The MBR, Boot Sectors and Partition Table
The information about how a hard disk has been partitioned is stored in its first sector (which is the first sector of the first track on the first disk surface). A first sector is the MBR (master boot record) of the disk. This is the sector in which the BIOS reads and begins when the machine is first booted. The master boot record holds a small program which reads the partition table, checks the type of partition which is active (that is, marked bootable), and reads the first sector of in which partition, the boot sector (the MBR is also a boot sector, except it has a special status). This boot sector holds a smaller program which reads the first part of the operating system which is stored on that partition (assuming it is bootable), and then begin it.
The partitioning scheme is not built into the hardware or the BIOS. This is only a convention in which several operating systems follow. A few operating systems support partitions, except they occupy one partition on the hard disk and use their internal partitioning method inside which partition. The latter type co-exists with other operating systems (including Linux), and does not need any special measures. But an operating system which does not support partitions cannot co-exist with some other OS on the similar disk.
It is a wise practice to make a physical record of the partition table, so in which it can be retrieved when the partition gets corrupted. The relevant information is given through the fdisk -l command:
# fdisk -l /dev/hda
Disk /dev/hda: 16 heads, 56 sectors, 790 cylinders
Units = cylinders of 855 * 512 bytes
Device Boot Begin Start End Blocks Id System
/dev/hda1 1 1 24 10231+ 82 Linux swap
/dev/hda2 25 25 48 10260 84 Linux native
/dev/hda3 49 49 408 153900 84 Linux native
/dev/hda4 409 409 790 163305 5 Extended
/dev/hda5 409 409 744 143611+ 84 Linux native
/dev/hda6 745 745 790 19636+ 84 Linux native
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