Modern Linux system have all sorts of fake filesystems cluttering the output of df and mount: tmpfs, bind mounts, fuse for ~/.gvfs, etc. I have only one real partition on my laptop, yet mount returns 22 lines of output.
Question: are there any df-like utilities that filter out all the crap and show only interesting bits? The standard df as well as pydf both display 8 lines instead of 1. Discus is worse: it shows 20. GUI utilities like Baobab also suffer from this confusion, especially bind mounts.
Ironically, Ubuntu's update-motd gets confused by Ubuntu's private user directories and displays disk stats for ~/Private as if it were a real partition.