Red Hat Linux: Introduction To Linux

Welcome to Linux.

This book is about Linux, a clone of the UNIX operating system that runs on machines with an Intel 80386 processor or better, as well as Intel-compatible CPUs, such as AMD and Cyrix.

This first chapter introduces you to the major features of Linux and helps get you acquainted with them. It does not go into great detail or cover any advanced topics, as this is done in later chapters. Instead, it is intended to give you a head start in understanding what Linux is, what Linux offers you, and what you need to run it.

Don\'t be afraid to experiment. The system won\'t bite you. You can\'t destroy anything by working on it. UNIX has some amount of security built in, to prevent "normal" users (the role you will now assume) from damaging files that are essential to the system. The absolute worst thing that can happen is that you\'ll delete all of your files and have to go back and reinstall the system. So, at this point, you have nothing to lose.

One word of caution when reading this chapter: At times it will delve into topics that may seem very alien to you, especially if you are new to UNIX and Linux. Don\'t despair. As you go through this book, you will become more and more familiar with the topics introduced here. Linux is not an easy system to pick up in one day, so don\'t try to do it. There is no substitute for experience, so relax and learn Linux at your own pace.

What Is Linux?

Linux is a free, UNIX work-alike designed for Intel processors on PC architecture machines. Linux is not UNIX, as UNIX is a copyrighted piece of software that demands license fees when any part of its source code is used. Linux was written from scratch to avoid license fees entirely, although the operation of the Linux operating system is based entirely on UNIX. It shares UNIX\'s command set and look-and-feel, so if you know either UNIX or Linux, you know the other, too.

Linux supports a wide range of software, from TeX (a text formatting language) to X (a graphical user interface) to the GNU C/C++ compilers to TCP/IP networking. Linux is also compliant with the POSIX.1 standard, so porting applications between Linux and UNIX systems is a snap.

New users of UNIX and Linux may be a bit intimidated by the size and apparent complexity of the system before them. There are many good books on using UNIX out there, for all levels of expertise ranging from novice to expert. However, few (if any) of these books cover, specifically, the topic of using Linux. Although 95 percent of using Linux is exactly like using other UNIX systems, the most straightforward way to get going on your new system is with a book tailored for Linux (such as this one, amazingly enough!).

How to Pronounce Linux

Pronouncing the word Linux is one of the great controversies of the Linux world. Americans pronounce the proper name Linus with a long i sound, as in style. However, because Linux was originally based on a small, PC-based implementation of UNIX called Minix (pronounced with a short i), the actual pronunciation of Linux preserves this characteristic: It\'s officially pronounced "LIH nucks."

Linux Versus UNIX

UNIX is a trademark of X/Open. Linux is not a trademark, and has no connection to the trademark UNIX or X/Open.

UNIX is one of the most popular operating systems worldwide because of its large support base and distribution. It was originally developed as a multitasking system for minicomputers and mainframes in the mid-1970s, but it has since grown to become one of the most widely used operating systems anywhere, despite its sometimes confusing interface and lack of central standardization.

UNIX is a multitasking, multiuser operating system. This means that there can be many people using one computer at the same time, running many different applications. (This differs from MS-DOS, where only one person can use the system at any one time.)

Under UNIX, for users to identify themselves to the system, they must log in, which entails two steps: Entering your login name (the name by which the system identifies you), and entering your password, which is your personal secret key to logging in to your account. Because only you know your password, no one else can log in to the system under your username.

In addition, each UNIX system has a hostname assigned to it. It is this hostname that gives your machine a name, gives it character, class, and charm. The hostname is used to identify individual machines on a network, but even if your machine isn\'t networked, it should have a hostname.

Versions of UNIX exist for many systems, ranging from personal computers to supercomputers. Most versions of UNIX for personal computers are quite expensive and cumbersome. Where does Linux fit in? Well, Linux is free (solves the expensive part), very powerful, and easy to install and maintain by an individual (so much for the cumbersome part).

What Do I Get with a Linux System?

Linux is a freely distributable version of UNIX developed primarily by Linus Torvalds at the University of Helsinki in Finland. Linux was further developed with the help of many UNIX programmers and wizards across the Internet, allowing anyone with enough know-how and gumption to hack a custom UNIX kernel the ability to develop and change the system.

