How to Use fdisk Command in Linux: Syntax and Examples

The fdisk command in Linux is used to create, delete, and manage disk partitions interactively. Run sudo fdisk /dev/sdX (replace /dev/sdX with your disk) to enter the fdisk menu where you can use commands like n to create a new partition and w to save changes.

Syntax

The basic syntax of the fdisk command is:

• sudo fdisk [options] device

Here:

• sudo runs the command with administrator rights needed for disk changes.
• fdisk is the command itself.
• device is the disk you want to manage, like /dev/sda or /dev/sdb.

Inside the interactive menu, you use single-letter commands like m for help, p to print the partition table, n to add a new partition, and w to write changes.

bash

sudo fdisk /dev/sdX

Example

This example shows how to create a new partition on disk /dev/sdb using fdisk. It demonstrates entering fdisk, listing partitions, creating a new one, and saving changes.

bash

sudo fdisk /dev/sdb

# Inside fdisk interactive prompt:
# Command (m for help): p
# (prints current partitions)
# Command (m for help): n
# Partition type
#   p   primary (0 primary, 0 extended, 4 free)
#   e   extended
# Select (default p): p
# Partition number (1-4, default 1): 1
# First sector (2048-..., default 2048): (press Enter)
# Last sector, +sectors or +size{K,M,G,T,P} (2048-..., default ...): +1G
# Command (m for help): w
# (writes changes and exits)

Output

Disk /dev/sdb: 10 GiB, 10737418240 bytes, 20971520 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x12345678

Device     Boot Start     End Sectors  Size Id Type
/dev/sdb1        2048  2099199 2097152    1G 83 Linux

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Common Pitfalls

Common mistakes when using fdisk include:

• Not running fdisk with sudo, causing permission errors.
• Choosing the wrong disk device, which can lead to data loss.
• Forgetting to write changes with w, so no changes are saved.
• Not backing up data before modifying partitions.

Always double-check the disk device and backup important data before using fdisk.

bash

sudo fdisk /dev/sda
# User forgets to type 'w' and exits with 'q'
# No changes are saved

# Correct way:
# After making changes, type 'w' to save and exit

Quick Reference

Command	Description
m	Show help menu with all commands
p	Print current partition table
n	Create a new partition
d	Delete a partition
t	Change a partition's type
w	Write changes to disk and exit
q	Quit without saving changes

Key Takeaways

Always run fdisk with sudo to have the necessary permissions.

Use fdisk interactively to create, delete, or modify disk partitions safely.

Double-check the disk device name before making changes to avoid data loss.

Remember to write changes with the 'w' command to apply them.

Back up important data before modifying partitions with fdisk.