Subject: Re: i386 booting, take 2
To: None <>
From: Phil Nelson <>
List: tech-install
Date: 09/21/1998 09:21:40
>Personally, I thought the goal was to make it easy.

Yes, I agree.  I was hoping to allow the user to ignore all geometry
issues by what I proposed, except in the rare case where the disk
could not be matched to the BIOS geometry.  Your proposed method
of matching the disks could improve the percentage of disks matched
by a bit.

But I still believe that the reported geometry via the ioctl that
gets the geometry should be what the disk reports, not what the BIOS
reports.  (The user does not have to know about this if sysinst and
others are done correctly.  The only reason currently that sysinst
asks about the BIOS geometry is because fdisk is prone to get things
wrong and we need to ask the user for help.  With a much better
method of matching disks to BIOS geometry, we don't have to ask.)

As I understand it, to be able to use the entire capacity of SCSI
disks (and possibly IDE disks), we need to do one of two things:
	a) choose a fake geometry that allows one to address
	   as much of the capacity as possible (as sysinst now
	   does) or
	b) rewrite newfs to use the entire capacity regardless of
	   what the C/H/S geometry says.  (Given that FFS works with
	   cylinder groups, this may be hard.  From what I remember
	   in adapting the FFS code to run under minix and build
	   FFS file systems, the FFS is heavily tied to C/H/S
	   geometry data.)

Further direct comments about
>Subject: i386 booting, take 2

>If you are using the whole boot disk for NetBSD, it's recommended that
>you put the root partition at the beginning of the disk.  This will
>overwrite the DOS MBR (`master boot record') with the beginning of the
>NetBSD boot program.  If you do this, you do not need to worry about
>the geometries used by the BIOS, BOS MBR or NetBSD disklabel; you can
>use arbitrary values, provided they are large enough to cover the
>whole disk.  If you're installing this way, you can skip the rest of
>this section.

If I understand what you are saying here, this CAN NOT be done on
all machines.  I have HP machines here at WWU that refuse to boot
from any partition that contains the very first track on the disk.
I can try again, but unless things have changed since 1.2 in
terms of the boot support, I'm sure it can't be done.

>If you are installing NetBSD on a disk other than the first BIOS
>device, and it has not previously been formatted under DOS, then you
>will need to determine the `geometry' for this device manually.  For
>an IDE/ATA disk, this information is available in the `standard
>configuration' section of the BIOS setup program.  For a SCSI disk, it
>may be available from the SCSI setup utility, or it may not be
>available at all.  [Should we also add a mechanism to query the BIOS

This is also not true.  I have had machines I used where the 
setup program in the BIOS told me ONLY the "real" (reported) 
geometry of the disk and not the what the BIOS used.  This was
for a disk smaller than the 8G limit.  The ONLY way I could
find out what the BIOS used for the MBR was to use pfdisk.

In rereading "take 2", it appears that what you wrote is intended to
be part of the install document.  I believe that we should be able to
do a good enough job to not have any geometry information in the
install document except possibly in a section that talks about
"expert" installations and trouble shooting.  There really should be
no reason that users should have to know anything about the geometry.

Phil Nelson (NetBSD/pc532 machine) (work)