ansh0l's answer is the way to go to find large files. But, if you want to see how much space each directory in your files system is consuming, cd to the root directory, then do du -k --max-depth='. This will show you how much space is being consumed by each subdirectory within the root directory. When you spot the culprit, cd to that directory then run the same command again, and repeat, until you find the files that are consuming all of the space.
