Ubuntu SOS

This is a very simple terminal feature that can be very useful and save you plenty of time. When you need to execute a recently used command you could just simply hit the UP arrow to allows you to individually see your recent commands as you press the button. The history command is just an extension of the UP arrow, except you get a whole list of past entries listed by the date they were entered. Simply enter history in the terminal

I'm not sure how many entries it keeps by default, but for myself i was able to see the first command I entered upon installation of Hardy.
Bash also allows for incremental search on the history list. Use ctrl+r for a backward/reverse search or ctrl+s to perform a forward search. As you type the first few letters of the command, the last command from the history list that matches with your string would be displayed.

Checkout http://www.ss64.com/bash/history.html for full information on expanding the history command.