Date: Sat, 29 Sep 2001 23:51:43 -0400 (EDT) From: walton@digger.net To: mwm@mired.org Cc: questions@freebsd.org Subject: Re: Partition table problem Message-ID: <20010930035143.94262.qmail@aerre.pair.com>
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You wrote:
> I don't know about sysinstall - I tend to use fdisk/disklabel instead
> of sysinstall for such things. But if it overwrote things in the
> extended partition, you're pretty much hosed anyway.
It shouldn't have. It was only supposed to be writing to the partition
table, not to the partition. Of course, it wasn't supposed to be
altering the partition table, either.... :-/
> > And fdisk will not touch ANYTHING on the disk aside from entry 4 in the
> > partition table, correct?
>
> It won't *change* anything but entry 4. It has to rewrite the entire
> sector - that's the nature of disks. But it reads the sector in and
> then changes just the entry 4 values and writes them back. It may
> offer you chances to change other things - but don't do it.
Rewriting the whole sector is fine by me. I just want to be sure that it's
restricted to that sector and not also trying to do anything with the
logical partition entries inside that partition.
Ok, I've tried 'fdisk -4 -u ad0', but I haven't written the new table it
creates because it's doing something strange. Have a look:
parameters extracted from in-core disklabel are:
cylinders=3876 heads=240 sectors/track=63 (15120 blks/cyl)
Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=3876 heads=240 sectors/track=63 (15120 blks/cyl)
Information from DOS bootblock is:
1: sysid 6,(Primary 'big' DOS (> 32MB))
start 63, size 4188177 (2045 Meg), flag 0
beg: cyl 0/ head 1/ sector 1;
end: cyl 276/ head 239/ sector 63
2: sysid 6,(Primary 'big' DOS (> 32MB))
start 4188240, size 4188240 (2045 Meg), flag 0
beg: cyl 277/ head 0/ sector 1;
end: cyl 553/ head 239/ sector 63
3: sysid 165,(FreeBSD/NetBSD/386BSD)
start 8376480, size 8376480 (4090 Meg), flag 80 (active)
beg: cyl 554/ head 0/ sector 1;
end: cyl 1023/ head 239/ sector 63
4: sysid 15,(Extended DOS, LBA)
start 16752960, size 41852160 (20435 Meg), flag 0
beg: cyl 84/ head 0/ sector 1;
end: cyl 803/ head 239/ sector 63
Should we write new partition table? [n]
Notice the beginning and end cylinders for partition 4. Those are the
settings it gives me when I decline to explicitly specify them. If I
give it the beginning and end (which I believe should be 1024/0/1 -
3876/239/63), then it gives me this:
4: sysid 15,(Extended DOS, LBA)
start 16752960, size 41852160 (20435 Meg), flag 0
beg: cyl 0/ head 0/ sector 1;
end: cyl 804/ head 239/ sector 63
What's going on here? Those values don't make any sense.
Dave
.
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