I've seen a lot of forum posts with questions about installing desktop managers such as Gnome and KDE after you perform the initial installation of Linux. Many of the issues seem to be related to installing the desktop environment without installing the X server. The thing to remember is that X provides the foundation for graphics in Linux/Unix. If you don't have X, you don't have graphics, so you have to install X before you can use the desktop environment. If you don't, you'll get errors such as "no server "X" in PATH" or "xinit: Server error"
Here's how to do it (two steps) on Red Hat-based systems (Red Hat, Fedora, CentOS):
- $ su -
- # yum groupinstall "X Window System"
- # yum groupinstall "GNOME Desktop Environment" or
- # yum groupinstall "KDE (K Desktop Environment)"
Presumably, it's similar on Debian systems, but you would use apt-get instead of yum.
If you want to go crazy with graphics, install beryl as well. Falco Timme as an excellent tutorial (all of his tutorials are excellent) at HowToForge.com.