How to display free disk space of drives (hard disk)

On December 8, 2009, in df, disk space, by Dipin Krishna

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. […]