Most Linux systems include a periodic process to update the database. If your system returned an error with the above command such as the following, then you will need to run updatedb to generate the search database:

$ locate bin/ls
locate: /var/spool/locate/locatedb: No such file or directory
$ su
Password:
# updatedb

The updatedb command may take a long time to run. If you have a noisy hard disk, you will hear a lot of racket as the entire filesystem is indexed. :)