Common Linux Features

No matter what version of Linux you use, the piece of code common to all is the Linux kernel. Although the kernel can be modified to include support for the features you want, every Linux kernel can offer the following features:

• Multiuser - Not only can you have many user accounts available on a Linux system, you can also have multiple users logged in and working on the system at the same time. Users can have their own environments arranged the way they want: their own home directory for storing files and their own desktop interface (with icons, menus , and applications arranged to suit them). User accounts can be password-protected, so that users can control who has access to their applications and data.

• Multitasking - In Linux, it is possible to have many programs running at the same time, which means that not only can you have many programs going at once, but that the Linux operating system can itself have programs running in the background. Many of these system processes make it possible for Linux to work as a server, with these background processes listening to the network for requests to log in to your system, view a Web page, print a document, or copy a file. These background processes are referred to as daemons.

• Hardware support - You can configure support for almost every type of hardware that can be connected to a computer. There is support for floppy disk drives, CD-ROMs, removable disks (such as DVDs and pen drives ), sound cards, tape devices, video cards, and most anything else you can think of. As device interfaces, such as USB and FireWire, have been added to computers, support for those devices has been added to Linux as well.

  For Linux to support a hardware device, Linux needs a driver, a piece of software that interfaces between the Linux kernel and the device. Drivers are available in the Linux kernel to support hundreds of computer hardware components that can be added or removed as needed.

  Note 

  Most hardware manufacturers don't provide Linux drivers with their peripheral devices and adapter cards. Although most popular hardware will be supported eventually in Linux, it can sometimes take a while for a member of the Linux community to write a driver. Also, some outdated hardware my not be updated to work with the latest Linux kernels .

• Networking connectivity - To connect your Linux system to a network, Linux offers support for a variety of local area network (LAN) cards, modems, and serial devices. In addition to LAN protocols, such as Ethernet (both wired and wireless), all the most popular upper-level networking protocols can be built-in. The most popular of these protocols is TCP/IP (used to connect to the Internet). Other protocols, such as IPX (for Novell networks) and X.25 (a packet-switching network type that is popular in Europe), are also available.

• Network servers - Providing networking services to the client computers on the LAN or to the entire Internet is what Linux does best. A variety of software packages are available that enable you to use Linux as a print server, file server, FTP server, mail server, Web server, news server, or workgroup (DHCP or NIS) server.

Note 

Because of the popularity of the RPM Package Management (RPM) format for packaging software, many software packages are available on the Internet in RPM format. If the RPM version matches your Linux distribution and processor type (most have i386 and or i686 versions available), you can install the package without building and compiling the package. In fact, there are major software repositories that include software packaged specifically for the latest Fedora distribution. See Chapter 5 for information on working with RPM packages and software repositories. In particular, the yum utility is used to install RPM packages in Fedora because of its ability to handle software dependencies and access remote data bases.

To make a Linux distribution useful, components need to be added on top of the Linux kernel. For humans to access a Linux system, they can enter commands to a shell or use graphical interfaces to open menus, windows , and icons. Then you need actual applications to run. Those features include:

• Graphical user interface (X Window System) - The powerful framework for working with graphical applications in Linux is referred to as the X Window System (or simply X). X handles the functions of opening X-based graphical user interface (GUI) applications and displaying them on an X server process (the process that manages your screen, mouse, and keyboard).

  On top of X, you use an X-based desktop environment to provide a desktop metaphor and window manager to provide the look-and-feel of your GUI (icons, window frames , menus, and colors, or a combination of those items called themes ). There are several desktop environments and several desktop managers to choose from. (Fedora and RHEL focus on the GNOME and KDE desktop environments, but make several other desktop environments and window managers available in Fedora Extras.)

• Application support - Because of compatibility with POSIX and several different application programming interfaces (APIs), a wide range of freeware and shareware software is available for Linux systems. Compatibility with the GNU C libraries is a major reason for the wide- ranging application support. Most GNU software from the Free Software Foundation will run in Linux (although some may take a bit of tweaking).