Linux Command Line - Disk Usage and Disk Filesystem

July 4, 2017

du displays disk usage information and df displays disk filesystem information. These commands also work on Mac OS X.

Disk Usage

du <path> displays size of each subdirectory in the path and the total sum of the size of all directories in the path in bytes. du is equivalent to du ./.

du -h displays the data in human readable format. It round sizes up to their largest unit and the unit abbreviation: bytes B, kilobytes K, megabytes M, gigabytes G, etc.

du -sh provides the total size of the path in human readable format. It may be slow if there are many subdirectories.

Data sizes

Disk Filesystem

df displays device name, block size, disk space, used disk space, available disk space and mount points.

df -h displays the same as above but in human readable format.


A sequence of bytes or bits of a particular length, the block size. Putting data into blocks is blocking and extracting data from a block is deblocking. It helps reduce overhead and speed up data streams.


mount command instructs an operating system that a file system is ready for use. It associates a point in the file system (the mount point) to another file system. File systems, files, directories and devices (USB, CD-ROMs, DVDs, etc.) can be mounted.

umount dissociates a mount point from its filesystem.

device name

A device file is an interface for a device driver that appears in the file system as if it were an ordinary file. In Unix systems most devices appear as files in a virtual file system.


A Unix data structure that describe objects in a file system like files and directories. It stores disk block location, owner and permissions data and time of last change, access and modification.

POSIX standards requires the following: