Linux+: Linux X Window 01 – Introduction

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Jarret W. Buse

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Linux+: Linux X Window 01 – Introduction

Originally, most Operating Systems (OS) were command-line based. Over the years, nearly every OS has adopted a Graphical User Interface (GUI). Linux has been no exception to having a GUI. For the Linux+ Certification, you need to know about the X Window System (sometimes referred to as X11, X-Windows and X).

Like most other GUI systems, X11 provides the GUI environment of drawing windows and allowing them to be moved and resized.

X was originally developed at the Massachusetts Institute of Technology (MIT) in 1984 and has been called X11 since 1987. The X11 name is derived from the version number. The X Project has been taken over by the X.Org Foundation (http://www.x.org).

The reason for X11 is to provide the GUI to the user so using the OS is simpler than a command-line based OS. One main point is that X11 is architecture independent. X11 can be used with any OS that will support it. X11 can be used with a mouse, keyboard or touchscreen. X11 also provides the ability to receive the GUI or part of the GUI from an X11 Server. The X11 Protocol can be used to stream window data across a network to client systems.

The X11 Client-Server model works like this:

  1. The X-Server communicates with user applications
  2. input is accepted from a mouse, keyboard or touchscreen, whichever is set by the application being used
  3. Display output is shown on the monitor
  4. Access from remote system using a browser of terminal, the GUI, can be monitored as well over the network
Remote X11 is primarily used for Remote Desktop Administration, but other uses do exist for it:

  • Using a faster system remotely to execute the client application
  • Collaboratively working as a group on a single, centralized project
  • Displaying an output to numerous displays that is controlled by one set of I/O devices such as a lecture hall
X11 provides no specific shapes, sizes, colors, etc. for windows and its components. Specifics are controlled by the OS itself, by the Windows Manager, which in most cases can be configured by the user. On some OS systems the buttons on the window (minimize, maximize and close) can be placed in various spots within the window itself. Usually they are placed in the top right corner to be similar to Microsoft Windows, but these can be changed.

To cover more of the remote accessibility of X11, there are the X Terminals. The X Terminal is a “thin client”. A thin client is a system with no local hardware except the mouse, keyboard and monitor or a touchscreen monitor. Other devices may exist, especially to connect the local devices to a remote server. The remote server provides all processing for the running applications and the resulting screen image is sent to the remote monitor. In comparison, thin clients are inexpensive compared to a standard desktop system or “fat client”. By saving money on client systems, more money can be spent on the server to provide a better environment for the user.

To determine if you are running X11 on your Linux distro, run the following command in a terminal:

xdpyinfo | less

The output should display something similar to the following information on the first screen:

name of display: :0
version number: 11.0
vendor string: The X.Org Foundation
vendor release number: 11501000
X.Org version: 1.15.1


The “vendor string” shows it is the X.Org Foundation and the “version number” is 11.

Another part of the graphical environment is the Display Manager. The Display Manager configures the graphical environment such as: X Display Manager (xdm), GNOME Display Manager (gdm) and KDE Display Manager (kdm).

Another component of X11 are Widgets. Widgets handle the generation and use of scroll bars, menus, task bars, etc. The Widgets can be GTK, Qt and others.

To keep the user environment the same, the Desktop Environment is used. The Desktop will maintain the same widgets after every login unless other X11 components are changed. For example, to change the Display Manager would cause the desktop to most likely appear differently.

For applications on a system, the applications use Application Program Interfaces (APIs) which provide interfaces which will match all the applications on a system. For example, all applications on a system should have identical menu bars, scroll bars, title bars, etc.

To learn more about X11, open a terminal and type “man x”.
 

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