How to Use df Command in Linux: Syntax and Examples

Use the df command in Linux to display disk space usage of file systems. Running df -h shows human-readable sizes for easier understanding. This command helps monitor available and used disk space quickly.

Syntax

The basic syntax of the df command is:

• df [options] [file]

Here, options modify the output format, and file is an optional path to check the disk usage of the file system containing that file.

Common options include:

• -h: Show sizes in human-readable format (e.g., 1K, 234M, 2G).
• -T: Display the file system type.
• -a: Include all file systems, even dummy ones.

bash

df [options] [file]

Example

This example shows how to use df -h to display disk usage in a readable format:

bash

df -h

Output

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        50G   20G   28G  42% /
tmpfs           1.9G     0  1.9G   0% /dev/shm
/dev/sdb1       100G   60G   35G  64% /data

Common Pitfalls

Some common mistakes when using df include:

• Not using -h option, which makes sizes hard to read as they are in blocks.
• Confusing df output with du, which shows directory sizes, not disk usage.
• Expecting df to show free space on specific files instead of file systems.

Wrong usage example:

df /home/user/file.txt

This shows the file system containing the file, not the file size.

Right usage to check disk space:

df -h

bash

df /home/user/file.txt
df -h

Output

/dev/sda1        50G   20G   28G  42% /
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        50G   20G   28G  42% /

Quick Reference

Option	Description
-h	Show sizes in human-readable format
-T	Display file system type
-a	Include all file systems
-i	Show inode usage instead of block usage
[file]	Show disk usage of the file system containing this file

Key Takeaways

Use df -h to see disk space in easy-to-read sizes.

The df command shows file system usage, not individual file sizes.

Common mistake: forgetting -h makes output hard to understand.

Use options like -T to get more details about file systems.

Check disk space regularly to avoid running out of storage.