Re: [Xen-devel] Re: PXE boot - Ian Pratt - com.xensource.lists.xen-devel

13 messages in com.xensource.lists.xen-develRe: [Xen-devel] Re: PXE boot

From	Sent On	Attachments
Ruediger Berlich	28 Jul 2004 08:04
Ian Pratt	28 Jul 2004 17:54
Ruediger Berlich	28 Jul 2004 18:15
Ian Pratt	29 Jul 2004 00:32
Mike Brady	29 Jul 2004 02:13
Yan Li	29 Jul 2004 02:16
Steven Hand	29 Jul 2004 02:20
Yan Li	29 Jul 2004 03:32
Steven Hand	29 Jul 2004 03:52
Steven Hand	29 Jul 2004 03:55
Yan Li	29 Jul 2004 04:37
Fredrik Dahlberg	29 Jul 2004 08:30
Adam Heath	29 Jul 2004 09:59

Subject:	Re: [Xen-devel] Re: PXE boot
From:	Ian Pratt (Ian....@cl.cam.ac.uk)
Date:	07/29/2004 12:32:31 AM
List:	com.xensource.lists.xen-devel

Hi there,

Xen currently doesn't support booting domains via PXE, though at some point someone talked about adding it. Basically, the domain builder would do the PXE request and tftp the kernel image that would be place in the domain.

I'm sure you could get the domains booting sans PXE without too much hassle anyhow.

I would assume that it would probably be sufficient to modify the domain builder in a way that, upon request, it executes a script (kind of like a constructor) before the domain starts up. One could do things like setting up a disk image with all needed data (like the kernel image) in that. As everything is physically handled in domain0, this could easily replace the PXE boot. And one could of course do many other cool things in such a constructor (and destructor type) script. Or maybe I'm wrong.

The domain's kernel image is placed in memory by the domain builder, so doesn't need to come off the domain's virtual disk.

PXE is basically a combination of DHCP and tftp.

We could have the domain builder issue a DHCP request using the domain it's building's MAC address, then use tftp to fetch the kernel image into a temporary file that the domain builder can then use.

Adding support to xend to do this shouldn't be hard. The only slightly non trivial bit is sending a DHCP request using someone else's MAC -- rather than hacking dhclient it's probably easiest to hand craft something one-shot as you don't need a daemon (presumably you can rely on the server giving the same address to the same MAC if asked in quick succession)

Ian