The Power of df

In the realm of Linux system administration, disk space management is a critical task. Among the many tools available, the df command stands out as one of the most fundamental and widely used utilities. This article explores the power of the df command, highlights its most interesting options, and compares it with alternatives like dust.

Understanding the "df" Command

The df (disk free) command in Linux provides a concise overview of the disk space usage on your file systems. By default, it displays the total, used, and available space on all mounted file systems.

Basic Usage

To get a quick summary of disk usage, simply type:

df

This command will output something like:

Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sda1       41151820  1205408  37785112   4% /
tmpfs            2010928        0   2010928   0% /dev/shm

Common Options

The df command comes with several options that enhance its functionality:

Human-readable format: Adding the -h flag provides a more readable output by displaying sizes in human-friendly units (KB, MB, GB).

df -h

Output

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        40G  1.2G   36G   4% /
tmpfs           2.0G     0  2.0G   0% /dev/shm

Include filesystem type: The -T option adds a column to show the type of each file system.

df -T

Output

Filesystem     Type     1K-blocks     Used Available Use% Mounted on
/dev/sda1      ext4      41151820  1205408  37785112   4% /
tmpfs          tmpfs      2010928        0   2010928   0% /dev/shm

Inodes usage: If you are concerned about inode usage, which can be crucial for file-heavy systems, the -i option will display the number of inodes used and available.

df -i

Filesystem     Inodes  IUsed   IFree IUse% Mounted on
/dev/sda1     2621440  56384 2565056    3% /
tmpfs          502732      1  502731    1% /dev/shm

Interesting Commands

Combining df with other command-line utilities can yield powerful insights:

Monitoring disk usage over time: You can create a simple script to monitor disk usage periodically and log the results.

while true; do df -h >> disk_usage.log; sleep 60; done

Filtering specific file systems:

To filter the output to only include specific file systems, use the grep command.

df -h | grep "^/dev"

Displaying Disk Usage in Different Block Sizes

You can use the -B option to display disk usage in different block sizes, such as bytes, kilobytes, megabytes, or gigabytes.

df -B1     # Display in bytes
df -BK     # Display in kilobytes
df -BM     # Display in megabytes
df -BG     # Display in gigabytes

However -h seems more memorable to me.

Displaying Disk Usage for a Specific File System

df -h /home

Alerting on Low Disk Space

if [ $(df / | awk 'NR==2 {print $5}' | sed 's/%//') -gt 90 ]; then
echo "Disk space is critically low!" | mail -s "Disk Space Alert" your_email@example.com
fi

Alternatives to "df"

While df is robust and widely used, there are alternatives like dust that offer enhanced features and more user-friendly outputs.

Dust

dust is a Rust-based disk usage tool that provides an intuitive visualization of disk usage, making it easier to spot large files and directories.

Installation

You can install dust via cargo, Rust's package manager:

cargo install du-dust

Usage

The basic usage of dust is simple:

dust

This command provides a more visual and hierarchical view of disk usage, showing a tree structure with the largest directories first.

Comparison with "df"

• Visual Representation:df provides a tabular view of disk usage, while dust offers a more graphical and hierarchical representation, making it easier to identify which directories are consuming the most space.
• Ease of Use:dust is designed to be more user-friendly and visually appealing, especially for users who prefer a quick glance at their disk usage.
• Additional Features:dust includes additional features like interactive modes and the ability to exclude specific directories, which are not available in df.

Dust vs df

1. Basic Disk Usage:df: Provides basic disk usage information for all mounted file systems.
   dust: Offers a comprehensive view of disk usage, emphasizing large files and directories.
   
2. Human-readable Output:df: Supports human-readable output with the -h option.
   dust: Displays human-readable output by default.
   
3. File System Type Information:df: Can display the type of each file system with the -T option.
   dust: Does not provide file system type information.
   
4. Inode Information:df: Displays inode usage with the -i option.
   dust: Does not provide inode information.
   
5. Visual Output:df: Displays data in a tabular format.
   dust: Provides a graphical and hierarchical representation of disk usage, with color coding.
   
6. Interactive Mode:df: No interactive mode.
   dust: Includes an interactive mode to explore disk usage.
   
7. Directory Exclusion:df: Does not support excluding specific directories from the output.
   dust: Allows excluding specific directories to refine the disk usage view.
   

By understanding these differences, you can choose the right tool for your specific needs in disk space management on Linux systems.

Conclusion

The df command remains a powerful and essential tool for Linux users, providing detailed information about disk space usage. Its versatility with various options and the ability to combine with other commands make it a go-to utility for many system administrators. However, alternatives like dust offer enhanced visualization and ease of use, making them valuable additions to the toolbox of any Linux user. Understanding and utilizing both df and its alternatives will ensure efficient and effective disk space management on your Linux systems.