If you want to search for specific files on ubuntu linux then some of your options are as follows:
1. Find command, using this command you can find specific file on ubuntu.
2. Use Places | Computer (or Places | Home or any other location) and then use the ’search’ button (its a looking-glass icon).
3. Use following commands on terminal for creating index and then search file from it.
* updatedb
* locate
The first command create a index, the second use the index to search.
4. Use Beagle or Tracker. (If you’re using gnome then “do” will help)