$ Linux Command

Disk

fdisk

View and edit disk partition tables.

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Additional Notes

fdisk is a disk command used to view and edit partition tables on a block device. It creates, deletes, and resizes partitions, and writes the Master Boot Record (MBR) or GUID Partition Table (GPT) metadata.

fdisk is interactive: you start it on a device such as /dev/sda, then issue single-letter commands. For GPT disks, gdisk or parted are often preferred, but fdisk supports GPT too on modern systems.

Syntax

fdisk [options] DEVICE

Parameters

  • options: Flags that change how fdisk behaves.
  • DEVICE: The block device to inspect or modify, such as /dev/sda.

Common Options

  • -l, --list: List partition tables of all or named devices.
  • -l DEVICE: Show the partition table for a specific device.
  • -u=cylinders / -u=sectors: Set the display unit (sectors is default).
  • -b SECTOR-SIZE: Override sector size when reading a disk image.

Interactive Commands

Inside fdisk DEVICE:

  • p: Print the current partition table.
  • n: Create a new partition.
  • d: Delete a partition.
  • t: Change a partition's type (for example 83 Linux, 82 swap).
  • a: Toggle the bootable flag (MBR).
  • m: Show the help of commands.
  • w: Write changes to disk and exit.
  • q: Quit without saving changes.
  • g: Create a new empty GPT table.
  • o: Create a new empty DOS/MBR table.

Examples

sudo fdisk -l

List every disk and its partitions.

sudo fdisk -l /dev/sdb

Show the partition table of /dev/sdb only.

sudo fdisk /dev/sdb

Open an interactive session on /dev/sdb, then use p, n, d, and w.

Command (m for help): p
Command (m for help): n
Partition type: p
Partition number: 1
First sector: (default)
Last sector: +20G
Command (m for help): w

Create a 20 GB primary partition and write it to disk.

Practical Notes

  • Always run fdisk -l first and back up important data before editing.
  • w writes changes immediately; q discards them.
  • After creating partitions, format them with mkfs (such as mkfs.ext4) before use.
  • Use partrobe after changes so the kernel reloads the partition table.
  • For GPT management with more features, consider gdisk or parted.