Install safe-rm
From http://duntuk.com/
How to prevent accidentally doing “rm -rf /” | How to Install safe-rm
As a server administrator, I rely mostly on root or sudo access–allowing me absolute control of the server. However, “with great power, comes great responsibility!”
You can easily accidentally do this devastatingly bad command of wiping your entire system clean.
rm -rf / # or rm -rf /*
Which looks almost identical to the popular command
rm -rf ./ # or rm -rf ./*