Finding the disk used space

Here's a handy command sequence which you can run anywhere, anytime, so see which directories contain the most amount of data. It's a really useful way to focus your attention on the biggest users of disk space. It's best run as root, so you have access to everyone's files:

# du -k / | sort -rn | less

* 'du -k / ' means "Show me disk usage (in kilobytes) for all directories mounted on /"
* 'sort -rn' means "Sort in reverse numeric order (largest first)"
* 'less' is a handy favourite pager.

This will give you a list of directory sizes followed by the directory name. The top ones are where you should focus your attention.