To change the key or keyboard shortcut: keyboard screen shot Select a category screen shot
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 in the left pane, and the row for the desired action on the right. The current shortcut definition will change to New accelerator…
Hold down the desired key combination, or press Backspace to clear.
To create your own keyboard shortcut:
Select Custom Shortcuts in the left pane, and click the + button (or click the + button in any category). The Custom Shortcut window will appear.
Type 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
Click Disabled in the row that was just added. When it changes to New accelerator…, 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.