UNIX(R) for Dummies

Yeah, we know that it's pronounced "linn-ux" or "leen-ux," not "line-ux," but it still needs taming, and if you look around the office and find nobody other than yourself to fix things, you're the Linux tamer.

Using Linux is no different from using any other type of UNIX, as long as it's on someone else's computer and they have set you up with an account. When your computer is running Linux, however, and you are responsible for maintaining it, things become much more complicated. Although we have no way to teach all the complexities of UNIX system administration in a book like this one, we can describe a few key points to get you started.

LINUX^® For Dummies^®, 2nd Edition, by Craig Witherspoon, Coletta Witherspoon, and Jon Hall (published by IDG Books Worldwide, Inc.) is a great introduction to Linux and Linux administration. Running Linux, by Welsh and Kaufman (published by O'Reilly & Associates), has most of the information you need to really administer a Linux system. Also, the World Wide Web is awash in sites devoted to Linux. A good place to start is the Linux home page, at http://www.linux.org/. (See Chapter 18 for more information about the World Wide Web if you're uncertain what it means.) Chapter 27 of this book lists a number of other places to go Linux hunting on the World Wide Web.

The root of all UNIX

UNIX is a multiuser world: Lots of people can use the computer at the same time, by connecting from remote locations. The first thing you need to know about administering a Linux system is the difference between the user called root and every other user. Root (also grandly called the superuser) is the system administrator. This account has all the privileges to change things on the system. If you want to add users, install some software, or even turn off the computer, you must be logged in as root. If you're logged in as someone other than root and you try to do anything related to system administration, your computer responds with a barrage of "permission denied" messages. It's nothing personal. It's just the computer's way of telling you that in a multiuser environment, it doesn't want just anyone messing around with it -- only the one person it trusts, which is root.

"Fine," you say. "I'll just log in as root all the time and not have to worry about running into those pesky permission problems." Bad idea! Using the root account to do non-system-administration tasks is dangerous because sometime -- eventually, when you least expect it -- you type a command you really didn't want to -- oh, say, deleting all the files on the hard disk (it happens more frequently than you may think). If you're logged in as someone other than root, the computer replies with a simple "permission denied." If you're root, though, the damage is done, and UNIX does not have an "undelete" command! Remember that permissions are your friends!

Adding a user

Assuming that you're convinced about not logging in as root unless you really must, you have to add a user account for yourself (or for others) to use for everyday tasks. Suppose that you want to create the username "bobbyjoe" for yourself. To add this user, log in as root (because adding users is one of those special, privileged tasks that only root can perform) and type the command adduser bobbyjoe. The computer creates the new user and then, if you're lucky, reminds you to set the password for the new user. Whether or not the computer reminds you, you have to add the password by typing passwd bobbyjoe. Then enter the password when the computer asks for it. It asks you to enter it twice, just to make sure that you typed it correctly.

With some versions of Linux, your computer gives you remedial password advice if it thinks that you need it. If you create a user named noah and then try to add the password ark, your computer may say BAD PASSWORD: It's WAY too short. If you try to fake the computer out by adding the password arkarkark, it may say BAD PASSWORD: it does not contain enough DIFFERENT characters. If you're not sure what constitutes a good password, go back and read the section in Chapter 1 about password smarts. As a system administrator, you're responsible for the security of the system, so don't say that you haven't been warned.

How do I turn this thing off?

UNIX is very sensitive to impolite treatment on the part of the operator. If you just log out and turn off the machine with the power switch, UNIX reminds you of this rude treatment with a flood of error messages when you next restart the computer. To turn the machine off, you first must execute the shutdown command. While logged in as root, enter the command shutdown now to turn the machine off gracefully. If other users are logged in and you want to give them some warning, you can type the number of minutes until shutdown: shutdown +10, for example, waits ten minutes before shutting down and warns any users who are logged in. To reboot the computer, shutdown -r now (-r for reboot) shuts down the machine and then restarts it. Some Linux systems also let the "three-finger salute" (Ctrl+Alt+Del, familiar to DOS and Windows users) serve as a shortcut for shutdown -r now.

Users who bring experience with other flavors of UNIX to their first encounters with Linux will probably find it relatively easy to get Linux up and running. The large (and growing) community of Windows users who want to add or switch to Linux will likely encounter some fairly rough sledding.

One of the great things about Linux is that it can run on PCs with Intel chips in them. Disgruntled Windows users can therefore switch to Linux without having to buy a new computer. Windows users who are still sufficiently gruntled can check out Linux by installing it, cheek by jowl, on the same computer with Windows (as long as it has enough free disk space, of course).

