Networking For Dummies

Linux, the free operating system based on Unix, is becoming more and more popular as an alternative to expensive server operating systems, such as Windows Server 2003 and NetWare. In fact, by some estimates, more computers are now running the Linux operating system than they're running the Macintosh operating system. You can use Linux as a Web server for the Internet or for an intranet, and you can use it as a firewall or a file-and-print server on your local area network.

Linux was created in 1991 by Linus Torvalds, who was at the time an undergraduate student at the University of Helsinki in Finland. Linus thought it'd be fun to create his own operating system based on Unix for his brand-new PC. In the nearly ten years since Linux was first conceived, Linux has become a full-featured operating system that is fast and reliable.

This chapter shows the basics of setting up a Linux server on your network and using it as a file server, as a Web server for the Internet or an intranet, as an e-mail server, and as a router and firewall to help connect your network to the Internet.

Comparing Linux with Windows

If your only computer experience is with Windows, you're in for a steep learning curve when you first get into Linux. There are many fundamental differences between the Linux operating system and Windows. Here are some of the more important differences:

• Linux is a multiuser operating system. Therefore, more than one user can log on and use a Linux computer at the same time:

  • Two or more users can log on to a Linux computer from the same keyboard and monitor by using virtual consoles, which let you switch from one user session to another with a special key combination.

  • Users can log on to the Linux computer from a terminal window running on another computer on the network.

  TECHNICAL STUFF

  Most versions of Windows are single-user systems. Only one user at a time can log on to a Windows computer and run commands. (Windows 2003 can be configured as a multiuser system with terminal services.)

• Linux doesn't have a built-in graphical user interface (GUI) as Windows does. Instead, the GUI in Linux is provided by an optional component called X Window System. You can run Linux without X Window, in which case you interact with Linux by typing commands. If you prefer to use a GUI, you must install and run X Window.

  TECHNICAL STUFF

  X Window is split into two parts: A server component (X server) manages multiple windows and provides graphics services for application programs. A user interface component (window manager) provides user interface features, such as menus, buttons, toolbars, and a taskbar.

  Several window managers are available, each with a different look and feel. With Windows, you're stuck with the user interface that Microsoft designed. With Linux, you can use the user interface of your choosing.

• Linux can't run Windows programs. Therefore, you can't run Microsoft Office on a Linux system; instead, you must find a similar program that's written specifically for Linux. Many Linux distributions come with an office suite called StarOffice, which provides word processing, spreadsheet, presentation, graphics, database, e-mail, calendar, and scheduling software. Thousands of other programs are available for Linux.

  TECHNICAL STUFF

  Windows emulator programs-the best-known is Wine-can run some Windows programs on Linux. But the emulators run only some Windows programs, and they run them slower than they would run on a Windows system.

• Linux doesn't do Plug and Play the way Windows does. Major Linux distributions come with configuration programs that can automatically detect and configure the most common hardware components, but Linux doesn't have built-in support for Plug-and-Play hardware devices. You're more likely to run into a hardware-configuration problem with Linux than with Windows.

• Linux uses a different system for accessing disk drives and files than Windows does. For an explanation of how the Linux file system works, see the "I can't see my C drive!" sidebar that's coming up in this chapter.

• Linux runs better on older hardware than the current incarnations of Windows do. Linux is an ideal operating system for an older Pentium computer with at least 32MB of RAM and 2GB of hard-drive space.

  TECHNICAL STUFF

  If you're fond of antiques, Linux can run well on even a 486 computer with as little as 4MB of RAM and a few hundred MB of disk space.

Well, no, but that's normal. Linux and Windows have completely different ways of referring to your computer's disk drives and partitions. The differences can take some getting used to for experienced Windows users.

Windows uses a separate letter for each drive and partition on your system. For example, if you have a single drive formatted into three partitions, Windows identifies the partitions as drives C, D, and E. Each of these drives has its own root directory, which can in turn contain additional directories used to organize your files. As far as Windows is concerned, drives C, D, and E are completely separate drives, even though the drives are actually just partitions on a single drive.

Linux doesn't use drive letters. Instead, Linux combines all the drives and partitions into a single directory hierarchy. In Linux, one of the partitions is designated as the root partition. The root is roughly analogous to the C drive on a Windows system. Then, the other partitions can be mounted on the root partition and treated as if they were directories on the root partition. For example, you might designate the first partition as the root partition and then mount the second partition as /user and the third partition as /var. Then any files stored in the /user directory would actually be stored in the second partition, and files stored in the /var directory would be stored in the third partition.

The directory where a drive mounts is the drive's mount point.

Notice that Linux uses regular forward-slash characters (/) to separate directory names rather than the backward-slash characters (\) used by Windows. Typing backslashes instead of regular slashes is one of the most common mistakes made by new Linux users.

While we're on the subject, Linux uses a different convention for naming files, too. In Windows, filenames end in a three-letter extension that's separated from the rest of the filename by a period. The extension is used to indicate the file type. For example, files that end in .exe are program files, but files that end in .doc are word-processing documents.

Linux doesn't use filename extensions, but periods are often used in Linux filenames to separate different parts of the name-and the last part often indicates the file type. For example, ldap.conf and pine.conf are both configuration files.