Message-ID: <477FDEC8.3020605@zytor.com>
Date: Sat, 05 Jan 2008 11:47:20 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Matt Domsch <Matt_Domsch@dell.com>
CC: Gene Heskett <gene.heskett@gmail.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Querying the bios from booted linux kernel?
References: <200801041913.54030.gene.heskett@gmail.com> <20080105041828.GB6011@auslistsprd01.us.dell.com>
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Matt Domsch wrote:
> 
> parted and fdisk both write into the MBR signature space, so your
> disks should have unique MBR values in them.
> 

parted did so incorrectly, and had less than 20 bits of randomness.

fdisk only does so as of a very recent version (I put that in after I 
noticed a whole bunch of disks I had had zero identifiers.)

sfdisk doesn't at all, last I checked.

None check for collisions.

> I've given up trusting any BIOS to get EDD 3.0 device paths right,
> there are just too many broken implementations out there, and
> seemingly no real desire on the part of the component vendors to fix
> it.  MBR signatures work pretty well - Dell uses this method for every
> one of our factory installed Linux systems we ship, so I _know_ it works.

At least with a known distribution.  But yes, it really seems to be the 
most reliable method.

	-hpa


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