X11 is the graphical system most widely used on Unix-like systems (also available, in addition to the native system, for Windows and Mac OS). Strictly speaking, the “X11” term only refers to a protocol specification, but it's also used to refer to the implementation in practice.
X11 had a rough start, but the 1990's saw XFree86 emerge as the reference implementation because it was free software, portable, and maintained by a collaborative community. However, the rate of evolution slowed down near the end when the software only gained new drivers. That situation, along with a very controversial license change, led to the X.org fork in 2004. This is now the reference implementation, and Debian Squeeze uses X.org version 7.5.
Current versions of X.org are able to autodetect the available hardware: this applies to the video card and the monitor, as well as keyboards and mice; in fact, it's so convenient that the package no longer even creates a /etc/X11/xorg.conf configuration file. This is all made possible by features provided by the Linux 2.6 kernel (in particular for keyboards and mice), by having each driver list the video cards it supports, and by using the DDC protocol to fetch monitor characteristics.
The keyboard configuration is currently set up in /etc/default/keyboard. This file is used both to configure the text console and the graphical interface, and it is handled by the keyboard-configuration package. Details on configuring the keyboard layout are available in Section 8.1.2, “Configuring the Keyboard”.
The xserver-xorg package provides a generic X server, as used by the 7.x versions of X.org. This server is modular and uses a set of independent drivers to handle the many different kinds of video cards.
Note that if the detected video card is not handled by any of the available drivers, X.org tries using the VESA driver. This is a generic driver that should work everywhere, but with limited capabilities (fewer available resolutions, no hardware acceleration for games, and so on). The X server writes its messages to the /var/log/Xorg.0.log log file, which is where one would look to know what driver is currently in use. For example, the following snippet matches what the intel driver outputs when it is loaded:
(==) Matched intel as autoconfigured driver 0
(==) Matched vesa as autoconfigured driver 1
(==) Matched fbdev as autoconfigured driver 2
(==) Assigned the driver to the xf86ConfigLayout
(II) LoadModule: "intel"
(II) Loading /usr/lib/xorg/modules/drivers/intel_drv.so
EXTRA Proprietary drivers
Some video card makers (most notably nVidia) refuse to publish the hardware specifications that would be required to implement good free drivers. They do, however, provide proprietary drivers that allow using their hardware. This policy is nefarious, because even when the provided driver exists, it is usually not as polished as it should be; more importantly, it does not necessarily follow the X.org updates, which may prevent the latest available driver from loading correctly (or at all). We cannot condone this behaviour, and we recommend you avoid these makers and favour more cooperative manufacturers.
If you still end up with such a card, you will find the required packages in the non-free section: nvidia-glx for nVidia cards, and fglrx-driver for some ATI cards. Both cases require matching kernel modules. Building these modules can be automated by installing the nvidia-kernel-dkms (for nVidia), or fglrx-modules-dkms (for ATI) packages.
The “nouveau” project aims to develop a free software driver for nVidia cards. As of Squeeze, its feature set does not match the proprietary driver. In the developers' defense, we should mention that the required information can only be gathered by reverse engineering, which makes things difficult. The free driver for ATI video cards, called “radeon”, is much better in that regard.
13.2. Customizing the Graphical Interface
13.2.1. Choosing a Display Manager
The graphical interface only provides display space. Running the X server by itself only leads to an empty screen, which is why most installations use a display manager to display a user authentication screen and start the graphical desktop once the user has authenticated. The three most popular display managers in current use are gdm3 (GNOME Display Manager), kdm (KDE Display Manager) and xdm (X Display Manager). Since the Falcot Corp administrators have opted to use the GNOME desktop environment, they logically picked gdm3 as a display manager too. The /etc/gdm3/daemon.conf configuration file has many options, some of which can also be set by gdmsetup, a graphical interface for gdm3 configuration that can be run from the System → Administration → Display screen menu in the GNOME desktop.
ALTERNATIVE gdm vs. gdm3
A fresh installation of Squeeze sets up gdm3. On the other hand, a system upgraded to Squeeze from a previous version of Debian will usually have gdm (the 2.x version). Version 3 is a full rewrite, but it is still rather young: many of the options provided by previous versions have been removed, and the gdmsetup configuration interface is much more limited in scope. This explains why both versions are available in Squeeze. Note, however, the 2.x versions will be removed from the next stable Debian release. It makes sense to anticipate the migration and install gdm3 straight away if the missing features are not important to you.
13.2.2. Choosing a Window Manager
Since each graphical desktop provides its own window manager, choosing the former usually implies software selections from the latter. GNOME uses the metacity window manager, KDE uses kwm (KDE Window Manager), and XFce (which we present later) has XFwm. The Unix philosophy always allows using one's window manager of choice, but following the recommendations allows an administrator to best take advantage of the integration efforts led by each project.
BACK TO BASICS Window manager
True to the Unix tradition of doing one thing only but doing it well, the window manager displays the “decorations” around the windows belonging to the currently running applications, which includes frames and the title bar. It also allows reducing, restoring, maximizing, and hiding windows. Most window managers also provide a menu that pops up when the desktop is clicked in a specific way. This menu provides the means to close the window manager session, starting new applications, and in some cases, change to another window manager (if installed).
Older computers may, however, have a hard time running heavyweight graphical desktop environments. In these cases, a lighter configuration should be used. "Light" (or small footprint) window managers include WindowMaker (in the wmaker package), Afterstep, fvwm, icewm or blackbox. In these cases, the system should be configured so that the appropriate window manager gets precedence; the standard way is to change the x-window-manager alternative with the update-alternatives --config x-window-manager command.
DEBIAN SPECIFICITY Alternatives
The Debian policy lists a number of standardized commands able to perform a particular action. For example, the x-window-manager command invokes a window manager. But Debian does not assign this command to a fixed window manager. The administrator can choose which manager it should invoke.