How to clear recently used files without using a terminal?
Solution 1:
It depends on whether you're using Unity or the Classic desktop.
In Unity, the recent documents that you see in the Files lens are logged using Zeitgeist. If you don't want to use the terminal to remove these, or only want to remove a few of them, the best thing to do is install "Activity Journal" using the Software Center. Fire up the Activity Journal, and you'll see all your recently used apps and documents, grouped by day. If you right click a document and click "Delete item from Journal", Zeitgeist will forget that you used that document at that specific time. If you click "Delete all items with this URL", Zeitgeist will forget you ever used that document. If you want to delete everything, this terminal command (which others have already posted) will do the job:
rm ~/.local/share/zeitgeist/activity.sqlite
zeitgeist-daemon --replace
There's a Zeitgeist Global Privacy app in development which will make this easier, but unfortunately it's not released yet.
The Classic desktop (and the lists of recently used files in most applications' File menus) stores a record of your recently used documents in ~/.local/share/recently-used.xbel. You can just delete this file using the file manager or copy and paste the following code into a terminal:
rm ~/.local/share/recently-used.xbel
Hope that helps!
Solution 2:
The only way I know how to do this is to install Ubuntu Tweak, which can be found by going to http://ubuntu-tweak.com/ and installing the software.
Open Ubuntu Tweak up and go to Gnome Settings then uncheck Enable System Wide "Recent Documents" List
Solution 3:
You can use bleachbit
from its homepage on SourceForge or install it through the Software Center.
It can delete all unnecessary files, and system cache.
Open BleachBit and then check your preferences:
for deleting recent documents, only select System→recent documents
Solution 4:
Upgrade to 12.04. It comes with a cleaner and settings wizard by default.
Under System Settings click Privacy, there is an option to clear the recent history.