All well and good, in theory. In practice, however, you can get yourself into trouble with startling efficiency. Even if it's going to coexist on your computer with Windows, Linux needs its own separate file system, which in turn needs its own separate area of your computer's disk. These separate areas are called partitions, or drives, and you have to have at least two partitions, one for Windows and one for Linux, to get Windows and Linux to live together in peace and harmony.

If you have only one big drive or partition on your computer, you have to create a second partition before you can even begin installing Linux. To do so, you have to run a DOS utility named fdisk on your computer. The trouble with fdisk is that if you make one false move, everything that's already on your computer gets wiped out, no questions asked. If you already have Windows installed on your computer, do yourself a favor and back up your system before even thinking about using fdisk . Then carefully follow whatever instructions you have for setting up a computer that can run both Windows and Linux (known as a dual-boot system). LINUX For Dummies, 2nd Edition (mentioned earlier in this chapter), for example, describes the whole process in gory detail.

Complete Linux systems are packaged into "distributions," which describe not how Linux is distributed but rather how the operating system and the GNU programs are bundled. A few distributions are in common use: Slackware, Red Hat, Caldera, and Debian. All are available for free via the Internet or for a small charge on CD-ROM. As a user, it doesn't matter which distribution you use because they all behave in much the same way. As a system administrator, though, you should consider the important differences the distributions have among them.

Slackware, the oldest of the three, has been around since the beginning of Linux. It is the most "traditional" distribution (traditional in the UNIX sense, as in not particularly user-friendly) and has little in the way of utilities to facilitate the management of a Linux system. For this reason, it tends to be favored by those who have been around UNIX systems for a while.

Red Hat Linux is the most popular distribution. It features plenty of tools to make the life of a system administrator easier, most notably the Red Hat Package Manager (RPM), which eases the installation, upgrade, and deletion of software packages, and even the operating system itself. Recently, Red Hat began adding all sorts of extras to its CD distribution. For about $50, you can get the Netscape Communicator Web browser, the latest version of the WordPerfect word processing package, and a whole stack of graphical applications known as ApplixWare.

The Debian and Caldera OpenLinux distributions, like Red Hat, also provide interfaces that ease the task of a system administrator. Although these distributions are not now as popular as Slackware or Red Hat, their popularity is growing quickly. OpenLinux, probably because of its aggressive marketing campaign, is beginning to give Red Hat a run for its money.

The freely available, "alternative" image of Linux discouraged commercial enterprises from adopting Linux in its early days. Understandably, many companies did not want to deal with an operating system that did not have a corporate entity standing behind it, no matter how reliable or trouble-free the product. To fill this need, a number of companies have stepped in to provide commercial support for Linux. Red Hat Software, Inc., for example, provides a commercial version of its Linux distribution in addition to the free version. Organizations that purchase the commercial Red Hat distribution can therefore turn to Red Hat for support rather than (or in addition to) Usenet. Caldera, Inc., also provides support for commercial users. Purchasers of the Caldera OpenLinux package get user support from Caldera as well as for some additional commercial software packages that Caldera includes.

If you enjoy editing lots of configuration files and moving them around "by hand," the old-fashioned way (believe it or not, some people like to do it that way), you should go with Slackware. Everyone else will find life easier with Red Hat, Debian, or Caldera.

Many other Linux distributions are out there, of course, so you may want to do a little more investigating before deciding on a package:

• DLX Linux and hal91 Floppy Linux: For PC users without much free space, these packages offer distributions that fit on a single floppy disk.
• Linux Pro: On the other end of the spectrum, it comes complete with seven CDs and a 1,600-page encyclopedia of reference information.
• LinuxPPC: It's specifically designed to run on PowerPCs.
• LinuxWare: LinuxWare targets the Windows audience by enabling users to start the installation from within Windows 95.
• S.u.S.E. Linux: Comes with all kinds of preconfigured software packages, X servers, and graphical utilities for novice users.

What happens when you have a problem with Linux? (It has been known to happen.) If you've shelled out for a commercially distributed CD version, you get possibly a few months of free support if the company has the wherewithal to offer it. Otherwise, no technical-support hotline exists to call when things go wrong.

A huge base of Linux users around the world does exist, though, most of whom have access to the Internet. Usenet is the best place to find help with Linux, as described in Chapter 19. For someone accustomed to calling a commercial entity on the phone for tech support, the idea of posting questions on Usenet may seem foreign, even hopelessly naive. Questions are generally read by so many thousands of people, though, that the odds are overwhelming that someone familiar with your problem will read the question and respond, usually within a day or so. (In fact, many people claim that Usenet-based support is faster and more reliable than some technical-support hotlines!) The Linux community as a group still maintains an attitude of "we're all in this together," and the Usenet support system has mostly worked. The Linux groups, which tend to be some of the most active computer groups on all of Usenet, are listed at the end of Chapter 27.