If we have used Gnome Shell in Ubuntu Oneiric, one of the things we might realize is that the “Alt + F2″ shortcut keys to open the Run prompt is no longer working. In fact, the “Alt + F2″ shortcut keys was disabled for unknown reason. Anyway, as with all Linux distro, we can customize almost everything you want. Here’s how we can fix the issue and reactivate the “Alt + F2″ shortcut keys:

Click System Settings and click the “Keyboard” icon.

Click on the “Shortcuts” tab. On the left panel, select “System”.
On the right, select the first entry “Show the run command prompt” and click on “Disabled” to activate it.
Now we should see “New shortcut…”
Now press “Alt + F2″. It would show on the screen.
Now close the window and restart the computer.
“ALt + F2″ shortcut key should activate the RUN prompt after boot up.