Why fdisk and lsblk in Linux CLI? - Purpose & Use Cases

The Big Idea

What if a few simple commands could save your data and sanity when managing disks?

The Scenario

Imagine you just bought a new hard drive and want to use it on your Linux computer. You try to figure out its size, partitions, and how to set it up by opening multiple windows, guessing device names, and writing notes on paper.

The Problem

Doing this by hand is slow and confusing. You might mix up device names, miss important details, or accidentally delete data. Without clear commands, it's easy to make mistakes that can cause data loss or system problems.

The Solution

Using fdisk and lsblk commands lets you quickly see all disks and partitions, and safely create or modify partitions. They give clear, organized information and simple interactive tools to manage disks without guesswork.

Before vs After

✗ Before

cat /proc/partitions
ls /dev/sd*
# guess which device is new

✓ After

lsblk
fdisk -l
# see all disks and partitions clearly

What It Enables

You can confidently manage disk partitions and storage devices, making your system setup faster, safer, and less stressful.

Real Life Example

When installing a new Linux system, you use lsblk to list all drives and fdisk to create partitions for system, swap, and data, ensuring everything is correctly set up before installation.

Key Takeaways

Manual disk management is confusing and risky.

fdisk and lsblk provide clear, safe ways to view and edit disk partitions.

They save time and prevent costly mistakes when handling storage devices.

Practice

1. What is the primary purpose of the fdisk command in Linux?

easy

A. To display the current directory contents

B. To create and modify disk partitions

C. To list running processes

D. To monitor network connections

Solution

1. Step 1: Understand the role of fdisk

   The fdisk command is used to create, delete, and modify disk partitions on Linux systems.

2. Step 2: Compare with other commands

   Other options like listing directories, processes, or network connections are unrelated to disk partitioning.

3. Final Answer:

   To create and modify disk partitions -> Option B

4. Quick Check:

   fdisk = disk partition tool [OK]

Hint: fdisk = fix disk partitions [OK]

Common Mistakes:

• Confusing fdisk with lsblk
• Thinking fdisk lists files
• Assuming fdisk monitors network

2. Which of the following is the correct syntax to list all block devices using lsblk?

easy

A. lsblk --all

B. lsblk -d

C. lsblk -l

D. lsblk -f

Solution

1. Step 1: Identify the option to list all devices

   The --all option with lsblk lists all devices, including empty ones.

2. Step 2: Check other options

   -d lists only whole disks (no partitions), -l lists in list format, -f shows filesystem info but not all devices.

3. Final Answer:

   lsblk --all -> Option A

4. Quick Check:

   lsblk --all = show all devices [OK]

Hint: --all shows everything in lsblk [OK]

Common Mistakes:

• Using -d instead of --all
• Confusing -l with --all
• Using -f to list devices

3. Given the command output below, what is the size of the partition /dev/sda1?

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  100G  0 disk 
sda1     8:1    0   50G  0 part /
sda2     8:2    0   50G  0 part /home

medium

A. 100G

B. 0G

C. 50G

D. 150G

Solution

1. Step 1: Read the lsblk output

   The line for /dev/sda1 shows a size of 50G under the SIZE column.

2. Step 2: Understand partition sizes

   The disk sda is 100G total, split into two partitions of 50G each.

3. Final Answer:

   50G -> Option C

4. Quick Check:

   /dev/sda1 size = 50G [OK]

Hint: Check SIZE column for partition size [OK]

Common Mistakes:

• Confusing disk size with partition size
• Adding partition sizes incorrectly
• Ignoring the SIZE column

4. You run fdisk /dev/sdb but get the error: cannot open /dev/sdb: Permission denied. What is the most likely cause?

medium

A. The disk /dev/sdb is formatted with ext4

B. The disk /dev/sdb is already mounted

C. The lsblk command is not installed

D. You forgot to run the command as root or with sudo

Solution

1. Step 1: Understand permission requirements

   Running fdisk on disks requires root privileges; without sudo or root, device access is denied.

2. Step 2: Check other options

   Disk being mounted or formatted does not cause 'Permission denied' error; missing lsblk is unrelated.

3. Final Answer:

   You forgot to run the command as root or with sudo -> Option D

4. Quick Check:

   fdisk needs root access [OK]

Hint: Use sudo with fdisk to access disks [OK]

Common Mistakes:

• Assuming mounted disk causes 'Permission denied'
• Thinking formatting affects fdisk detection
• Confusing fdisk errors with lsblk issues

5. You want to create a new partition on /dev/sdc using fdisk. After creating the partition, which command should you run to immediately see the updated partition layout in a tree view?

hard

A. lsblk /dev/sdc

B. fdisk -l /dev/sdc

C. mount /dev/sdc1 /mnt

D. df -h /dev/sdc

Solution

1. Step 1: Identify command to show partition tree

   lsblk displays block devices and partitions in a clear tree format, perfect for checking new partitions.

2. Step 2: Compare with other commands

   fdisk -l lists partitions but not in tree view; mount mounts partitions; df -h shows disk usage, not layout.

3. Final Answer:

   lsblk /dev/sdc -> Option A

4. Quick Check:

   lsblk shows partition tree [OK]

Hint: Use lsblk to view partitions visually [OK]

Common Mistakes:

• Using fdisk -l expecting tree view
• Trying to mount before checking partitions
• Using df to see partition layout