[Beowulf] reboot without passing through BIOS?

Lombard, David N dnlombar at ichips.intel.com
Thu Jul 31 09:43:29 EDT 2008


On Wed, Jul 30, 2008 at 11:27:22AM -0700, Robert G. Brown wrote:
> On Wed, 30 Jul 2008, David Mathog wrote:
> 
> > David Lombard wrote:
> >
> >> On Wed, Jul 30, 2008 at 09:13:56AM -0700, David Mathog wrote:
> >>> It then occurred to me that doing so would
> >>> require a trip through the BIOS on every reboot, at least on every x86
> >>> based computer I'm familiar with.
> >>
> >> Not since kexec was added to the kernel!
> >
> > That's exactly what I was thinking of for the Beowulf node problem.
> > For instance:
> >
> >  http://www.knoppix.net/forum/viewtopic.php?t=27192
> >
> >> Beyond using kexec as described above, grub directly supports this; lilo
> >> did too.
> >
> > I know how to do this by changing the configurations, but not how to
> > specify a one time change that doesn't need to be manually undone later.
> > Is either of these boot loaders capable of doing the logical equivalent of:
> >
> >  grub-next-boot-only -default 3
> >
> > (Override whatever default is in the config file, but just for the next
> > boot.)
> 
> There are several ways to accomplish this, and they can be automated.
> For example, run a script at boot time that runs a script like
> /etc/specialboot if it exists.  Then put:
> 
> #!/bin/sh
> 
> # cp /boot/grub/grub.conf.default /boot/grub/grub.conf
> # cp /boot/grub/grub.conf.special /boot/grub/grub.conf

According the the FM, there's a "grub-set-default" program that does
the trick.  It supposedly creates a "default" file in the grub directory,
nominally /boot, that causes grub to behave differently.  That's what I
was alluding to in my first post.  Sadly, no such program exists in my F7.

GIYF teaches us that the new method is:

  # echo "savedefault --default=2 --once" | grub --batch
  # reboot

where "2" is the choice for your next one-time boot.

I haven't tried this; I did use the LILO method when it was the bootloader
of choice...

-- 
David N. Lombard, Intel, Irvine, CA
I do not speak for Intel Corporation; all comments are strictly my own.
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