Linux System Administration: A User's Guide [Paperback]

The definitive, real-world guide to Linux system administration!
Hands-on, example-rich coverage for sys admins at all levels, using any leading distribution.
Installation, user management, monitoring, printing, security, and more.
By Marcel Gagné, well-known Linux Journal "Cooking with Linux" and Sys Admin columnist. Respected Linux Journal and Sys Admin columnist Marcel Gagné has written the definitive guide to Linux system administration- a book that will be invaluable for sys admins at all levels of experience, using any leading distribution. Linux System Administration offers hands-on, results-focused coverage of every key Linux configuration and management task. Gagné offers detailed coverage of installation, Linux file management tools and file naming conventions; disks and file systems; users and groups; hardware; X-based graphical desktops; networking; kernel building; printing; and much more. The book contains practical guidance on scripting and automating administration tasks; administration tools; Internet services; security; tuning; and more. Gagné goes far beyond the basics, offering expert guidance on becoming a smarter sys admin -- from avoiding problems to tracking trouble calls and identifying resources that can provide the solutions you need. The book concludes with a series of instant-reference "cheat sheets" designed to help sys admins get the most common jobs done fast. For everyone responsible for administering Linux systems, including both experienced and new sys admins, as well as those migrating from UNIX or Windows environments. Also for power users, and any user or administrator who must maximize the security of their Internet-connected workstations.
Marcel Gagné is President of Salmar Consulting, a Canadian consulting company specializing in UNIX/Linux systems integration. He previously served as a system administrator for both Dynix and Honeywell, utilizing AIX, HP-UX, BSD, and Windows NT. He has installed and verified firewalls and web servers for many large and small clients. He is a regular contributor to both Linux Journal and Sys Admin.

What Is Linux?

My guess is that if you are reading this book, you already know the answer to that question. You already know that Linux is a fully multitasking operating system based on UNIX.

You may even be aware of this now famous (perhaps legendary) Usenet message from Linus Torvalds to the Usenet group comp.os.minix:

From: torvalds@klaava.Helsinki.FI (Linus Benedict Torvalds) Newsgroups: comp.os.minix
Subject: What would you like to see most in minix?
Summary: small poll for my new operating system
Message-ID: Date: 25 Aug 91 20:57:08 GMT Organization: University of Helsinki
Hello everybody out there using minix -

I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since april, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).

I've currently ported bash(1.08) and gcc(1.40), and things seem to work. This implies that I'll get something practical within a few months, and I'd like to know what features most people would want. Any suggestions are welcome, but I won't promise I'll implement them :-)

Linus (torvalds@kruuna.helsinki.fi)

PS. Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT protable (uses 386 task switching etc), and it probably never will support anything other than AT-hard disks, as that's all I have :-(.

We've come a long way from Linus's original vision of what his little project would and would not accomplish. What he managed to do was capture the imagination of scores of talented programmers around the world. Joined together through the magic of the Internet, they collaborated, coded, tweaked, and gave birth to the operating system that is now revolutionizing the world of computing.

Notice I mentioned "scores of talented programmers." Linux is not the work of one man alone. Linus Torvalds is the original architect of Linux, its father if you will, but he is not the only effort behind it. Perhaps Linus Torvalds' greatest genius lay in knowing when to share the load. For no other pay but satisfaction, he employed people around the world, delegated to them, worked with them, and asked for and accepted feedback in a next generation of the model that began with the GNU project.

GNU, by the way, is a recursive acronym that stands for "GNU's Not Unix," a project of the Free Software Foundation. This project was started in 1984 with the intention of creating a free, UNIX-like operating system. Over the years, many GNU tools were written and widely used by many commercial UNIX vendors and, of course, system administrators trying to get a job done. The appearance of Linus Torvalds' Linux kernel had made the GNU dream of a completely free, UNIX-like operating system a reality at last.

Why Linux?

Because this book is not so much about getting and installing Linux as it is working with Linux, I won't spend a long time answering the question "Why Linux?" Frankly, it would take much less time to answer the question "Why not Linux?" Suffice it to say that Linux is a powerful, reliable (some, including your humble author, might even say it's rock solid), expandable, flexible, configurable, multiuser, multitasking, and completely free operating system that runs on numerous hardware offerings. These hardware offerings include X86 chipsets (your basic, run-of-the-mill Intel PC), DEC Alpha, Macintosh, PowerPC, and a growing number of embedded processors. You can find Linux in PDA organizers, digital watches, golf carts, and cell phones. In fact, Linux has a greater support base (in terms of platforms) than just about any other operating system you can think of. IBM's entire line of hardware runs Linux!

Completely free?

