[Beowulf] reboot without passing through BIOS?

Robert G. Brown rgb at phy.duke.edu
Wed Jul 30 14:27:22 EDT 2008


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

in it.  Copy grub.conf into the two files.  Edit special to boot your
special configuration, let the other one save out as the default/restore
point.  copy the special to grub.conf.  Boot.  Uncomment the script line
that puts back the default and boot.

Plus infinite permutations of the general idea.  We used to have
something very similar set up for hot installs.  There may be better
ways to do it now, but this is easy to understand and implement and will
work.

    rgb

>
> Thanks,
>
> David Mathog
> mathog at caltech.edu
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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-- 
Robert G. Brown                            Phone(cell): 1-919-280-8443
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