Date: Tue, 21 Nov 2000 09:44:48 +1030 From: Greg Lehey <grog@lemis.com> To: John Summerfield <summer@OS2.ami.com.au> Cc: freebsd-stable@FreeBSD.ORG Subject: Re: Dedicated disks (was: Dangerously Dedicated) Message-ID: <20001121094447.Y58333@echunga.lemis.com> In-Reply-To: <200011201003.eAKA3RS01865@possum.os2.ami.com.au>; from summer@OS2.ami.com.au on Mon, Nov 20, 2000 at 06:03:27PM %2B0800 References: <grog@lemis.com> <200011201003.eAKA3RS01865@possum.os2.ami.com.au>
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On Monday, 20 November 2000 at 18:03:27 +0800, John Summerfield wrote: > > grog@lemis.com said: >> On Sunday, 19 November 2000 at 23:57:25 -0800, David O'Brien wrote: >> On Mon, Nov 20, 2000 at 02:53:04PM +1030, Greg Lehey wrote: >> >> If >> it shows valid partitions, you're using a Microsoft partition table. >> ^^^^^^^^^^^^^^^^^^^^^ >> Greg, can you read English?? Can you comprehend it?? Are you bind >> and in >> a write-only mode?? >> For the last time IT IS NOT A MICROSOFT PARTITION TABLE but a PC BIOS >> PARTITION TABLE AND DICTATED BY THE INTEL x86 PLATFORM. THEY ARE ALSO >> REQUIRED BY THE IA-64 PLATFORM. > >> Why do you *insist* on calling it a "Microsoft partition table"?? > >> Hmm. I was going to say "Because it was introduced with Microsoft >> 2.0", but I'm no longer so sure. Reading the MS-DOS 2.11 source code, >> it seems that they didn't have a partition table at the time. Can >> anybody remember when it was introduced? > > Nothing to do with the PC BIOS: > 1. The PC did not support fixed disks (introduced with the XT). The PC > understood floppy disks and cassette tape. Well, yes, there were various PCs. I was implicitly referring to the XT in this case. > 2. The BIOS has enough intelligence to read the first sector from a disk and > then jmp into it. This sector is called the Master Boot Record, and it > contains the original partition table and code with enough intelligence to > find the active partition, read a teensy bit of it (using BIOS calls) and pass > control to the code read in this manner. > > If you want a dedicated BSD disk, you replace this code with equivalent code > to find where BSD lives. Or Solaris. > > In the original implementation of these partitions, one could have no more > than four. Of these, only one could be active and so PCDOS/MSDOS didn't need > code to navigate much partition table. > > As to who concocted it, it was Microsoft and/or IBM. > > What uses this format natively? All the DOS family down to Windows 2000|ME and > OS/2. And Linux. And the CP/M family. > > There is some dissension wrt extended partitions - MS keeps on introducing new > codes for partition types. Thanks for the summary. I think you're inaccurate in stating that it has nothing to do with the PC BIOS, however. Agreed, that wasn't the origin, but this whole issue has come to a head because of BIOS involvement. > Here are the partition types Linux fdisk recognises: > > [root@emu /root]# fdisk > Using /dev/hda as default device! > > Command (m for help): l > > 0 Empty c Win95 FAT32 (LB 64 Novell Netware a6 OpenBSD > 1 DOS 12-bit FAT e Win95 FAT16 (LB 65 Novell Netware a7 NEXTSTEP > 2 XENIX root f Win95 Extended 75 PC/IX b7 BSDI fs > 3 XENIX usr 11 Hidden DOS FAT1 80 Old MINIX b8 BSDI swap > 4 DOS 16-bit <32M 14 Hidden DOS FAT1 81 Linux/MINIX c7 Syrinx > 5 Extended 16 Hidden DOS FAT1 82 Linux swap db CP/M > 6 DOS 16-bit >=32 17 Hidden OS/2 HPF 83 Linux native e1 DOS access > 7 OS/2 HPFS 40 Venix 80286 85 Linux extended e3 DOS R/O > 8 AIX 41 PPC PReP Boot 93 Amoeba eb BeOS fs > 9 AIX bootable 51 Novell? 94 Amoeba BBT f2 DOS secondary > a OS/2 Boot Manag 52 Microport a5 BSD/386 ff BBT > b Win95 FAT32 63 GNU HURD > > Command (m for help): > > How many are used natively, and how many under sufferance, I do not know. > > Note: this table is not completely accurate: the OS/2 definition of 0x07 is > "installable filesystem." It's usually HPFS, but need not be. There are other inaccuracies. It calls the FreeBSD partition type "BSD/386", and it doesn't know NetBSD (169/0xa9) and BSDi (forgotten which number). I've been meaning to submit patches for a while. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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