[Beowulf] Changing BIOS settings on nodes

Steffen Grunewald steffen.grunewald at aei.mpg.de
Thu Sep 27 23:17:50 PDT 2007

On Thu, Sep 27, 2007 at 11:37:23PM -0500, Geoff Jacobs wrote:
> Honest Guvnor wrote:
> > Greetings,
> > 
> > We would like to change the BIOS settings on our compute nodes to
> > enable PXE booting which is disabled by default (AMIBIOS on Intel
> > D875PBZ Pentium 4 motherboard). Reading and writing with /dev/nvram
> > seems to work as expected but reboot fails because of a test against
> > the checksum of the previous BIOS settings. Is there a way round this?

Some BIOSes store their setting not in 128, but 256 bytes. /dev/nvram
usually sees the first half only (minus 14 bytes for the timekeeping).
Obviously, the checksum calculated from 128 bytes is rarely equal to
that obtained from 256 bytes :(

> > The nodes have no video card, there is no support for a serial console
> > in the BIOS but there are floppy disk drives. Any thoughts on
> > alternative ways to change the BIOS?

Even a very simplistic VGA should be standard - how would you handle a 
very early disk failure, or any other emergency of there's no way to 
read out the status of the system that's not running the OS yet?

> > We have the fallback option of putting an Etherboot floppy disk in
> > every node when we want to reinstall but would like to avoid this if
> > we can,

BTW, PXE booting would have to be enabled in two places: in the firmware
part of the ethernet adapter itself, *and* in the boot order. I'm not
aware of any way to do the first step without manual intervention (CTRL-S
or CTRL-B) even if the second step was successful. (Some of us have asked
the board/BIOS maker for a customized version, with PXE booting enabled.)

> This is where the Crash Cart comes into play. You know, the one with the
>  tools, crimper, maybe some spare fans, etc. Usually a monitor and
> keyboard as well.

If there's nothing to connect to you'd be lost with even that.


Steffen Grunewald * MPI Grav.Phys.(AEI) * Am Mühlenberg 1, D-14476 Potsdam
Cluster Admin * http://pandora.aei.mpg.de/merlin/ * http://www.aei.mpg.de/
* e-mail: steffen.grunewald(*)aei.mpg.de * +49-331-567-{fon:7233,fax:7298}
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