Date: Thu, 7 Jan 1999 01:57:35 +0200 (SAT) From: Robert Nordier <rnordier@nordier.com> To: asami@FreeBSD.ORG (Satoshi Asami) Cc: bde@zeta.org.au, freebsd-current@FreeBSD.ORG Subject: Re: How to Build & Run ELF Kernel Message-ID: <199901062357.BAA03690@ceia.nordier.com> In-Reply-To: <199901062306.PAA47473@silvia.hip.berkeley.edu> from Satoshi Asami at "Jan 6, 99 03:06:52 pm"
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Satoshi Asami wrote:
> * disklabel -B -b /boot/boot1 -s /boot/boot2 <disk>
>
> I did this and one of my machines have trouble reading the
> bootblocks. It just says "read error" after OS-BS selects the disk.
>
> I tried it with
>
> disklabel -B /dev/rsd0s2c
> disklabel -B -b sd0s2
> disklabel -B -b /boot/boot1 -s /boot/boot2 sd0s2
>
> etc. It's always the same, disklabel exits without an error but it
> fails during reboot.
>
> Any ideas?
The new boot1 will report a "Read error" on any of the following:
o Can't get the disk geometry from the BIOS
o The disk geometry would cause division by zero
o The derived cylinder number exceeds 1023
o BIOS fails to read a sector on five consecutive attempts
I'd check particularly whether the FreeBSD slice entry is 100%
correct.
The old bootblocks use the CHS value (257/1/1 below) to determine
the slice offset, whereas the new bootblocks use the start value
(4128768 below) and the disk geometry reported by the BIOS to derive
a CHS:
[Sample fdisk output]
sysid 165,(FreeBSD/NetBSD/386BSD)
start 4128768, size 4305357 (2102 Meg), flag 80 (active)
beg: cyl 257/ sector 1/ head 1;
end: cyl 524/ sector 63/ head 254
sector = 4128768 % 63 + 1 = 1
head = 4128768 / 63 % 255 = 1
cyl = 4128768 / 63 / 255 = 257
--
Robert Nordier
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