The X Administration Philosophy

On top of the Xt additional GUI libraries are layered, and they actually, together with a window manager, make a full GUI support. • The three most common GUIs were provided by the Athena widgets, the OSFMotif, and the OPEN LOOK specifications. Each of those specifications also included the corresponding window manager; fortunately, a set of conventions provides interoperability of clients and window managers from different X−based GUIs. Supposing that the X design is more clear now, let us summarize briefly how everything works. X clients and X servers communicate mutually using the X protocol they understand very well. This communication could be local both the X client and X server live on the same machine or remote through the network. X protocol relates to the GUI objects that are well known to both sides in the communication. Instead of transferring large descriptions of the wanted graphic presentations, short messages that refer to appropriate GUI elements are used. We still have the full flexibility with preserved fast communication between a client and a server. In the worst case, when a wanted graphic presentation is not covered by the GUI objects, a full graphic image could be transferred; however, it happens only occasionally. Of course, the price that must be paid is both sides in such a communication, an X client and an X server, should support X protocol. Benefits in using X windowing are numerous. X enables a flexible distribution of resources within the network. The execution of an application and the interaction with the very same application are divided, and could be arbitrary located, optimizing the efficient use of available resources. A number of users could access simultaneously a number of applications, by making an optimal balance between processing and displaying resources. In the distributed computer environment, X makes a step closer to the dream of having a whole network that appears as a single equivalent powerful processing computer system.

22.1.2 The X Administration Philosophy

The basic philosophy that X is built on is that X provides a mechanism, not a policy. This is a good approach if you have in mind future development and improvements. However, from an administrative standpoint it makes maintenance more difficult. The lack of strict rules and standards left vendors free to create their own rules, and X administrators without much guidance. There are many different flavors of X: the standard X11 distribution maintained by the X Consortium; then various vendor−configured versions that are derived from MIT X11 but configured for a vendors operating system and proprietary look and feel. There are Open Windows, which runs on Sun platform; DECWindows, which runs on DEC platform; AIXWindows, which runs on IBM AIX platform; VUE Visual User Environment, which runs on HP−UX platform; and more. Common Desktop EnvironmentCDE seems to be a successful attempt to bring a common X platform as a standard; as far it was accepted by most of the vendors and combined with vendor−specific X packages. This means that X could behave differently on different UNIX platforms. An administrator can easily realize that the system reacts differently than expected. The fact that the X Consortium provides only the mechanism and relies on vendors to decide how to use it, made some holes and gaps in the implementation. An administrator must be aware of what is hidden under the hood, before using that. This is one of the most difficult issues in X administration. Despite that X is supported by relatively ample documentation the word here is about online documentation — manual pages, to 517 Nevertheless, to come out with the issue of a philosophy of X administration, it would be that X is made to fit the needs of its users. The administrator has the responsibility to determine the users need and configure X accordingly. X is installed in all sorts of environments, from academia, via industry, to home offices with a single standalone machine. For that reason, almost everything in X is configurable at multiple levels. The X Display Manager can be configured in several different places, to meet practically any need. Even the source code to X is available for those who want to create their own workarounds. The fundamental idea is that if you do not like the way something is working, change it. We will continue our discussion about X having in mind the standard X distribution, especially its CDE release. However, to copy with the CDE, an appropriate knowledge of older X releases is required. Finally, through a number of examples we will also touch some vendor−specific flavors mostly HP VUE. The full understanding of the standard X distribution is a giant step in maintaining other vendor−specific X flavors.

22.1.3 Window Managers