
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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.

The problem is that the bootloader is not called from Xend, after virtual block devices are setup, but instead it is called directly from xm, i.e. in xm/create.py.

If I have looked correctly, (1) a bootloader cannot be used for devices such as nbd: or enbd: devices, and (2) a bootloader cannot be used when accessing Xend via XML-RPC (or libvirt or similar), because the whole notion of a "bootloader" at domain creation time is only available in "xm", but not in Xend.

It should be fixable, since at least on guest *restart*, xend/XendDomainInfo.py already uses the bootloader to re-extract the kernel image from the vbd.

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.

There are some issues though. In XendDomainInfo.initDomain, image.create is done before self.createDevices. Can this be changed easily?

Thanks for any help or guidance.

Best Regards,
Michael Paesold

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