Hmm . . . Maybe I should explain "free." Free, in this case, isn't a question of cost, although you can get a free/gratis copy of Linux and install it on your system without breaking any laws. Of course, because "there ain't no such thing as a free lunch" (to quote Robert A. Heinlein), even a free download costs you connection time on the Internet, disk space, time, and so on.

Linux is distributed under the GNU General Public License (GPL), which in essence says that anyone may copy, distribute, and even sell the program so long as changes to the source are reintroduced back to the community and the terms of the license remain unaltered. Free means that you are free to take Linux, modify it, and create your own version. Free means that you are not at the mercy of a single vendor who forces you into a kind of corporate servitude by making sure that it is extremely costly to convert to another environment. If you are unhappy with your Linux vendor or the support you are getting, you can move to the next vendor without forfeiting your investment in Linux.

The GNU GPL permits a distributor to "charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee." This is further qualified by the statement that the distributor must release "for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code." In other words, the GPL ensures that programs like Linux will at best be free of charge. At worst, you may be asked to pay for the cost of a copy.

Everyone should take some time to read the GNU GPL. You'll find a link to its home in the Resources section at the end of this chapter.

The System Administrator's Job

So, this book is about Linux system administration. Just what the heck is system administration anyway? System (or systems) administration is a strange beast. After many years of administering literally hundreds of computer platforms running different operating systems and varying in complexity, I came to have what some might call a strange idea of this job description.

system administrator n. Part magician, part juggler, part technical support analyst, and part bartender/psychoanalyst, the system administrator performs the impossible job of keeping all members of his or her company satisfied by making sure that everything works. This usually includes things that are completely outside the system administrator's control, such as telephones, photocopiers, fax machines, heating, air conditioning, and paper shortages in the supply cabinet.

I'm being a little silly, I realize, but system administrators get to their exulted position through the strangest of ways. You will find the career system administrator who actually wanted to do the job and worked his or her way to that goal. Along this path, you will also find secretaries who were unfortunate enough (or foolish enough) to say they knew something about computers and were instantly cast into the role. This latter category of sysadmin (a popular shortening of "system administrator") is more common than you can possibly imagine. Finally, you have the home user, a relative newcomer to this wonderful calling, thanks in large part to Linux.

About This Book

When I first started thinking about how I would lay out this book, I considered a number of approaches and settled on the following. I don't want to bore you, the reader, with chapters of references to HOWTOs on the Internet (although I will give you appropriate resource links when necessary). Nor do I want to give you verbatim listings of command options or man pages.

What I do want to do is give you real-life examples and things that you can try yourself to get the most out of your system. You will get the theory as well, but only so much. I want you to walk away with an understanding that only comes from actually doing things. The most fun I have ever had in the computer biz came from doing things, trying things out, and basically just playing. Computers can be fun, even when you are working instead of playing games. This is cool stuff. Imagine--a machine that does what you tell it to do! When the printer is jammed up and your connection to the Internet is down, you tend to forget how marvelous all this really is. So, saddle up to your keyboard, pour yourself a cup of java (that's coffee, not the programming language), limber up those fingers, and start playing.

An assumption I've decided to make is that you already have a Linux system to work with. What you want to know is how to work with it better. This doesn't mean I intend to skimp on anything. I will compare various installation philosophies and distributions so that you can satisfy your curiosity about other Linuxes. Which provides me with the perfect segue into another assumption I've decided to make.

Linux is an operating system kernel supported and bundled into an operating system distribution, which is then marketed, sold, or given away by many different companies or organizations. What this means is that I will try to cover the quirks related to various distributions that may affect you when you try out the things you read in this book. I can't promise that I'll cover every possible distribution here, but what I will do is give you the tools to discover where your version of a particular configuration file or script fits into your system so that you can at least find it. Suffice it to say that even in cases of "my file was here rather than there," the formats, at least, will tend to be constant.

0201719347P09242001

"Gagne is clearly an insider in the Linux community, familiar with both the technical details and the culture, which sets this book apart from others in the field."

--Joseph Sloan, Lead System Administrator, Mirai Consulting

This comprehensive, hands-on guide to Linux system administration provides you with the deeper understanding of the inner workings of Linux and the pragmatic techniques you need to become an outstanding Linux system administrator--whether you are a career administrator in a corporate environment or simply administering your home system.

Written both for those who are new to Linux and those who are already proficient and wish to hone their skills, Linux System Administration starts with the basics and builds up to more sophisticated material.

