How to list the top 5 largest directories

# du -sk /opt/* | sort +0nr | head -5
25456556        /opt/data
12634192        /opt/read
5483564 /opt/download
196104  /opt/scripts
132964  /opt/freeware

tip.. if you want to include the hidden files and directories, try this.

# du -sk .[a-z]* * | sort +0nr | head -5