The GNOME Desktop Environment

The GNOME desktop environment, like KDE, is a complete desktop suite, from the desktop background up to a set of applications. As with KDE, GNOME can run any X application, and both KDE and GNOME rely on standards set by the Freedesktop.org group. In fact, the distinction between the two desktops is, in many ways, of interest more to developers choosing toolkits than to users, who in most cases mix and match applications without having to worry about the underpinnings.

The primary goals of the GNOME project are simplicity and ease of use. Applications must comply with extensive human interface guidelines to become part of the official GNOME desktop. Because GNOME makes an excellent platform for development in C, C++, Python, Java, and C#, unofficial and third-party applications are numerous. In some cases (notably the XML system), GNOME libraries appear in command-line and server-based applications.

Of course, for our purposes, the interesting parts are the core desktop and its associated applications. In the following sections, we go over the GNOME look and feel, talk a little bit about the customization options it offers to you, and then give a quick tour of major applications, such as Evolution and Nautilus.

Most Linux distributions include GNOME, but if you haven’t installed it yourself, or if you want a newer version, you can visit http://gnome.org or your distribution’s web page for downloads.

Core Desktop Interface

The GNOME desktop is designed to be familiar to anyone who has used a computer before. Although you can change the settings in almost any way, a typical installation will have a desktop with icons on it and a panel along the top and bottom. The panels are among the most important GNOME tools because they are so versatile and they allow a wide range of interactions with your system. Panels can exist along one edge of your screen, like the Windows control panel; along a portion of it, like the Macintosh Dock, and more. They can contain buttons to launch applications and small applications called applets such as clocks, system monitors, and even tiny games.

Basic GNOME tasks

Here is a quick explanation of how to perform the most common tasks . Once you get the hang of these, you can probably guess how to do anything else.

Open or activate an item in the panel: Click once with the left button.
Start a program: Buttons known as launchers cause a program to open when left-clicked; GNOME desktops typically have such buttons both in panels and on the desktop. Furthermore, when you click on a file, an appropriate program opens that file, as described shortly.
Move items around on the desktop: Click and drag with the left mouse button.
Move items in the panel: Clicking and dragging with the left mouse button works for launchers, but for some applets, the left mouse button is used to control the applet. In that case, middle-click and drag. This is also the case for moving windows by their borders—left-click will expand the window, but middle-click lets you move it.
Organize items on the desktop: Right-click the desktop background and select Clean Up by Name. Items will be arranged in alphabetical order, with two exceptions: the first item, in the upper left, is always your home directory, and the last item in the list is always the Trash folder.
Open or activate an item on the desktop: Double-click it. If you double-click a folder icon, it opens the folder in the Nautilus file management tool. If you double-click a spreadsheet document, the Gnumeric spreadsheet starts up and opens the document. If you have a window open and Shift-click or middle-click a folder in it, the current folder will close as a new one opens in its place.
Get a list of options or set preferences for any object: Click with the right mouse button to get a menu of available options for any object. For example, you can change the desktop background by right-clicking the background and choosing Change Desktop Background. More general preferences are available in the GNOME Control Center, which you can access by choosing System → Personal Settings or Applications → Desktop Preferences, or by typing gnome-control-center at the command line. The exact menu arrangements may vary slightly depending on your distribution and version.
Paste text into any text area: As with other operating systems, Ctrl-C copies, Ctrl-X cuts, and Ctrl-V pastes in every application except Emacs and XChat. You can also use the more traditional Unix mode pasting by selecting any text and then middle-clicking.

The panel

The preset configuration for many systems has a thin panel along the top and bottom of the screen. The top panel has a set of menus along the upper left, and a few buttons and a clock at the right. The bottom panel contains the window list applet, which should feel familiar to Microsoft Windows users; it displays a list of all open windows so you can switch applications easily.

To create a new panel, click any blank space in an existing panel, and choose Panel → Create New Panel, then select the type of panel you would like. To change a panel’s properties, such as its size and color, right-click it and choose Properties (the menu panel at the top of the screen has no available properties; it is preconfigured for one position and size). Experiment with different kinds of panels and with different sizes to see which ones you like best. If you use a smaller screen, such as a laptop screen, you will want to choose a smaller panel size than if you have plenty of screen real estate to use.

To add application launcher buttons to your panels, you can drag them from menus, or right-click the panel and choose Panel → Add to Panel Launcher. Then, enter the name of the application you want to run, and choose an icon. You may also choose a description of the launcher that will display as a tool tip when you hover the mouse over the icon in your panel. If you want to launch the application from a terminal, check the “Run in Terminal” box.

