Investigating rising disk space usage on an Ubuntu web server

Since I set up daily logwatch emails on my Ubuntu web server, I’ve noticed the disk usage slowly creeping up each day – starting at 25% in January, and now at 47%, 10 months later. Left unchecked, this would likely fill my disk in a year or two’s time. So I figured I should try to diagnose what was eating up the free space, and decide whether it could be stopped/reduced. I started by looking at…