Re: [Xen-devel] Diskless boot at cambridge

[Tim Deegan <Tim.Deegan@xxxxxxxxxxxx>]

On Thu, Apr 14, 2005 at 10:51:14AM -0700, Kip Macy wrote:
> > or XenoBoot (now an optional function of the new Xen demo CD). 
> 
> Is that documented anywhere?

There's a README at
http://www.cl.cam.ac.uk/Research/SRG/netos/xeno/xenoboot/

Xenoboot boots to linux and then runs a script (that it downloads over
https and checks with GPG).  The usual function of the script is to call
'kexec' to load the kernel you're interested in.  The functionality is
being merged with the demo CD (partly so I only have to maintain one of
them and partly because the gentoo package management tools can't cope
any more with upgrading the xenoboot filesystem).  That version hasn't
got documentation yet, but maybe will do soon. :)

> How would you give a machine a unique persistent initiator-name when
> booting from a general cd?

We use its IP address (from statically-assigned DHCP).

Xenoboot is really designed for colo environments: it can be very useful
to have a working linux environment from which to debug a broken
system. :)  Its primary disadvantage in the development environment is
that it makes the reboot cycle longer, as it needs to do a whole extra
Linux boot.  (Its primary advantage is that it supports most NICs.)

If GrUB won't speak to your NIC, there are a couple of ways of using
PXELINUX to boot Xen -- either by wrapping up Xen, xenlinux and dom0's
initrd using mbootpack (in xen-unstable/tools/misc, or from
http://www.tjd.phlegethon.org/software/) and booting that using
PXELINUX, or by building a MEMDISK image that includes GrUB and the xen
images (http://syslinux.zytor.com/archives/2005-March/004941.html).

They both need some preprocessing beyond just sticking the right kernel
in the right place, though.  I'm working on adding support to PXELINUX
to boot Xen directly; hopefully that'll be ready in the next few weeks.

Tim.

-- 
Tim Deegan                           (My opinions, not the University's)
Systems Research Group
University of Cambridge Computer Laboratory

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