Set keyboard shortcuts
To change the key or keys to be pressed for a keyboard shortcut:
Click the icon at the very right of the menu bar and select System Settings .
Open Keyboard and select the Shortcuts tab.
Select a category on the left side of the window, and the desired action on the right.
Click the current shortcut definition on the far right.
Hold down the desired key combination or press Backspace to clear.
To create your own keyboard shortcut:
Select Custom Shortcuts on the left side of the window.
Click the + button. The Custom Shortcut window will appear.
Write a Name to identify the shortcut, and a Command to run an application, then click Apply. For example, if you wanted the shortcut to open Rhythmbox, you could name it Music and use the rhythmbox command.
Double click where it says Disabled on the far right, and then hold down the desired shortcut key combination.
The command name that you type should be a valid system command. You can check that the command works by opening a Terminal and typing it in there. The command that opens an application may not have exactly the same name as the application itself.
If you want to change the command that is associated with a custom keyboard shortcut, double-click the name of the shortcut. The Custom Shortcut window will appear, and you can edit the command.