UNIX and its clones have long been perceived as large, resource-hungry, disk-devouring systems. Linux is not such a beast. It is small, fast, and flexible.

Linux has been publicly available since around November of 1991. v0.10 went out in November of 1991, v0.11 in December of 1991. There are very few small bugs now, and in its current state Linux is mostly useful for people who are willing to port code and write new code. Because Linux is very close to a reliable and stable system, Linus decided that v0.13 will be known as v0.95.

So what are some of the important features of Linux that make it so unique? Here are a few:

• Full multitasking and 32-bit support. Linux, like all other versions of UNIX, is a real multitasking system, allowing multiple users to run many programs on the same system at once. Linux is also a full 32-bit operating system, utilizing the special protected-mode features of Intel 80386 and later processors and their work-alikes.
  
  
• The X Window System. The X Window System is the de facto industry-standard graphics system for UNIX machines. A complete version of the X Window System, known as XFree86, is available for Linux. The X Window System is a very powerful graphics interface, supporting many applications.
  
  
• TCP/IP (Transmission Control Protocol/Internet Protocol) support. This is the set of protocols that links millions of university and business computers into a worldwide network known as the Internet. With an Ethernet connection, you can have access to the Internet or to a local area network from your Linux system. Using SLIP (Serial Line Internet Protocol) or PPP (Point to Point Protocol), you can access the Internet over phone lines with a modem.
  
  
• Virtual memory and shared libraries. Linux can use a portion of your hard drive as virtual memory, expanding your total amount of available RAM. Linux also implements shared libraries, allowing programs that use standard subroutines to find the code for these subroutines in the libraries at runtime. This saves a large amount of space on your system; each application doesn\'t store its own copy of these common routines.
  
  
• The Linux kernel uses no code from AT&T or any other proprietary source. Much of the software available for Linux is free. In fact, a large number of utilities in Linux are developed by the GNU project at the Free Software Foundation in Cambridge, Massachusetts. However, Linux enthusiasts, hackers, programmers, and recently even commercial companies from all over the world have contributed to the growing pool of Linux software.
  
  
• Linux supports (almost) all of the features of commercial versions of UNIX. In fact, some of the features found in Linux may not be available on other proprietary UNIX systems.
  
  
• GNU software support. Linux supports a wide range of free software written by the GNU Project, including utilities such as the GNU C and C++ compiler, gawk, groff, and so on. Many of the essential system utilities used by Linux are GNU software.
  
  
• Linux is compatible with the IEEE POSIX.1 standard. Linux has been developed with software portability in mind, thus supporting many important features of other UNIX standards.
  
  
• Virtual memory support. Linux utilizes all of your system\'s memory, without memory limits or segmentation through the use of a virtual memory manager.
  
  
• Built-in support for networking, multitasking, and other features. You\'ll see this touted as "New Technology" in systems such as Windows NT. In fact, UNIX (and now, Linux) has implemented this "new technology" for more than 15 years.
  
  
• Linux is cheaper to get than most commercially available UNIX systems and UNIX clones. If you have the patience and access to the Internet, the only price you pay for Linux is your time. Linux is freely available on the Internet. For a nominal fee of anywhere from US to US , you can save yourself some time and get CD-ROM or floppy-disk distributions from several commercial vendors (or from this book).
  
  

Arguably, the most important advantage of using Linux is that you get to work with an honest-to-goodness kernel. All of the kernel source code is available for Linux, and you have the ability to modify it to suit your needs. Looking at the kernel code is an educational experience in itself.

Undoubtedly, the development of Linux has been so rapid because of the availability of the source code. Also, with an ever-expanding group of hackers who want to get their hands dirty with their own system, Linux has grown steadily into the fully packed operating system that it is today.

Hardware Requirements

Now that you know a little about the good and bad points of Linux, let\'s see what\'s required in terms of hardware.

Unlike some other versions of UNIX for the PC, Linux is very small. You can run an entire system from a single, high-density 5.25-inch floppy. However, to run a complete Linux system, there are other hardware requirements.

