The ncdu command provides a useful and convenient way to view disk usage. The name stands for “NCurses disk usage”. This means that it’s based on ncurses which, like curses, is a terminal control library used on Unix/Linux systems. The curses part of each name is a pun on “cursor” or “cursor optimization” and is unrelated to the use of foul language.
You can think of ncdu as a disk usage analyzer with an ncurses interface. It can be especially useful when looking for disk-space hogs on a remote server for which you don’t have access to a graphical interface.
To use ncdu, you can just type “ncdu”, but what you will see depends on where you have positioned yourself in the file system as it reports the space used by files and directories in that location.
Source:: Network World – Linux