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fdisk Command Cheat Sheet

fdisk is a menu-driven command-line utility for creating and manipulating partition tables on a hard disk. It understands GPT, MBR, Sun, SGI, and BSD partition tables.

Synopsis

fdisk [options] device
fdisk -l [device...]

Basic Usage

List Partitions (-l)

List the partition tables of specific devices or all devices if none given.

sudo fdisk -l

Start Interactive Mode

Open a disk for editing.

sudo fdisk /dev/sdX
(Replace sdX with your drive, e.g., /dev/sdb. Do not use partition numbers like sdb1 unless resizing loop devices).

Interactive commands

Once inside fdisk, you use single-letter commands.

Command Description
m Display help menu
p Print the partition table
n Create a new partition
d Delete a partition
t Change partition type
l List known partition types
w Write changes to disk and exit
q Quit without saving changes
g Create a new empty GPT partition table
o Create a new empty DOS (MBR) partition table
v Verify the partition table

Common Tasks

1. Create a New Partition

  1. Run sudo fdisk /dev/sdb
  2. Type n (New)
  3. Select partition type (Primary p or Extended e) - MBR only
  4. Partition number (1-4)
  5. First sector (Press Enter for default)
  6. Last sector (Enter +size, e.g., +20G for 20GB)
  7. Type w to write changes.

2. Delete a Partition

  1. Type d
  2. Enter partition number (if multiple exist)
  3. Type w to save.

3. Change Partition Type (e.g., to Swap or LVM)

  1. Type t
  2. Enter partition number
  3. Enter hex code (Type L to see codes)
    • 82: Linux Swap
    • 83: Linux (default)
    • 8e: Linux LVM
    • ef: EFI System (GPT)
  4. Type w to save.

Scripting (Non-Interactive)

You can script fdisk by piping commands into it.

Create a Single Partition

echo -e "n\np\n1\n\n\nw" | sudo fdisk /dev/sdb
Sequence: New -> Primary -> 1 -> Default Start -> Default End -> Write.

Create a Specific Size Partition

# New partition of 5GB
sed -e 's/\s*\([\+0-9a-zA-Z]*\).*/\1/' << EOF | sudo fdisk /dev/sdb
n
p
1

+5G
w
EOF

Better Alternative: sfdisk

For scripting, sfdisk is generally preferred over hacking fdisk with echo.

echo ",,L" | sudo sfdisk /dev/sdb

MBR vs GPT

  • MBR (Master Boot Record): Legacy. Max 4 primary partitions (or 3 primary + 1 extended). Max 2TB disk size.
  • GPT (GUID Partition Table): Modern. Limitless partitions (128 by default). Supports disks > 2TB.

Convert to GPT: Inside fdisk, type g. Warning: This erases all data on the disk!

After Partitioning

Changes to the partition table are not always instantly visible to the kernel.

Reload Partition Table

sudo partprobe /dev/sdb
# OR
sudo kpartx -u /dev/sdb

Format the Partition

Once created, you must format it with a filesystem.

sudo mkfs.ext4 /dev/sdb1

Tips

  • Safety: Double-check the device name (lsblk) before opening fdisk.
  • Align: Modern fdisk automatically aligns partitions to physical sector boundaries (2048 sectors), which is crucial for SSD/RAID performance.
  • Resize: fdisk can resize partitions by deleting and recreating them with the SAME start sector and a larger end sector. (Risky, use gparted or resize2fs if possible).