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August 14, 2016 21:40-22:10

1.3 FRICTION BETWEEN UNIX AND LINUX

1.3 friction between UNIX and Linux

Because they are similar, this book covers both UNIX and Linux systems. Unfortunately, mentioning UNIX and Linux together in the same sentence can sometimes be like stepping into a political minefield, or perhaps blundering into a large patch of quicksand. But since the relationship between UNIX and Linux seems to engender some confusion as well as animosity, it's hard to avoid staking out a position. Here is our perspective and our short version of the facts.

Because UNIX and Linux systems are quite similar, this book will explain the management of both systems. Unfortunately, using both UNIX and Linux in one sentence is like stepping into a political whirlpool, or perhaps a big quagmire. However, since the relationship between UNIX and Linux seems to show some confusion and conflict, it is difficult to avoid not talking about our position. Here are our views, as well as our brief account of the facts.

Linux is a reimplementation and elaboration of the UNIX kernel. It conforms to the POSIX standard, runs on several hardware platforms, and is compatible with most existing UNIX software. It differs from many-but not all-variants of UNIX in that it is free, open source, and cooperatively developed. Linux includes technical advances that did not exist in UNIX, so it is more than just a UNIX clone. At the same time, traditional UNIX vendors have continued to refine their systems, so there are certainly areas in which commercial UNIX systems are superior to Linux.

Linux reimplements and optimizes the UNIX kernel. Linux follows the POSIX standard, can run on several hardware platforms, and is compatible with most existing UNIX software. Unlike most (but not all) other UNIX variants, it is free, open source, and developed by the selfless contributions of hundreds of different individuals and organizations. At the same time, traditional UNIX vendors continue to improve their systems, so there must be areas where commercial UNIX systems are better than Linux.

Whatever the relative merits of the systems, Linux is a legally, developmentally, and historically distinct entity that cannot properly be referred to as "UNIX" or as a "version of UNIX." To do so is to slight the work and innovation of the Linux community. At the same time, it's somewhat misleading to insist that Linux is "not UNIX." If your creation walks like a duck and quacks like a duck, you may have invented a duck.

Regardless of the relative advantages and disadvantages of the two systems, Linux is legally, developmentally, and historically distinct from UNIX, so you can't call Linux UNIX, or a version of UNIX. Doing so ignores the work and innovation done by the Linux community. At the same time, it would be a bit misleading to insist that Linux is not UNIX. If something made walks like a duck and barks like a duck, it may be said that it is a duck! This means that just because Linux is like UNIX, you can't think of Linux as UNIX.

August 15, 2016 15:20-16:20

Schisms exist even within the Linux camp. It has been argued, with some justification, that referring to Linux distributions simply as "Linux" fails to acknowledge the work that went into the software that runs outside the kernel (which in fact constitutes the vast majority of software on an average system). Unfortunately, the most commonly suggested alternative, GNU/Linux, has its own political baggage and has been officially endorsed only by the Debian distribution. The Wikipedia entry for "GNU/Linux naming controversy" outlines the arguments on both sides.1 Interestingly, the use of open source software is now predominant even on most UNIX systems, but no one seems to be pushing for a GNU/UNIX designation just yet.

Even in the Linux camp, there are divisions. It has been proved that if the Linux distribution is referred to as "Linux" for short, it is not recognized that developers work on software that runs outside the kernel (which is actually a large part of the software on a typical system). Unfortunately, the most commonly recommended alternative title, "GNU/Linux", also has its own political baggage, so only the distribution of Debian officially adopted it. The Wikipedia entry on the "GNU/Linux naming dispute" lists the arguments of both sides of the dispute. Interestingly, today, even on most UNIX systems, the use of open source software dominates, but no one has mentioned the term "GNU/Linux".

Linux software is UNIX software. Thanks largely to the GNU Project, most of the important software that gives UNIX systems their value has been developed under some form of open source model The same code runs onLinux and nonLinux systems. The Apache web server, for example, doesn't much care whether it's running on Linux or Solaris. From the standpoint of applications and most administrative software, Linux is simply one of the best-supported and most widely available varieties of UNIX.

Linux software is UNIX software. Thanks to the GNU project, most of the important software that makes UNIX systems more valuable is developed in some form of open source code. The code that runs on Linux and non-Linux systems is the same. For example, the Web server Apache doesn't care whether it runs on Linux or HP-UX. In terms of the role of the application, Linux is just one of the best supported UNIX variants.