For more information on the panel, right-click any empty spot in the panel and select Panel → Panel Manual.

Panel applets are small applications that run inside the panel. You can add them to the panel from the Add to Panel menu or just run them by clicking Applications → Applets. Panel applets come in a bewildering variety of flavors, from games to utilities. Some of the most common are the following:

Notification Area: The notification area is similar to the Windows system tray and holds a variety of system status displays. Applications such as the Gaim instant messenger tool (described in “Instant Messaging” in Chapter 5) and the Rhythmbox music player use it as a control area that allows users to access them without keeping any windows open. System alerts and print queues will also display in this area. Both KDE and GNOME make use of the same notification area system, so applets that use the notification area will work in both desktops.
Netapplet: Netapplet runs in the notification area and allows you to browse and choose available wired and wireless network connections. This is particularly useful for laptop users who need to use Wi-Fi (802.11x) connections. To run Netapplet, you must also be running netdaemon.
System Monitor: A graph that displays the load on your system resources for the past few seconds. To get a more detailed system report, including a list of all running processes and applications, right-click on the applet and select Open System Monitor.
Workspace Switcher: In most installations, this applet will already be running when you log in, and is typically set to four workspaces. Each workspace is the equivalent of a new screenful of desktop space, and you can have as many as you like. The workspace switcher displays all the virtual workspaces you have created, and displays each window on the desktop as a tiny box. You can use the left mouse button to drag a window from one workspace to another. Right-click and select the Properties menu item to change the number or arrangement of workspaces.
Window List: Like the workspace applet, the Window List is included in most default configurations. It displays the windows that you have open so that you can switch easily among them, even when they are minimized. If you have multiple windows for a single application, they will be grouped under a single entry. To turn this feature off, or to set other options for the applet, right-click the Window List and select Properties.
Battery Charge Monitor: The Battery Charge Monitor displays the remaining battery life for laptop systems. You can also use the Battery Charge Monitor to put your system into “sleep” or “suspend” mode by right-clicking on the applet and selecting Suspend Computer. Resuming operation from suspend mode is faster than rebooting, but the mechanism for operation will vary depending on your hardware and distribution. Older systems with the Advanced Power Management system use the command apm -s. Newer systems with ACPI support need to be sure that they have ACPI events configured properly in /etc/acpi/events/default, although your distribution will probably have a convenient GUI for this task. For both ACPI and APM, SUSE Linux uses powersaved, and the sleep command is powersave --suspend.

Nautilus: your desktop and file manager

Nautilus is the name of the GNOME desktop and file manager. It controls the display of your background image and the files on your desktop, allows you to interact with files without using a terminal, and keeps track of your trash for you. In other words, it’s the GNOME equivalent of Windows Explorer, the Macintosh Finder, and KDE’s Konqueror. Like those other applications, Nautilus lets you drag items from one place to another. You can also copy files using Ctrl-C, cut with Ctrl-X, and paste with Ctrl-V.

Tip

In most cases, Nautilus will be running when you log in. If you don’t want to run Nautilus at all, you can remove it from your session with the Session Properties tool in the Control Center. If you change your mind and want to start it, the command is nautilus.

The quickest way to get started with Nautilus is to double-click the home icon in the upper-left corner of your desktop, labeled as your home. This will open your home directory. Nautilus varies from other file management systems in that a window not only displays a folder, but is the folder: if you open a folder, then double-click it to open it again, it will merely raise the first window. For that reason, the location bar you may expect at the top of a window is not present. Instead, press Ctrl-L to enter a file location.

Tip

Experts and those familiar with other file management systems will appreciate that Nautilus, although simple at first look, has a variety of conveniences and shortcuts that make advanced use much quicker. The first is Ctrl-L, which works not only in Nautilus but in all GNOME-related file selection dialogs to allow you to type a filename instead of clicking to choose a file. In web browsers, you can also use Ctrl-L to enter a web page instead of selecting the location bar with the mouse.

Opening windows: To avoid opening several windows at once, Shift-click or middle-click to close the current window when opening a new one.

Shortcuts for places: The combination Alt-Up opens the parent of the current folder, and Alt-Home opens your home directory.

