Hard Drives and MBR Post: 302816363

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Special Forums Hardware Hard Drives and MBR Post 302816363 by Corona688 on Monday 3rd of June 2013 05:27:33 PM

06-03-2013

Registered User

I'll explain this first: A hard drive doesn't know or care what its contents are. If it gives you sector 123523 when you ask for 123523, it has fulfilled its responsibility.

You don't "install" an MBR, it's just there, in sector zero, because that's where your computer expects it to be by tradition. If sector zero doesn't have valid contents, your computer just won't boot from it. More modern things like GPT -- which can have partitions much larger than a basic DOS-style MBR would support -- have extra data elsewhere as well, at the end of the disk I believe...

You don't get to put partitions in the first 63 sectors just because that's how DOS-style partition tables work, they can't represent numbers any lower than that.

Some disks will come formatted with a sensible MBR. Some just fill it with zeroes. It doesn't matter much, since there's no barrier to doing what you please with it.

The only thing actually stopping you from writing over the MBR is the operating system. When you partition a device in Linux, it breaks it out into separate pretend-devices like /dev/sda1, /dev/sda2, and so forth. Theyr'e safely compartmentalized, they won't let you write beyond their bounds, but it's the OS doing that for your convenience, not the disk itself. You can use /dev/sda itself if you want to talk to the raw device, but almost nothing except a partition editor would need to do so.

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LEARN ABOUT DEBIAN

acorn-fdisk

FDISK(8)						    BSD System Manager's Manual 						  FDISK(8)

NAME

     acorn-fdisk -- partition editor for Acorn/RISC OS machines

SYNOPSIS

     acorn-fdisk -h | --help | -v | --version

     acorn-fdisk [-t scheme | --type scheme] -l | --list [device ...]

     acorn-fdisk [-t scheme | --type scheme] -s | --size partition

     acorn-fdisk [-t scheme | --type scheme] [device]

DESCRIPTION

     The acorn-fdisk utility allows one to display or interactively edit partition tables for Acorn/RISC OS machines in various formats.  Using
     the PC/BIOS format, standard IBM PC (i386) partition tables can also be accessed.	When no optional device is given, it defaults to /dev/hda
     or /dev/sda.

     The options are as follows:

     -h | --help  Display a short usage and exit immediately.

     -l | --list  Display the partition table(s) of all devices.

     -s | --size  Display the size of partition.

     -t | --type  Select the partitioning scheme to use.  Valid schemes are:

		  EESOX 	   Eesox SCSI on the Acorn machines.

		  ICSIDEFS	   ICS IDE.

		  Filecore/Linux   Linux on Filecore.  This uses the non-ADFS descriptor to point to the start of the disc to be partitioned.  The
				   first two sectors contain a partition table to identify the Linux partitions contained within.

		  PC/BIOS	   PC/BIOS partitioning scheme.  This consists of a partition table in the first sector of the disk which contains
				   both CHS and LBA values for the partitions.	There can be up to four entries in the primary partition table.
				   One of these can be an extended partition containing up to four extra partitions.

		  PowerTec	   PowerTec SCSI on the Acorn machines.

		  Filecore/RISCiX  RiscIX on Filecore.

     -v | --version
		  Display the version of acorn-fdisk and exit immediately.

     If neither -l | --list or -s | --size are given, the partition table of the given device will be edited interactively.

EXAMPLES

     Display the default device's partition table on a PC:

	   acorn-fdisk --type PC/BIOS -l

     Display the PC partition table of /dev/sda:

	   acorn-fdisk --type PC/BIOS --list /dev/sda

     Display the size in blocks of the partition /dev/sda1:

	   acorn-fdisk --type PC/BIOS --size /dev/sda1

     Edit the MBR partition table interactively:

	   acorn-fdisk --type PC/BIOS

     Display the partition table of an MBR backed up to a file:

	   acorn-fdisk -t PC/BIOS -l mbrdump.bin

     Display the size of the first partition on a device where the MBR would be restored from the backup file mbrdump.bin:

	   acorn-fdisk -t PC/BIOS -s mbrdump.bin1

AUTHORS

     arm-fdisk was written by Russell King <rmk@arm.uk.linux.org> based on util-linux fdisk, which was written at least partially by
     A. V. Le Blanc <LeBlanc@mcc.ac.uk>.

     This manual page was written for the Debian system by
     Thorsten Glaser <tg@debian.org> but may be used by others.

BSD
								  October 2, 2010							       BSD

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