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RE: Building domains as a lesser user (was Re: [Xen-devel] bootloaders for domain != 0)

  • To: "Jeremy Katz" <katzj@xxxxxxxxxx>
  • From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
  • Date: Fri, 4 Feb 2005 09:38:17 -0000
  • Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Fri, 04 Feb 2005 09:39:32 +0000
  • List-id: List for Xen developers <xen-devel.lists.sourceforge.net>
  • Thread-index: AcUKZv4LFIW0Qpa6RcC9fdtj8ZfKBgANGT7Q
  • Thread-topic: Building domains as a lesser user (was Re: [Xen-devel] bootloaders for domain != 0)

> On Fri, 2005-02-04 at 02:30 +0000, Ian Pratt wrote:
> > One fairly simple option is to use Linux as a domU boot loader. Boot
> > with an intrd, mount the specified filesystem, read off 
> grub.conf, display a menu over
> > the xencons, kexec the appropriate kernel.
> Linux really seems like a very heavy hammer for something like this.
> Even just thinking from a resource perspective, why boot up a whole
> kernel to do nothing more than read an fs and mount another kernel.

I don't buy the resource argument: it takes only a couple of seconds to
boot a xenU kernel to user space, and you're about to be booting another
kernel anyhow.

> Especially as you start thinking about things like modular fs's, etc,
> it's going to be much less clean of a solution and be a significant
> slowdown on your guest boot time.

A few seconds slow down -- nothing compared to what a BIOS normally

I don't see why the filesystems would particularly need to be modular,
though you might do so for convenience. 

> And then, it's yet another kernel to keep updated, etc.

I don't see any reason to keep it up to date. Its running in a protected
environemnt and doesn't have any extra access that the kernel about to
be booted is going to get.
I think this approach will work well.

We already booy all of our *physical* machines using a CDROM containing
a Linux bootloader -- see xenoboot:


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