df - Linux

Overview

The df command in Linux stands for “disk free” and is used to report the amount of disk space used and available on file systems. This command helps users manage disk space by providing summaries of available and used disk capacities. It’s particularly useful in server environments and when monitoring system health and capacity.

Syntax

df [OPTIONS]... [FILE]...
  • [OPTIONS]: These are flags or arguments that modify the behavior of the command.
  • [FILE]: Optionally specify one or more files or directories to report on their file systems.

Options/Flags

  • -a, --all: Include dummy file systems in the output.
  • -h, --human-readable: Print sizes in a human-readable format (e.g., 1K, 234M, 2G).
  • -H: Similar to -h, but uses powers of 1000 not 1024.
  • -i, --inodes: List inode information instead of block usage.
  • --total: Produce a grand total.
  • -k: Display sizes in kilobytes (default).
  • -l, --local: Limit the listing to local file systems.
  • -T, --print-type: Show file system type.
  • --sync: Invoke sync before getting file system usage; ensures up-to-date information.
  • -t, --type=TYPE: Limit listing to file systems of type TYPE.
  • -x, --exclude-type=TYPE: Exclude file systems of type TYPE.
  • --no-sync: Do not invoke sync before getting file system usage (default behavior).

Examples

  1. Basic Usage: Show disk space usage of all mounted file systems: 
    df
  2. Human-Readable Format: Display the disk space in a more readable format: 
    df -h
  3. Specific File Systems: Show only the disk usage of type ‘ext4’: 
    df -t ext4
  4. Exclude File System Types: Avoid listing ‘tmpfs’ and ‘devtmpfs’ types in the output: 
    df -x tmpfs -x devtmpfs
  5. Display Inode Information: Report on inodes instead of block usage: 
    df -i

Common Issues

  • Exceeding File System Inodes: Users might ignore the inode limits as df primarily focuses on block usage. To monitor inodes, use df -i.
  • Permission Denied: Running df may result in “Permission Denied” for certain directories. Running it with sudo may be required.
  • Output Overwhelming: Particularly on systems with many mounts, the output might be excessive. Filtering with -t or -x can make the output manageable.

Integration

Combine df with other tools like grep for more effective space management:

df -h | grep '/dev'

This command chain helps focus on specific devices. It can be used in scripts or cron jobs to monitor disk usage regularly.

  • du – estimates file space usage.
  • fdisk – manipulates disk partition table.
  • mount – mounts file systems.

For further details on the usage and options, consult the man page (man df) or the GNU Coreutils online documentation: GNU Coreutils – df.