Date: Mon, 10 Dec 2001 11:50:10 +0000 From: Ian Dowse <iedowse@maths.tcd.ie> To: Peter Wemm <peter@wemm.org> Cc: Joerg Wunsch <joerg_wunsch@uriah.heep.sax.de>, freebsd-current@FreeBSD.ORG Subject: Re: cvs commit: src/sys/kern subr_diskmbr.c Message-ID: <200112101150.aa33241@salmon.maths.tcd.ie> In-Reply-To: Your message of "Sun, 09 Dec 2001 16:43:50 PST." <20011210004350.6703C3810@overcee.netplex.com.au>
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In message <20011210004350.6703C3810@overcee.netplex.com.au>, Peter Wemm writes
:
>The problem is, that you **are** using fdisk tables, you have no choice.
>DD mode included a *broken* fdisk table that specified an illegal geometry.
...
>This is why it is called dangerous.
BTW, I presume you are aware of the way sysinstall creates DD MBRs;
it does not use the 50000 sector slice 4 method, but sets up slice
1 to cover the entire disk including the MBR, with c/h/s entries
corresponding to the real start and end of the disk, e.g:
cylinders=3544 heads=191 sectors/track=53 (10123 blks/cyl)
...
The data for partition 1 is:
sysid 165,(FreeBSD/NetBSD/386BSD)
start 0, size 35885168 (17522 Meg), flag 80 (active)
beg: cyl 0/ head 0/ sector 1;
end: cyl 1023/ head 190/ sector 53
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>
Otherwise the disk layout is the same as disklabel's DD. I suspect
that this approach is much less illegal than disklabel's MBRs
although I do remember seeing a HP PC that disliked it. I wonder
if a reasonable compromise is to make disklabel use this system for
DD disks instead of the bogus 50000 sector slice? Obviously, it
should also somehow not install a partition table unless boot1 is
being used as the MBR, and the fdisk -I method should be preferred.
Ian
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