Disk Free (df) Command
The df command (short for "disk free") is a standard
Unix and Linux command-line utility that reports file system disk
space usage. It displays the amount of disk space used and available
on file systems. Understanding disk usage is crucial for system
administration, performance monitoring, and preventing
storage-related issues.
View Disk Space Usage
The primary function of the df command is to show how
much space is used and available on your mounted file systems. This
helps in identifying which partitions or drives are running low on
space.
Human-Readable Disk Space
To make the output easier to read, you can use the
-h option. This displays sizes in powers of 1024 (e.g.,
KB, MB, GB).
# df -h
# Report file system disk space usage in a human-readable format.
df -h
Filter by File System Type
You can filter the output to show only specific file system types
using the -t option, or exclude certain types with the
-x option.
# Free disk space for [t]ype EXT2 file systems.
df -t ext2
# Free disk space for filesystems, e[x]cluding EXT2.
df -x ext2
Check Inode Usage
Besides block usage, it's also important to monitor inode usage.
Inodes are data structures that store information about files and
directories. Running out of inodes can prevent new files from being
created, even if there's free disk space. Use the
-i option to view inode usage.
# Show [i]node usage.
df -i
Display Specific File System Information
To get information about a particular file system or mount point, specify the path.
# Show information about a distinct filesystem path.
df [PATH]
Show All File Systems
The -a option displays all file systems, including
pseudo, duplicate, and inaccessible ones, providing a comprehensive
view.
# List [a]ll filesystems, + unreadable, duplicates, pseudo, and inaccessible.
df -a
Grand Total Disk Usage
To get a summary of the total disk usage across all mounted file
systems, use the --total option.
# Fetch a grand total of disk usage.
df --total