du , df and ls commands show different
results for the same Disk block , the reason is
* 'ls' gives data on individual files based on
the difference between the end-of-file and the beginning-of-file, whether or
not blocks were actually allocated to the file
* 'du' shows the blocks actually allocated to
an individual file
* 'df' shows the blocks allocated in the
entire file system, including inodes and other meta data