Linux, by its very nature, is continuously expanding, and more features are added every day. However, hardware compatibility is limited to that hardware the developers themselves have access to. For instance, if none of the Linux developers has access to the WhizBang Slice-O-Matic T3222 Ethernet card from a no-name manufacturer, then chances are it isn\'t supported.

On the other hand, there are many generic drivers for hardware, such as the IDE disk driver, which should work with all IDE hard drives and adapters regardless of manufacturer. Of course, the developers of the drivers couldn\'t test their software against every IDE device on the market, so they assume the IDE standards are followed by manufacturers. If a device doesn\'t work, it\'s probably because the manufacturer deviated from the standards, or added features the generic drivers can\'t handle.

A good place to look on the CD-ROM is in the /docs/howto directory for the Hardware-HOWTO file. This file will list a lot of the supported hardware for Linux.

If your favorite peripheral isn\'t supported by Linux, all that\'s required is to write a kernel driver for it. This may be easy or difficult, depending on the hardware and the technical specifications that are available. For example, some hardware developers prefer to write their own drivers for MS-DOS and Windows, and not release specifications for third parties to write their own. Therefore, writing drivers for Linux will be difficult, if not impossible.

The following is a rough guideline of some hardware requirements for Linux. You do not have to follow them directly, but this list should give you a rough idea of what\'s required:

• An Intel 80386 or better CPU (the faster and more powerful the better, of course). You don\'t need a math coprocessor, although it\'s strongly recommended as it speeds up a lot of graphics operations, especially under X. If you have an 80386 chip, 80387 math coprocessors are available separately and are installed in a socket on your motherboard. If you have a 80486 processor, the math coprocessor is on the 486 chip itself. (The exception is the 80486SX, which is a 486 chip without the coprocessor components.) Pentium and Pentium Pro CPUs have the coprocessor built in.
  
  
• If you don\'t have a math coprocessor, the Linux kernel will emulate floating-point math for you. If you do have one, however, floating-point math will be handled by the hardware, which for some applications is a real plus.
  
  
• Your system must be either an ISA, EISA, PCI, or local bus architecture machine. These terms specify how the CPU communicates with hardware, and are a characteristic of your motherboard. Most existing systems use the ISA bus architecture.
  
  

• At least 4MB of RAM.
  
  
• Memory is speed, so if you have more RAM you\'ll thank yourself for it later. If you\'re a power user, 8MB should be more than enough for most applications. If you want to run X Window, your system will require at least 8MB of RAM.
  
  
• A hard drive with space available for installing Linux. The amount of space required depends on the amount of software you\'re installing and how much free space you wish to leave yourself. You can install Linux in very small amounts of disk space, but a realistic minimum is about 150MB. For a full system with X and development tools, much more is required. The complete installation can use up 250MB, with more useful for data files.
  
  
• A Hercules, CGA, EGA, VGA, or Super VGA video card and monitor. In general, if your video card and monitor work under MS-DOS or Microsoft Windows, then Linux should be able to use them without any problem. However, if you\'re going to use the X Window system (either Metro-X or Xfree86), some video configurations are not supported.
  
  

Other Hardware Requirements

Linux will also run on a number of laptop machines (some laptops use certain software interrupts to power the memory, and Linux doesn\'t work well with these systems to date). The best way to find out if Linux will run on your hardware is just to try it out.

There are other hardware drivers currently under development for Linux. To use these drivers, however, you usually have to patch them into your kernel code, which assumes that you already have a running Linux system (a kind of chicken-and-egg problem if you have not already installed Linux). In such cases, you can install whatever Linux you happen to have and then apply the patches with the Linux patch command.

Then there is the issue of tape drives for Linux. There is a working QIC-02 device driver for Linux, supporting Everex/Wangtek cards. There are additional patches for the QIC-02 to support Archive SC402/499R. You can find them in /pub/linux/alpha/qic-02 directory at tsx-11.mit.edu server. (There have been reports of some bugs in the driver, but you can back up and restore.)

Most of the newer tape drivers are all for SCSI drives, so if you have a SCSI tape drive, chances are that it is supported.