There are situations when we need to make file deletion unrecovarable for security concerns. There are simple commands that can do this. Open a terminal and type the following command.
dd ip=/dev/urandom op=~/consumeSpace.txt
This will fill up all space left with random characters and once the space gets over it stops by throwing an exception. Now we can delete the file we have created to free up the space. To delete the file created type the following command into a terminal.
rm ~/consumeSpace.txt
We have now deleted the files permanently from the disk.