The df utility displays statistics about the amount of free disk space on the specified file system or on the file system of which file is a part. Values are displayed in 512-byte per block counts. If neither a file or a file system operand is specified, statistics for all mounted file systems are displayed.
Use df -h to see the output “Human-readable” output. Uses unit suffixes: Byte, Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte.
# df -h Example:
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 19G 14G 4.0G 78% /
tmpfs 501M 0 501M 0% /lib/init/rw
udev 10M 48K 10M 1% /dev
tmpfs 501M 0 501M 0% /dev/shm