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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Invalid Partition Table
Date: 25 Apr 1996 20:20:52 GMT
Organization: Private FreeBSD site, Dresden
Lines: 49
Message-ID: <4lomr4$2qd@uriah.heep.sax.de>
References: <4lb5dh$kuo@paperboy.livenet.net> <4lf930$hmg@uriah.heep.sax.de>
<4ln2hl$kjo@paperboy.livenet.net>
Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch)
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jsloan@LiveNet.Net (Jim Sloan) writes:
>>The drive's real geometry is irrelevant. Use the BIOS geometry.
>>The drive's real geometry is irrelevant. Use the BIOS geometry.
>>The drive's real geometry is irrelevant. Use the BIOS geometry.
>>....
>
>Excuse me? but when I installed FreeBSD it was saying the geometry was
>invalid.
The _detected_ geometry. (Even then, sysinstall might be in error,
since the mapping between BIOS drive numbers and BSD device names is
still an unsolved problem.)
Anyway, all that needs to be known is the BIOS geometry. For 98 % of
the drives that are currently in use, this is a `translated' one (and
for perhaps 90 % of all current drives, the real geometry is even not
uniform across the surface, so it's not useful in terms of the ancient
BIOS geometry idea anyway).
>>Run fdisk, and tweak the C/H/S values of the slice start so they match
>>the relative sector number of the slice start, in terms of the BIOS
>>geometry. Be careful.
>>
>And how do I determine this?
Ask your BIOS. Then, run /sbin/fdisk -u, and correct its idea (you
need to boot from a floppy, or run a fixit floppy for this).
[This is a bogus fdisk table, i'm not using one anyway.]
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
Pick the indicated number, and your BIOS'es idea of the sectors per
track, and heads per cylinder, and recalculate the starting C/H/S
numbers. Take care that sector numbers start with 1 (for hysterical
reasons), while head and cylinder numbers are 0-based.
--
cheers, J"org
joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)