[Beowulf] motherboards for diskless nodes

Robert G. Brown rgb at phy.duke.edu
Fri Feb 25 12:38:10 EST 2005


On Fri, 25 Feb 2005, Alpay Kasal wrote:

> Donald Becker just mentioned "RPL", I do believe that is what I was
> referring to in my last response.
> 
> >PS: PXE is not the only embedded method of bootnic. I forget the other
> method but it's often paired with onboard realtek8139's, an old intel
> standard (?) which is useless these days but still found on some new
> motherboards. Maybe someone else here knows what I'm referring too.

I imagine you're referring to bootp or etherboot.  bootp is a part of
PXE.  Most PXE implementations currently use dhcp and/or bootp followed
by tftp.  These in order do NIC TCP initialization, path/config
information exchange, retrieval of a bootable image.  At that point
control is passed to a second stage bootloader (usually in ROM BIOS)
that boots the retrieved image.  Google is as always your friend and can
find you anything from HOWTOs to Intel white papers that precisely
define the process (that I'm describing very coarsely).

The reason I put and/or is that dhcpd typically does both of the first
two steps nowadays -- it isn't necessary to have a separate bootp
daemon.  Once upon a time when Sun sold lots of diskless workstations
(by design) there was, but the loader sequence was more or less the same
but without dhcp -- a bootparamd handling bootp and network
initialization, tftp to retrieve an image in RAM, a local ROM loader to
boot it.  There is also the issue of PXE (per se) and etherboot (per se)
-- see e.g.

  http://www.ltsp.org/documentation/pxe.howto.html

Basically, this just involves what kind of image is passed back to the
boot loader -- a lzpxe image (bootable image packed up for PXE) or a nbi
(network bootable image) and what actually does the boot loading.

For MOST users, all of this is irrelevant and not worth knowing or
worrying about -- at most it alters how you prepare the bootable image
for actual transfer and loading at the other end.  To boot with PXE, you
just set up dhcp and tftp (on a server) appropriately, using
instructions available lots of places on the web.  The image you boot
and what happens afterward is completely under your control -- we
routinely boot a dos image via pxe, for example, to relash a BIOS or run
memtest86 via PXE.  You can find a free open source DOS floppy image a
variety of places on the web, e.g. here:

  http://www.freedos.org/freedos/files/

(Note that dos on such a floppy doesn't do very much, typically -- it
functions pretty much strictly as a bootable program loader and
execution environment with an associated (fairly small) set of BIOS
calls and resource hooks built in.  Not much of a kernel...)

HTH -- I'm skipping a lot of detail (and may even be getting some of it
wrong:-) but you can find that detail on the web and read to your
heart's content, if it matters to you.

   rgb

> 
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-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu


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