Part I

CHAPTER 1

Introduction to Red Hat Linux and UNIX

IN THIS CHAPTER

• Advantages of Linux 5
• Copyright and Warranty 7
• Where to Get Red Hat Linux 7
• System Requirements 7

UNIX, not to be confused, as Dilbert's boss once did, with a eunuch, is one of the most popular operating systems in the world. It is a trademark of The Open Group, but was originally developed by AT&T. UNIX is a real operating system. A real operating system has, as a minimum, two qualifications: more than one person can access the computer at the same time and, while doing so, each person can run multiple applications. This is called being a multiuser and multitasking operating system. UNIX was originally designed to be such a multitasking system back in the 1970s, running on mainframes and minicomputers.

With UNIX, each user logs in using a login name. Optionally (and highly recommended), the user must also supply a password. The password ensures that the person logging on with the user login name is really who he or she claims to be. Users don't just log in to any no-name computer, either. Each computer has a "personality," if you will, which, at a minimum, is a hostname (mine is Lolly). If the computer is attached to a network, it will have several other identifying items, including, but not limited to, a domain name and an IP address.

UNIX will run on just about every platform made. Many vendors purchased the source code and have developed their own versions. The various vendors (IBM, Hewlett-Packard, Sun, and so on) have added their own special touches over the years. But they are not the only ones to further modify UNIX. When UNIX was first developed, the source code was given out freely to colleges and universities. Two schools, University of California at Berkeley and Massachusetts Institute of Technology, have been on the front edge of development since the beginning.

As you can imagine, the UNIX development went haywire. People all over the globe began to develop tools for UNIX. Unfortunately, there was no coordination to guide all the development. This caused a lot of differentiation between the different versions of UNIX. Finally,
standards started to appear. For UNIX, many of the standards fall under the IEEE POSIX.1 standard.

The downside of UNIX is that it is big. It is also expensive, especially for a PC version. This is where Linux comes in. Linux, as explained in a little more detail later in this chapter, was designed to be small, fast, and inexpensive. So far, the designers have succeeded.

Linux was originally created by Linus Torvalds of the University of Helsinki in Finland. Linus based Linux on a small PC-based implementation of UNIX called minix. Near the end of 1991, Linux was first made public. In November of that same year version 0.10 was released. A month later, in December, version 0.11 was released. Linus made the source code freely available and encouraged others to develop it further. They did. Linux continues to be developed today by a world-wide team, led by Linus, over the Internet.

The current stable version of Linux is version 2.0. Linux uses no code from AT&T or any other proprietary source. Much of the software developed for Linux is developed by the Free Software Foundation's GNU project. Linux, therefore, is very inexpensive; as a matter of fact, it is free (but not cheap).

Advantages of Linux

So, why would you choose Linux over UNIX? As already mentioned, Linux is free. Like UNIX, it is very powerful and is a "real" operating system. Also, it is fairly small compared to other UNIX operating systems. Many UNIX operating systems require 500MB or more, whereas Linux can be run on as little as 150MB of space, and it can run on as little as 2MB of RAM. Realistically, though, you will want to have room for development tools, data, and so on, which can take up 250MB or more, and your RAM should be 12_16MB (although the more, the merrier!). Here's what you get in exchange for that valuable space:

• Full multitasking—Multiple tasks can be accomplished and multiple devices can be accessed at the same time.
• Virtual memory—Linux can use a portion of your hard drive as virtual memory, which increases the efficiency of your system by keeping active processes in RAM and placing less frequently used or inactive portions of memory on disk. Virtual memory also utilizes all your system's memory and doesn't allow memory segmentation to occur.
• The X Window System—The X Window System is a graphics system for UNIX machines. This powerful interface supports many applications and is the standard interface for the industry.
• Built-in networking support—Linux uses standard TCP/IP protocols, including Network File System (NFS) and Network Information Service (NIS, formerly known as YP). By connecting your system with an Ethernet card or over a modem to another system, you can access the Internet.
• Shared libraries—Each application, instead of keeping its own copy of software, shares a common library of subroutines that it can call at runtime. This saves a lot of hard drive space on your system.
• Compatibility with the IEEE POSIX.1 standard—Because of this compatibility, Linux supports many of the standards set forth for all UNIX systems.
• Nonproprietary source code—The Linux kernel uses no code from AT&T, nor any other proprietary source. Other organizations, such as commercial companies, the GNU project, hackers, and programmers from all over the world have developed software for Linux.
• Lower cost than most other UNIX systems and UNIX clones—If you have the patience and the time, you can freely download Linux off the Internet. Many books also come with a free copy. (This book includes it on CD-ROM.)
• GNU software support—Linux can run a wide range of free software available through the GNU project. This software includes everything from application development (GNU C and GNU C++) to system administration (gawk, groff, and so on), to games (for example, GNU Chess, GnuGo, NetHack).