A partition is a logical section of a hard disk and a practical way for users to divide their disks up into parts that behave as independent, separate devices, which in reality reside on one hard disk. A partition is technically defined in the partition table of a hard disk.
- 1 Why partition?
- 2 Partition Topology
- 3 Practical
- 4 See also
Partitioning has several advantages and disadvantages.
Most practically, partitioning allows you to set up different operating systems on a single disk. If you have successfully installed any multiple-boot system, say, with Linux, partitioning allows the different operating systems to coexist and not interfere.
Managing hard disk space
Partitioning also alleviates the problem of managing hard disk space, especially within a multi-user system. For example, when a multi-user system is set up, the home directories and the system directories often reside on different partitions. Without partitioning the disk in this way, or without setting up adequate disk quota systems, a user can fill up the partition and render the system unusable. Separating respective directories by usage into partitions can assist in alleviating space issues.
Problems with partitioning
Partitioning a disk is a rather low-level operation, and if it fails, valuable data can get lost. Performing partitioning requires a high grade of technical proficiency and accuracy without the use of the right tools.
Types of partitions
As for types of partitions we know "Primary", "Extended" and "Logical" partitions. The basic types are Primary and Logical, where Extended appears as a special case of a Primary partition. A disk can only have maximum 4 Primary but never more than 1 Extended partition. A certain amount of Logical partitions (also called "Logical Drives") can be defined within the Extended partition. Primary and Logical partitions are addressable for disk space whereas Extended is only a nominal entry in the partition-table representing the set of its Logical partitions.
Linux reserves hda1, hda2, hda3 and hda4 for the 4 primary partitions and the first logical partition always starts with hda5. Windows counts through all addressable partitions by drive letters starting from "C" (C,D,E,...).
In Windows the total number of partitions is limited by the 26 alphabets. Linux permits 63 partitions in an IDE disk but only 15 in an SCSI or Sata disk. Some operating system, as e.g. Windows, can only be booted from a Primary partition, Linux can be booted from either a Primary or a Logical partition.
How do I create partitions?
On Linux systems, partitions are managed by programs such as fdisk or cfdisk. It is very dangerous to repartition a running system, and any changes in partitioning can render the data on the affected areas of the disk unusable. You will almost never have to partition unless you are installing a new operating system, or a new hard drive.
What partitions do I need?
Read the Partitioning Guidelines for suggestions on how to divide up your available disk space.
How do I see the partitions on my computer?
fdisk -l /dev/hda
You can see all partitions (of all devices) known by the kernel with
You can print the filesystem types in use with:
Find out a partition's size
To find out a partition's size in bytes (or megabytes or what may come in the future), use fdisk. Using fdisk on a partition will not print you a partition table, obviously, but it will print you the partition's size like this:
fdisk -l /dev/sdc1 Disk /dev/sdc1: 80.0 GB, 80023716864 bytes 255 heads, 63 sectors/track, 9728 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System
In this example, we find out /dev/sdc1 has a size of 80.0 GB.