Subject: Re: Booting sd0 q(disk geometry versus bios geometry)
To: Todd Whitesel <firstname.lastname@example.org>
From: Frank van der Linden <email@example.com>
Date: 07/13/1998 14:29:16
On Mon, Jul 13, 1998 at 04:49:13AM -0700, Todd Whitesel wrote:
> This all causes me to wonder if there isn't some way of diagnosing what the
> BIOS thinks each disk looks like, so that we can eliminate the guesswork. I
> bought The Complete FreeBSD 2nd Edition so I could check out their installer
> and documentation; they determine the BIOS geometry somehow and supply it as
> a default in their FDISK phase of installation. While you can change the BIOS
> geometry from that program, their installation instructions don't talk about
> it as it's probably a bad idea unless you really know what you're doing.
The mechanisms for making BIOS geometries available to the kernel are
there, but they're not being used at the moment. The major problem is
that you can not make a 100% proof connection between BIOS drive numbers
and NetBSD numbers. Some assumptions are safe, for example: if you have
only one IDE disk, wd0 will be BIOS drive 0. But there may be other
situations, for example if you mix SCSI and IDE drives. Also, nothing
stops a user from compiling a kernel with wd0 being the 2nd IDE disk,
and wd1 being the first.
Having said that, the current method clearly needs improvement, and the
above probably would be better, with the option for the user to check
things. Although most people do not seem to do this.