Date: Sun, 24 Nov 1996 10:28:02 +1100 From: Bruce Evans <bde@zeta.org.au> To: msmith@atrad.adelaide.edu.au, phk@critter.tfs.com Cc: fenner@parc.xerox.com, freebsd-current@freebsd.org, jkh@freebsd.org, stesin@gu.net Subject: Re: 2.2-ALPHA install failure Message-ID: <199611232328.KAA07967@godzilla.zeta.org.au>
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>Hmm, we could try to write the fake MBR so it represents some sane
>geometry in that particular case. That would help i guess.
Why not write the normal historical_bogus_partition_table which is
specially handled in the kernel so that there are no problems? It's
possible that it is not specially enough handled by the SCSI BIOS,
but there seem to be no problems in practice.
>Somebody with an NCR will have to do it though.
It works fine with an NCR:
!******* Working on device /dev/rsd0 *******
!parameters extracted from in-core disklabel are:
!cylinders=6703 heads=5 sectors/track=126 (630 blks/cyl)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ as reported by SCSI enquiry
!
! Figures below won't work with BIOS for partitions not in cyl 1
!parameters to be used for BIOS calculations are:
!cylinders=6703 heads=5 sectors/track=126 (630 blks/cyl)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ same, because the partition table
is recognized as garbage and doesn't
override it. Don't use this for a
real partition table.
![<UNUSED>...]
!The data for partition 3 is:
!sysid 165,(FreeBSD/NetBSD/386BSD)
! start 0, size 50000 (24 Meg), flag 80
! beg: cyl 0/ sector 1/ head 0;
! end: cyl 1023/ sector 63/ head 255
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Normal historical_bogus_partition_table which indicates a 1023/256/63
geometry. It would be valid if it size were 1023*63*256 instead of
50000. Note that it has 256 heads, not 255. Some SCSI BIOSes can't
handle 256 heads, but the ncr BIOS can.
>I belive you can get away with it if you use the 2.2-ALPHA boot
>floppy, and use the wizard mode in the fdisk menu.
Too hard for me ;-). I use something like `cp /usr/mdec/boot1 /dev/rsd0'
or `disklabel -B sd0' or type in the above partition table. The disklabel
-B method only works on dedicated disks, which is the only case under
discussion. At least, it used to work. Disklabel now does extra work to
preserve the existing partition table if there is a nonzero entry in it.
Bruce
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