Cheatsheet & Examples: df

Basic Disk Usage Report

Example Usage: df

What it does: Displays the amount of disk space used and available on all mounted filesystems, using default units (blocks) and summarizing the data.

Command-line Arguments Explained:

• None: No arguments provided, so df defaults to showing disk usage for all filesystems in blocks.

Human-Readable Disk Usage

Example Usage: df -h

What it does: Shows disk usage in a human-readable format, using units like KB, MB, and GB instead of raw block counts.

Command-line Arguments Explained:

• -h: Enables human-readable output, converting block sizes to easily understandable units.

Show All Filesystems

Example Usage: df -a

What it does: Displays disk usage for all filesystems, including virtual ones like tmpfs or proc, which are usually excluded by default.

Command-line Arguments Explained:

• -a: Includes all filesystems in the output, even those that are typically not shown (e.g., virtual or special-purpose filesystems).

Disk Usage in Specific Units

Example Usage: df -k or df -m

What it does: Displays disk usage in kilobytes (-k) or megabytes (-m) instead of the default block size.

Command-line Arguments Explained:

• -k: Uses kilobytes as the unit for display.
• -m: Uses megabytes as the unit for display.

Filter by Filesystem Type

Example Usage: df -t ext4

What it does: Shows disk usage information only for filesystems of the specified type (e.g., ext4).

Command-line Arguments Explained:

• -t: Filters the output to display only filesystems of the given type (e.g., ext4, xfs, ntfs).

Exclude Specific Filesystem Types

Example Usage: df --exclude-type=tmpfs

What it does: Excludes filesystems of the specified type (e.g., tmpfs) from the disk usage report.

Command-line Arguments Explained:

• --exclude-type: Filters out filesystems of the given type from the output.

Inode Usage Statistics

Example Usage: df -i

What it does: Displays information about inode usage rather than block usage, showing how many inodes are used and available.

Command-line Arguments Explained:

• -i: Shows inodes (file metadata) usage instead of disk space usage.

Custom Output Fields

Example Usage: df --output=source,fstype,size,used,avail

What it does: Customizes the output to show specific fields (e.g., device source, filesystem type, size, used space, available space).

Command-line Arguments Explained:

• --output: Specifies which fields to display in the output. Available fields include source, fstype, size, used, avail, capacity, mountpoint, and more.

Disk Usage Summary

Example Usage: df --summarize

What it does: Provides a summary line at the end of the output, showing the total used and available space across all mounted filesystems.

Command-line Arguments Explained:

• --summarize: Adds a summary line to the output, summarizing disk usage for all filesystems.

Disk Usage with Specified Block Size

Example Usage: df --block-size=1M

What it does: Displays disk usage in the specified block size (e.g., megabytes) instead of the default.

Command-line Arguments Explained:

• --block-size: Sets the block size for display. Valid values include 1K, 1M, 1G (kilobytes, megabytes, gigabytes), or any numeric multiplier.

Help and Usage Instructions

Example Usage: df --help

What it does: Displays a help message with usage instructions and available options for the df command.

Command-line Arguments Explained:

• --help: Shows a summary of how to use df and lists its available options.

Version Information

Example Usage: df --version

What it does: Outputs the version of the df utility installed on the system.

Command-line Arguments Explained:

• --version: Displays the version number of df, confirming the implementation (GNU coreutils, macOS, etc.).