Red Hat ENTERPRISE LINUX 4 System Administration Manual page 308

Chapter 31. X Window System Configuration
Figure 31.3. Dual Head Display Settings
To enable use of Dual head, check the Use dual head checkbox.
To configure the second monitor type, click the corresponding Configure button. You can also
configure the other Dual head settings by using the corresponding drop-down list.
For the Desktop layout option, selecting Spanning Desktops allows both monitors to use an
enlarged usable workspace. Selecting Individual Desktops shares the mouse and keyboard among
the displays, but restricts windows to a single display.
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