It's also worth noting that Linux is not the only free UNIX-like operating system in the world. OpenSolaris is free and open source, although its exact licensing terms have earned suspicious looks from some open source purists. FreeBSD, NetBSD, and OpenBSD-all offshoots of the Berkeley Software Distribution from UC Berkeley-have ardent followers of their own. These OSes are generally comparable to Linux in their features and reliability, although they enjoy somewhat less support from third-party software vendors.

It is also worth mentioning that Linux is not the only free UNIX version in the world today. OpenSolaris is also free and open source, although in the eyes of some people who advocate pure open source, its license terms are questionable. FreeBSD, NetBSD, and OpenBSD-- are all offshoots of BSD (Berkeley Software Distribution, or Berkeley Software Distribution) at UC Berkeley-each with its own dedicated followers. Although these operating systems receive little support from third-party software vendors, they are often comparable to Linux in terms of functionality and reliability.

UNIX and Linux systems have both been used in production environments for many years, and they both work well At this point, the choice between them has more to do with packaging, support, and institutional inertia than any real difference in quality or modernity.

UNIX and Linux systems have been used in production environments for many years, and they both perform well. Now it's time to choose between them, thinking more about the software packaging mechanism, the support available, and the inertia of usage habits, rather than the actual differences in quality or maturity.

In this book, comments about "Linux" generally apply to Linux distributions but not to traditional UNIX variants. The meaning of "UNIX" is a bit more fluid, as we occasionally apply it to attributes shared by all UNIX derivatives, including Linux (e.g.UNIX file permissions). To avoid ambiguity, we usually say "UNIX and Linux" when we mean both.

The book's comments on "Linux" generally apply to a variety of Linux distributions, but not to traditional UNIX variants. The meaning of "UNIX" is a little more varied, because we occasionally use it on attributes common to all UNIX variants, including Linux (for example, "UNIX file permissions"). To avoid confusion, we usually say "UNIX and Linux" when we want to express both.

August 16, 2016 16:50-17:20

1.4 LINUX DISTRIBUTIONS

1.4 release of Linux

All Linux distributions share the same kernel lineage, but the ancillary materials

That go along with that kernel can vary quite a bit. Distributions vary in their

Focus, support, and popularity. There continue to be hundreds of independent Linux distributions, but our sense is that distributions based on the Debian, Red Hat, and SUSE lineages will continue to predominate in production environments over the next five years.

All Linux distributions share the same kernel source, but the assistive software that comes with the kernel varies greatly from distribution to distribution. Each release varies in its focus, support, and popularity. There are still hundreds of independent Linux distributions in terms of data, but we feel that over the next five years, those based on Debian,Red Hat and SUSE sources will dominate the production environment.

The differences among Linux distributions are not cosmically significant. In fact

It is something of a mystery why there are so many different distributions, each

Claiming "easy installation" and "a massive software library" as its distinguishing features. It's hard to avoid the conclusion that people just like to make new Linux distributions.

There are differences between Linux distributions, but not to such an extent that they are far apart. In fact, it's hard to explain why there are so many different distributions, each featuring "easy to install" and "massive software libraries". So it's hard to come to the conclusion that people just like to "do" a new Linux release.

Many smaller distributions are surprisingly competitive in terms of fit and finish.

All major distributions, including the second tier, include a relatively painless installation procedure, a well-tuned desktop environment, and some form of package management. Most distributions also allow you to boot from the distribution DVD, which can be handy for debugging and is also a nice way to take a quick look at a new distribution you are considering.

Many smaller distributions are highly competitive in terms of maturity and completeness. All major distributions, including second-tier ones, have fairly easy installation steps, a well-provisioned desktop environment, and some form of package management mechanism. Most distributions also allow users to boot directly from the DVD CD, which is convenient for debugging and a good way to quickly learn about new distributions that follow.

Since our focus in this book is the management of large-scale installations, we're

Partial to distributions such as Red Hat Enterprise Linux that take into account

The management of networks of machines. Some distributions are designed with

Production environments in mind, and others are not. The extra crumbs of assistance that the production-oriented systems toss out can make a significant difference in ease of administration.

Since we focus on the management of large-scale installations in this book, we will focus on distributions such as RHEL (Red Hat Enterprise Linux) for managing computer networks. Some distributions are designed to take into account the production environment, while others do not. The additional support provided by the system for the production environment makes a huge difference for the convenience of system management.

When you adopt a distribution, you are making an investment in a particular vendor's way of doing things. Instead of looking only at the features of the installed software, it's wise to consider how your organization and that vendor are going to work with each other in the years to come.

When users adopt a distribution, they invest in the way a particular publisher does things. Don't just look at the features after the software is installed, but knowingly consider that your unit and that publisher will work together in the coming data years.

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