df (disk free space) in Linux CLI - Commands & Configuration

Introduction

Sometimes your computer's storage gets full and you need to check how much space is left. The df command shows you the free and used disk space on your drives so you can manage your files better.

When you want to see how much space is left on your hard drive before saving large files.

When your computer warns you about low disk space and you want to find which drive is full.

When you are cleaning up files and want to check if deleting files freed enough space.

When you want to monitor disk usage on a server to avoid running out of space.

When you want to check the size of mounted drives like USB sticks or external disks.

Commands

This command shows disk space usage for all mounted filesystems in blocks. It gives a quick overview of used and available space.

Terminal

df

Expected Output

Filesystem     1K-blocks    Used Available Use% Mounted on

/dev/sda1      20511356 12345678   7156678  64% /

This command shows disk space usage in a human-readable format, using KB, MB, or GB so it's easier to understand.

Terminal

df -h

Expected Output

Filesystem      Size  Used Avail Use% Mounted on

/dev/sda1        20G   12G  6.8G  64% /

→

-h - Show sizes in human-readable format (KB, MB, GB)

This command adds the type of filesystem (like ext4 or tmpfs) to the output, helping you know what kind of storage is used.

Terminal

df -T

Expected Output

Filesystem     Type     1K-blocks    Used Available Use% Mounted on

/dev/sda1      ext4     20511356 12345678   7156678  64% /

→

-T - Display filesystem type

This command shows disk usage only for the /home directory, useful when you want to check space on a specific folder's drive.

Terminal

df -h /home

Expected Output

Filesystem      Size  Used Avail Use% Mounted on

/dev/sda2        50G   30G   18G  63% /home

Key Concept

If you remember nothing else from this pattern, remember: df shows how much disk space is used and free on your drives so you can manage storage.

Common Mistakes

Running df without -h and expecting easy-to-read sizes

The output shows sizes in blocks which are hard to understand quickly.

Use df -h to see sizes in KB, MB, or GB for easier reading.

Using df on a directory without knowing it shows the filesystem containing that directory

You might think it shows only that folder's size, but it shows the whole drive's usage.

Understand df reports disk usage per filesystem, not per folder size.

Summary

Use df to check disk space usage on all mounted filesystems.

Add -h flag to see sizes in human-readable format like MB or GB.

Use -T flag to see the type of filesystem for each mount point.

You can specify a directory to see disk usage for its filesystem only.