Subject: Re: unbootable new disk?
To: Steve Bellovin <>
From: David Laight <>
List: current-users
Date: 11/27/2004 09:11:52
On Fri, Nov 26, 2004 at 09:26:08PM -0500, Steve Bellovin wrote:

Some responses to earlier in the thread...

The "no operating system" error (reported on the original mail) was
probably the "No operating system" error message from the NetBSD 'normal'
mbr code.  The 'bootselect' versions report 'Error 3' instead.

So the 'use entire disk' made to difference.

That error is reported if the first sector of the 'root' partition
definitely doesn't contain the boot code.
This is usually because 'installboot' failed to run properly.
(note that disklabel -B isn't the way to set up that area - except on hp300)

In this case the mbr code will have read sector 63 - and not found the
0xaa55 at the end.  This read should be largely independant of the disk
geometry in use - the sectors/track is almost always 63.

> I changed the BIOS setting for the disk to LBA, from "Auto" (the other 
> choices were "Large" and "C/H/S"); after that, it worked just fine.

That makes this all look like a BIOS bug!
Probably something to do with the geometry translations!
I don't actually know what the BIOS means by 'LBA' and 'Auto', but you
might see the reported geometry change when you select different options.

> Looking back at my postings I see this:
> # fdisk wd1
> Disk: /dev/rwd1d
> NetBSD disklabel disk geometry:
> cylinders: 310101, heads: 16, sectors/track: 63 (1008 sectors/cylinder)
> total sectors: 312581808
> BIOS disk geometry:
> cylinders: 1024, heads: 240, sectors/track: 63 (15120 sectors/cylinder)
> total sectors: 268435455
> Why do the BIOS and NetBSD number of sectors disagree?  The same is 
> true now, with the system running.  Yes, it's a 160G drive, but I have 
> a 160G drive on another machine, and the two geometries give the same 
> total on it.  Is this some BIOS limitation in dealing with a large 
> drive?  And might that have been at the root of my problem?

Well, 268435455 is 0xfffff - which probably means that the BIOS doesn't
support LBA48 reads for disks > 137GB.  You aren't trying to read beyond
that point - at least the failure is being reported before any attempt to
read such sectors (/boot and /netbsd probably have to be below the 137GB


David Laight: