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SubjectRe: System unique identifier.....
Date
Ted Tso wrote:

> From: Matthew Jacob <mjacob@feral.com>
>
> At any rate, this was all quite helpful. A user space UUID generator can
> generate the seed WWN. I'll figure out some clever place to put it so
> that a driver can get at it. It'd be nice if this was a generalizable
> persistent system metadata solution that was not a per-platform different
> mechanism (you know, OBP NVRAM for sparc, SRM NVRAM for Alpha, lilo
> extensions for i386...).
>
> Yes, this should work. I agree it would be nice to have a
> architecture-indepedent persistent system metadata that was accessible
> very early in the boot process. But that really isn't realistic.
>

I am afraid that even that is not that simple. In case of Alpha, for
example, some machines may have in NVRAM SRM console, some may have
ARC BIOS, some both, and may or may not have free blocks of NVRAM.
But even if such free blocks exist you never know where because
different versions of firmware, even on a board of the same type, do
have different sizes and possibly different things were already stored
into NVRAM (like milo - Linux MIni Loader - itself, which happens
sometimes). Also an access to NVRAM may be not there once you booted
and hacking firmware is not a very exciting proposition.

So the only place left seems to be a Linux boot image which can
be of two different types. One for booting via ARC/milo and the
other for booting from SRM with 'aboot' present or not. Then you
are running into a problem already noted by Ted that this image
may, or may not, be accessible once Linux booted. Usually it is,
for a pure convenience sake, but there are no guarantees.

Michal
michal@harddata.com


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