10.4.3. Problems with the X Window System (GUI)
If you are having trouble getting X (the X Window System) to start, you may not have installed it during your installation.
If you want X, you can either install the packages from the Red Hat Enterprise Linux installation media or perform an upgrade.
If you elect to upgrade, select the X Window System packages, and choose GNOME, KDE, or both, during the upgrade package selection process.
Refer to Section 35.3, “Switching to a Graphical Login” for more detail on installing a desktop environment.