Date: Mon, 27 Mar 1995 02:46:07 +1000 From: Bruce Evans <bde@zeta.org.au> To: current@FreeBSD.org, uhclem@nemesis.lonestar.org Subject: Re: Invalid DOSpartition table may be a bad idea Message-ID: <199503261646.CAA27307@godzilla.zeta.org.au>
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>[2]If there is no DOSpartition table then there is one slice (the whole >[2]disk). Unfortunately you have to have a DOSpartition table to boot with >[2]biosboot, and disklabel -B writes a dummy DOSpartition table whether you >[2]want it or not. Fortunately it writes an _invalid_ DOSpartition table. >If I understand what you are saying here, this may be a bad thing. >Windows 95 (which I have to run on some systems at work) takes a disk with >a missing or invalid partition table as an open invitation to automatically >initialize the entire disk for Windows 95 by putting a "use entire disk" >DOS partition table in there. The FreeBSD invalid DOSpartition table is historical baggage. I haven't been able to eradicate it. Perhaps Windows 95 will do a better job :-). What does Windows 95 consider to be an invalid table? We want a table with one partition that covers the whole disk _including_ the MBR to be valid, but that may be an invalid table for DOS. The slice driver does the following validity checks: 1) Last 2 bytes in MBR must be 0x55, 0xAA, else table is ignored. 2) For each partition, the C/H/S start and end must equal the logical start and end, else a warning is printed. The logical start and end are always considered valid. If the logical start or end corresponds to a C >= 1024, then no warning is printed in the following cases: a) C = 1023, H = max, S = max. b) C = correct mod 1024, H = correct, S = correct. It doesn't do any overlap or ordering checks. Bruce
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