df

df

The df command in Unix-like operating systems is used to display information about disk space usage on filesystems. It stands for "disk free". Here’s an overview of df and its common usage:

Overview of df

Purpose: df is used to report the amount of disk space used and available on filesystems mounted in the system.

Availability: df is a standard command-line utility available on Unix-like systems, including Linux distributions, macOS, and BSD variants.

Common df Commands and Usage

1. Display Disk Space Usage for All Filesystems:

   • To display information about all mounted filesystems:

     df

     By default, df displays information in 1 KB blocks.

2. Display Disk Space Usage in Human-Readable Format:

   • To display disk space usage in a more human-readable format (e.g., in kilobytes, megabytes, gigabytes):

     df -h

     The -h option (or --human-readable) converts sizes into a human-readable format.

3. Display Disk Space Usage for Specific Filesystem:

   • To display disk space usage for a specific filesystem (e.g., /dev/sda1):

     df -h /dev/sda1

     Replace /dev/sda1 with the device or mount point you want to inspect.

4. Display Filesystem Type:

   • To display the type of filesystem along with disk space usage:

     df -T

     The -T option (or --print-type) adds a column showing the filesystem type.

5. Display Inode Usage:

   • To display inode usage (number of used and available inodes) instead of disk space:

     df -i

     The -i option (or --inodes) switches df to report inode usage instead of disk space.

6. Display Total Disk Space Usage:

   • To display the total disk space usage across all filesystems:

     df -h --total

     The --total option provides a summary at the end of the output, showing the total used and available disk space.

Considerations

• Reserved Space: By default, df shows the amount of disk space available to ordinary users. Some filesystems reserve a percentage of disk space for root user (root-reserved). This reserved space is not shown as available to normal users.

• Symbolic Links: df does not follow symbolic links. It reports on the filesystem that contains the symlink's target.

• Performance Impact: Running df on large filesystems or with the -i option for inode information can be resource-intensive.

Alternatives

• pydf: A Python-based tool that provides an enhanced and colorful output of disk usage, similar to df.

• Disk Usage Analyzers: Graphical tools like Baobab (for GNOME) and Filelight (for KDE) offer visual representations of disk usage.

Conclusion

df is a fundamental command-line tool for monitoring disk space usage on Unix-like systems, providing essential information about available storage and filesystem types. It’s useful for managing disk resources, identifying available space, and planning storage allocation.

help

df [options] [filesystems]

Display filesystem disk space usage.

Options:

-a, --all    show all filesystems
-h, --human-readable   print sizes in human-readable format
-k, --kilobytes    use 1024-byte blocks
-m, --megabytes   use 1048576-byte blocks
-t, --type=TYPE   show only filesystems of the specified type
-T, --print-type   print the filesystem type
-H, --si    use powers of 1000 instead of 1024
-i, --inodes   print inode usage
-x, --exclude=FSTYPE   exclude filesystems of the specified type
-P, --portability   print in a format compatible with other systems
-S, --sync    force filesystems to be synced before displaying information
-v, --verbose   print more information
-?, --help     display this help message

Examples:

    df
    df -h
    df -T
    df -i
    df -x ext4