Re: Linux and Windows partitioners fail to see opposite partitions
On Wed, 24 Mar 2010 14:01:19 -0400 (EDT), Elmer E. Dow wrote:
>
> It's sinking in now that evidently the mbr and the partition table are the
> same thing.
The master boot record is cylinder 0, head 0, record 1, the very first
record on the hard disk, which is outside of any partition. The master
boot record *contains* the main partition table. According to the standard
MS-DOS partitioning scheme, one can define a minimum of 0, maximum of 4
primary partitions, a minimum of 0, maximum of 1 extended partitions, and
the total of primary partitions plus extended partitions is a minimum of
0, maximum of 4. Thus, if an extended partition is present, there can be
a maximum of three primary partitions. If an extended partition is not
present, there can be up to four primary partitions. Linux assigns the
partitions defined here a number in the range 1-4.
If an extended partition is defined, then the boot sector for the extended
partition (which is separate from the master boot record) *contains* the
definitions for the logical drives, which can be thought of as a secondary
partition table. (I'm using DOS terminology here.
DOS calls them "logical drives". Linux calls them "logical partitions".)
Linux assigns these logical partitions a number from 5 and up. There can be a
gap in partition numbers if an extended partition is defined and fewer than
three primary partitions are defined. For example, /dev/hda1 could be a
primary partition, /dev/hda2 could be an extended partition, /dev/hda3
does not exist, /dev/hda4 does not exist, and /dev/hda5 is a logical
partition. The extents defined for the extended partition in the main
partition table (starting cylinder and ending cylinder) must cover the
entire range of extents defined for all logical drives, and may overlap
on both sides. In other words, a logical partition is a sub-division of
the extended partition.
HTH
--
.''`. Stephen Powell <zlinuxman@wowway.com>
: :' :
`. `'`
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