Partitioning Disks by Using fdisk

To create and manage hard disks that use MBRs, use the fdisk command. Or, you can use the cfdisk utility, which is a text-based, graphical version of fdisk.

Before running fdisk, complete the following requirements first:

  • Unmount any mounted partition on the disk.

  • Disable any partition that's being used as swap space by using the swapoff command.

  • Backup the data on the disk to be configured.

fdisk can be used either interactively or directly with command line options and arguments.

Note:

The two modes can differ in the options they support to perform specific actions. To list supported options while in interactive mode, enter m at the mode's prompt. For supported options in the command line mode, type: 

fdisk -h

To run the fdisk command interactively, specify only the name of the disk device as an argument, for example: 

sudo fdisk /dev/sda
Welcome to fdisk (util-linux 2.40.2)
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help):

The following commands are useful for managing partitions:

p

Displays the current partition table.

n

Initiates the process for creating new partitions.

t

Changes the partition type.

Tip:

To list all the supported partition types, enter l.

w

Commits changes you made to the partition table, then exits the interactive session.

q

Disregards any configuration changes you made and exits the session.

m

Displays all the supported commands in the interactive mode.

For more information, see the cfdisk(8) and fdisk(8) manual pages.

Displaying the Partition Table

To display the partition table, enter p at the fdisk prompt, for example: 

Command (m for help): p
Disk /dev/sda: 36.5 GiB, 39191576576 bytes, 76546048 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
Disklabel type: dos
Disk identifier: 0x67fb0c7a

Device     Boot   Start      End  Sectors  Size Id Type
/dev/sda1  *       2048  1026047  1024000  500M 83 Linux
/dev/sda2       1026048 76546047 75520000   36G 8e Linux LVM

Command (m for help):

The output contains device information summary such as disk size, disklabel type, and partition details. The partition details are specified under the following field names:

Device

Lists the current partitions on the device.

Boot

Identifies the boot partition with an asterisk (*). This partition contains the files that the GRUB bootloader needs to boot the system. Only one partition can be bootable.

Start and End

Lists the start and end offsets in sectors that mark a sector's boundaries. All partitions are aligned on one-megabyte boundaries.

Sectors

Displays sector sizes.

Size

Displays partition sizes.

Id and Type

Indicates a representative number and its corresponding representative number.

Oracle Linux typically supports the following types:

5 Extended

An extended partition that can contain up to four logical partitions.

82 Linux swap

Swap space partition.

83 Linux

Linux partition for a file system that's not managed by LVM. This is the default partition type.

8e Linux LVM

Linux partition that's managed by LVM.

Creating Partitions

The following example shows how to use the different fdisk interactive commands to partition a disk. 2 partitions are created on /dev/sdb. The first partition is assigned 2 GB while the second partition uses all the remaining disk space. 

sudo fdisk /dev/sdb

The command runs a menu-based system where you must select the appropriate responses to configure the partition. Example inputs are displayed in the following interactive session:

...
Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-32767999, default 2048): <Enter>
Last sector, +sectors or +size{K,M,G,T,P} (2048-32767999, default 32767999): +2G

Created a new partition 1 of type 'Linux' and of size 2 GiB.

Command (m for help): n
Partition type
   p   primary (1 primary, 0 extended, 3 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (2-4, default 2): 2
First sector (4196352-32767999, default 4196352): <Enter>
Last sector, +sectors or +size{K,M,G,T,P} (4196352-32767999, default 32767999): <Enter>

Created a new partition 2 of type 'Linux' and of size 13.6 GiB.

Command (m for help): p
Disk /dev/sdb: 15.6 GiB, 16777216000 bytes, 32768000 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
Disklabel type: dos
Disk identifier: 0x460247f0

Device     Boot   Start      End   Sectors   Size Id Type
/dev/sdb1          2048    4196351  4194304     2G 83 Linux
/dev/sdb2          4196352 32767999 28571648 13.6G 83 Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.