Mastering the Linux df Command: Practical Examples for Disk Space Management

Overview

The df command reports disk space usage for mounted filesystems on Linux. It can display information in various formats, making it a versatile tool for system administrators and developers who need to monitor storage.

Human‑Readable Output

By default df shows sizes in 1‑kilobyte blocks, which can be hard to read. Adding the -h option prints sizes in a human‑readable format (e.g., 100K, 200M, 3G).

$ df -h

Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu-root 909G 565G 299G  66% /
none                     4.0K   0  4.0K   0% /sys/fs/cgroup
udev                     3.9G 4.0K 3.9G   1% /dev
...

Displaying Inode Usage

Inodes store metadata for files. A filesystem can run out of inodes even if space remains, especially when many small files exist. Use the -i option to view inode statistics.

$ df -i

Filesystem               Inodes   IUsed   IFree IUse% Mounted on
/dev/mapper/ubuntu-root 60514304 1217535 59296769   3% /
...

Total Disk Usage Across All Filesystems

To see the combined usage of all mounted filesystems, add the --total flag.

$ df -h --total

Filesystem               Size  Used Avail Use% Mounted on
... (individual lines) ...
total                  918G 565G 307G  65% -

Showing Filesystem Types

The -T option adds a column with the filesystem type (e.g., ext4, tmpfs).

$ df -T

Filesystem               Type   1K-blocks    Used Available Use% Mounted on
/dev/mapper/ubuntu-root ext4   952893348 591583292 312882844 66% /
...

Including or Excluding Specific Filesystem Types

Use -t to include only certain types (repeatable) and -x to exclude types.

$ df -t ext2 -t ext4

Filesystem               1K-blocks    Used Available Use% Mounted on
/dev/mapper/ubuntu-root 952893348 591583380 312882756 66% /
/dev/sda1               233191    100025 120725   46% /boot

$ df -x tmpfs

Filesystem               1K-blocks    Used Available Use% Mounted on
... (output without tmpfs entries) ...

Querying a Specific Mount Point or Path

Providing a mount point or any file/directory path makes df report the filesystem that contains it.

$ df /

Filesystem               1K-blocks    Used Available Use% Mounted on
/dev/mapper/ubuntu-root 952893348 591583528 312882608 66% /

$ df /home/dev

Filesystem               1K-blocks    Used Available Use% Mounted on
/dev/mapper/ubuntu-root 952893348 591583528 312882608 66% /

Including Virtual Filesystems

Virtual filesystems (e.g., proc, sysfs, tmpfs) have no physical storage. Use -a to list them as well.

$ df -a

Filesystem               1K-blocks    Used Available Use% Mounted on
/dev/mapper/ubuntu-root 952893348 591578716 312887420 66% /
proc                     0          0          0      - /proc
sysfs                     0          0          0      - /sys
...