If you prefer a more complex file display, right-click on any directory and choose Browse Folder . Browse mode includes the location bar absent from the normal Nautilus display mode, and also includes the left-side pane. At the top of the left pane is a selector for different information displays:

Information: Displays basic information about the current folder.
Emblems: Displays a list of available emblems, small badges you can add to any file’s icon. Drag them from the side pane onto any file to mark it. For example, if you have several similar images in a folder, you might want to drag the “Cool” or “Favorite” emblem to remind you which one you like best. You can also set emblems by selecting Edit → Background and Emblems.
History: Shows a list of previous locations you have displayed in Nautilus. Double-click any folder to return to it.
Notes: Allows a note to be kept on a particular folder. Each folder has a different page of notes.
Tree: Perhaps the most useful of the side-pane tools, this allows you to navigate a complex folder hierarchy with convenient spin-down triangles. Each folder in the tree is displayed with a triangle next to it; click the folder to open it, or click the triangle to display any subfolders without actually visiting the folder itself.

Some neat Nautilus features include the following:

Instead of a generic image icon for graphics files, Nautilus uses scaled-down thumbnails of the image itself. This makes it easy to organize directories full of images, such as those pulled from a digital camera.
If you hover your mouse over a music file, the file will begin to play.
For text files, the plain document icon is decorated by the actual text contents of the file. That way, you can remember how the file starts without having to open it, even if you didn’t give it the most descriptive name.
You can stretch icons by right-clicking them and choosing Stretch Icon. If you stretch a text icon enough, you can see the entire contents of the file, and use it as a desktop notepad.
Select Edit → Backgrounds and Emblems to choose different emblems to decorate icons. You can also drag colors and patterns from this area to set your desktop and panel background. To set an image as the desktop background, right-click on the desktop and choose Change Desktop Background.

All in all, Nautilus is a versatile tool that you can learn to use just by poking around a little. For additional help, just choose Help and then Nautilus User Manual from any Nautilus window.

Expert Settings: GConf

GConf is a centralized, XML-based configuration system for desktop applications. It allows applications to share keyboard shortcuts, themes, and other preferences, and uses a daemon to notify applications when preferences change, so you don’t have to restart the application to see a change take effect.

GConf can also be used to lock down a desktop system with a finer degree of granularity than traditional Unix file locking. An administrator might wish to lock GConf settings to permit some, but not all, behavior for a given application, and allow some, but not all, changes in preferences. Administrators of kiosks, public computer labs, and other security- and support-conscious deployments find system lockdown to be indispensable. Therefore, most applications provide a lockdown section in their GConf files. If you have users you want to keep out of trouble, explore these options in greater detail. One good resource is the GNOME System Administrator’s Guide, available at http://www.gnome.org.

In this book, we assume that you’re not interested in locking preferences down, but in opening things up and tweaking them to your taste. That’s where gconf-editor comes in handy. You can, of course, edit the XML files in ~/.gconf yourself, but the gconf-editor application makes things a little more convenient.

To get started, run the command gconf-editor. On the left side of the window is the GConf hierarchy, arranged like a file tree starting at /. The tree corresponds to actual settings files stored in the ~/.gconf directory, so changing something in the /applications tree alters files stored in ~/.gconf/applications. On the right side of the window is the list of available settings, called keys, and a place for documentation about the selected key.

We’re mostly interested in items under the /apps tree. The /desktop and /GNOME trees hold information not tied to a specific application, such as session data and desktop-wide lockdown settings. Systemwide configuration is stored in /system, and information about the way GConf stores settings is kept in /schemas. Avoid changing anything in the /schemas tree.

For now, let’s try adjusting an application setting, to give you a feel for what can be done. Normally, the files on your desktop come from the ~/Desktop folder. However, you can force Nautilus to display your home directory on the desktop instead. Select /apps/nautilus/preferences/desktop_is_home_dir and check the box. Now, Nautilus will display the contents of your home directory on your desktop.

Other applications have similar “hidden” preferences you can change. Try the following:

Metacity window manager: Check the box in /apps/metacity/reduced_resources to make Metacity use as few system resources as possible. This will make it look less attractive, but may improve system performance.
Epiphany web browser: Normally, a middle click in the Epiphany web browser turns on the vertical scroll feature familiar to users of Internet Explorer. However, users of traditional UNIX browsers may prefer to check the box for /apps/epiphany/general/middle_click_open_url and turn on the “paste URL” feature. Select a URL in any application, then middle-click in a non-text-entry area of a web page, and Epiphany will load the text you have selected.

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3.3. KDE Applications

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3.5. GNOME Applications