Red Hat LINUX VIRTUAL SERVER 4.6 - ADMINISTRATION Installationshandbuch PDF herunterladen (Seite 251)

Chapter 13. Miscellaneous tasks 231

13.9 The X Window System

For many years, UNIX-like operating systems have been using the X Window System. This

system was designed to provide a client/server, hardware-independent, and network-enabled

graphical environment. The current version is X Window System 11, which is widely used on

UNIX and Linux platforms.

Confusion often arises among new X Window System users regarding the concept of client

and server, because client and server are defined from an application point of view, where

other protocols, such as SSH, Telnet, and FTP, are defined from an user point of view. In the

X Window System, the server runs on a workstation or a desktop, while the client runs on the

UNIX or Linux server. Many Linux desktop users do not recognize this difference because

they often run both the server and client on their desktop.

It is a common practice to connect from a PC (SSH client) to a remote Linux system (SSH

server) and then run an X Window System application. It runs on a remote Linux system

(X Window System client) and displays on a local PC (X Window System server).

The X Window System communication protocol, by its nature, is not secure at all. For this

reason, it is often used together with the SSH protocol, which tunnels X Window System 11

traffic using encrypted (and thus secure) communications.

X Window System 11 itself provides the ability to display graphics on raster display only. If the

user wants to be able to move, resize, and otherwise manage windows, a

window manager is

required. There are many window managers available; some are lightweight, while some are

more robust. So using a window manager is a good idea, because it provides the functionality

that one expects from a GUI.

When you have Linux installed on your workstation, a window manager is probably not

enough. Here you want a full desktop environment with menus, icons, task bars, and so on,

such as Gnome and KDE. Installing GNOME or KDE on System z is discouraged, as they are

resource-intensive. Installing the X Window System on System z is also not recommended.

13.9.1 VNC server

As mentioned earlier, the X Window System server is run on the workstation. In a nutshell, a

VNC server provides a virtual workstation with all the peripherals (virtual). The VNC server

starts an embedded X Window System server. Then any X Window System-based

application can send its output to this X Window System server, regardless whether the

applications are local or remote to the X Window System server.

To interact with the X Window System server, one uses a VNC client on a workstation, as

described in 3.2, “Setting up a VNC client” on page 24. The VNC server customization is

described in 8.2.4, “Configuring the VNC server” on page 151. In our experience, this is all

you need if you want to run X Window System applications from time to time.

One big advantage of VNC is that it is session oriented. If communication to VNC server is

lost, a new connection is reestablished to the session as it was. Also, applications in a

disconnected VNC session still continue to run.

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Red Hat LINUX VIRTUAL SERVER 4.6 - ADMINISTRATION Installationshandbuch Seite 251