# fdisk -l
Disk /dev/hda: 240 heads, 63 sectors, 1940 cylinders
Units = cylinders of 15120 * 512 bytes
Device Boot Start End Blocks Id System
/dev/hda 1 286 2162128+ c Win95 FAT32 (LBA)
/dev/hda2 * 288 1940 12496680 5 Extended
/dev/hda5 288 289 15088+ 83 Linux
/dev/hda6 290 844 4195768+ 83 Linux
/dev/hda7 845 983 1050808+ 82 Linux swap
/dev/hda8 984 1816 6297448+ 83 Linux
/dev/hda9 1817 1940 937408+ 83 Linux
The nomenclature /dev/hda to /dev/hdd in the partition table refers to IDE drives 1 through 5, with hda referring to drive 1, hdb referring to drive 2, and so on. Partitions within a drive are referred to by number, so that /dev/hda5 would be the fifth partition on the first IDE drive. For SCSI drives, a similar naming scheme is used: /dev/sda to /dev/sdd.
Partitions No. 1 through 4 are reserved for primary partitions, and 5 and up are used for logical partitions. So, for the partition tables shown above, there is one drive, hda, with one primary partition, hda1, and one extended partition, hda2, with five logical partitions, /dev/hda5 through /dev/hda9. The filesystem listed as shmfs represents the shared memory filesystem mounted as a special filesystem according to POSIX standards in Linux 2.4.
You may have noticed the LBA in parentheses in the fdisk listing. LBA stands for logical block addressing, which converts the cylinder, block, and sector schema of a hard disk into linear block numbers for processing.
In Linux, partitions are either primary, extended, or logical partitions. The term primary partition is a holdover from the limitation of four partitions on old x86 systems. Unlike DOS and Windows, Linux can boot from a primary or a logical partition. Primary partitions that serve as placeholders for logical partitions are referred to as extended partitions. An extended partition has its own partition table that points to one or more logical partitions, which are simply subdivisions of a primary partition. In the fdisk listing above, hda2 is an extended partition.