Partitioning divides a disk drive into one or more logical disks. Each partition is treated as a separate disk with its own file system. Partition information is stored in a partition table.
Primary vs Extended partitions
The original partitioning scheme for PC hard disks allowed only four partitions, called primary partitions. To create more than four partitions, one of these four partitions can be divided into many smaller partitions, called logical partitions. When a primary partition is subdivided in this way, it is known as an extended partition. The partitioning tools presented in this lesson allow you to create primary or extended partitions.
How to list disk partitions
Partition devices are listed in the /proc/partitions file:
# cat /proc/partitions major minor #blocks name 8 16 20971520 sdb 8 0 20971520 sda ...
The columns are described as follows:
major: The major number of the device. This corresponds with the block device in the
/proc/devices file.
minor: The minor number of the device. This relates to the number at the end of the partition name.
#blocks: The number of physical disk blocks contained in the partition.
name: The name of the partition.
Various utilities are available to display and manipulate the partition table.
1. fdisk
2. cfdisk
3. parted
fdisk utility
The fdisk utility is a common partition table manipulator for Linux. Use fdisk –l to list the partition table. To display the partition for a specific device, include the device name as an argument. For example:
# fdisk -l /dev/sda Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk label type: dos Disk identifier: 0x000dddc2 Device Boot Start End Blocks Id System /dev/sda1 * 2048 2099199 1048576 83 Linux /dev/sda2 2099200 41943039 19921920 8e Linux LVM
cfdisk utility
The screenshot in the picture below shows the user interface of the cfdisk utility, which is used to create, delete, and modify partitions on a disk device. Enter the cfdisk command and include the device that you want to partition as an argument.
# cfdisk /dev/sda
parted utility
The GNU parted utility is also used to view the existing partition table, change the size of existing partitions, or add partitions from free space or additional hard drives. This utility is more advanced than the fdisk utility. It supports more disk label types and offers additional commands. To view partitions in the disk, use the print subcommand in parted utility:
# parted /dev/sda GNU Parted 3.1 Using /dev/sda Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) print Model: VMware, VMware Virtual S (scsi) Disk /dev/sda: 21.5GB Sector size (logical/physical): 512B/512B Partition Table: msdos Disk Flags: Number Start End Size Type File system Flags 1 1049kB 1075MB 1074MB primary xfs boot 2 1075MB 21.5GB 20.4GB primary lvm (parted) quit