You will find complete coverage of all major system administration topics:

• Linux versus UNIX
• Installation tips and tricks
• Working effectively with the Linux command line
• Organizing and working with system users
• Disks, file systems, backup, and restore
• The inner workings of X and the graphical desktop
• Configuring and using scanners, CD-Recordables, and other devices
• Internet connectivity
• Finding, building, and installing software
• Kernel building and renovation
• Scripting and automation
• Network administration, electronic mail, and Web services
• Integrating Windows with Linux
• System logs and accounting
• Security and firewalls
• Performance monitoring and tuning

Using standard Linux tools (PostgreSQL, Apache, Perl, and more) this book will help you deploy a feature-rich corporate intranet featuring online discussion groups, bulletin boards, a company phone directory, and a document center. You will also learn everything you need to know to install a complete electronic mail and Internet gateway solution for your home or office on a single, shared connection. In addition, numerous anecdotes from the trenches, examples of techniques to try, and plenty of experience-based advice bring important concepts to life.

Written with good humor and enthusiasm for the profession of system administration, as well as a deep appreciation for the power and flexibility of Linux, Linux System Administration will teach you the tricks of the trade, guide your efforts, and serve as a definitive and comprehensive reference.

0201719347B09242001

Marcel Gagné is best known as author of the Linux Journal's "Cooking with Linux" series, which has earned the magazine's Readers' Choice award for favorite column four years in a row, and as the regular "Linux Guy" on G4/TechTV Canada. His books include Moving to the Linux Business Desktop and Linux Administration: A User's Guide (both from Addison-Wesley.) He is one of the Linux world's most familiar and respected voices.

What Is Linux?

My guess is that if you are reading this book, you already know the answer to that question. You already know that Linux is a fully multitasking operating system based on UNIX.

You may even be aware of this now famous (perhaps legendary) Usenet message from Linus Torvalds to the Usenet group comp.os.minix:

From: torvalds@klaava.Helsinki.FI (Linus Benedict Torvalds) Newsgroups: comp.os.minix
Subject: What would you like to see most in minix?
Summary: small poll for my new operating system
Message-ID: <1991Aug25.205708.9541@klaava.Helsinki.FI> Date: 25 Aug 91 20:57:08 GMT Organization: University of Helsinki
Hello everybody out there using minix -

I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since april, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).

I've currently ported bash(1.08) and gcc(1.40), and things seem to work. This implies that I'll get something practical within a few months, and I'd like to know what features most people would want. Any suggestions are welcome, but I won't promise I'll implement them :-)

Linus (torvalds@kruuna.helsinki.fi)

PS. Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT protable (uses 386 task switching etc), and it probably never will support anything other than AT-hard disks, as that's all I have :-(.

We've come a long way from Linus's original vision of what his little project would and would not accomplish. What he managed to do was capture the imagination of scores of talented programmers around the world. Joined together through the magic of the Internet, they collaborated, coded, tweaked, and gave birth to the operating system that is now revolutionizing the world of computing.

Notice I mentioned "scores of talented programmers." Linux is not the work of one man alone. Linus Torvalds is the original architect of Linux, its father if you will, but he is not the only effort behind it. Perhaps Linus Torvalds' greatest genius lay in knowing when to share the load. For no other pay but satisfaction, he employed people around the world, delegated to them, worked with them, and asked for and accepted feedback in a next generation of the model that began with the GNU project.

GNU, by the way, is a recursive acronym that stands for "GNU's Not Unix," a project of the Free Software Foundation. This project was started in 1984 with the intention of creating a free, UNIX-like operating system. Over the years, many GNU tools were written and widely used by many commercial UNIX vendors and, of course, system administrators trying to get a job done. The appearance of Linus Torvalds' Linux kernel had made the GNU dream of a completely free, UNIX-like operating system a reality at last.

Why Linux?

Because this book is not so much about getting and installing Linux as it is working with Linux, I won't spend a long time answering the question "Why Linux?" Frankly, it would take much less time to answer the question "Why not Linux?" Suffice it to say that Linux is a powerful, reliable (some, including your humble author, might even say it's rock solid), expandable, flexible, configurable, multiuser, multitasking, and completely free operating system that runs on numerous hardware offerings. These hardware offerings include X86 chipsets (your basic, run-of-the-mill Intel PC), DEC Alpha, Macintosh, PowerPC, and a growing number of embedded processors. You can find Linux in PDA organizers, digital watches, golf carts, and cell phones. In fact, Linux has a greater support base (in terms of platforms) than just about any other operating system you can think of. IBM's entire line of hardware runs Linux!

Completely free?

Hmm . . . Maybe I should explain "free." Free, in this case, isn't a question of cost, although you can get a free/gratis copy of Linux and install it on your system without breaking any laws. Of course, because "there ain't no such thing as a free lunch" (to quote Robert A. Heinlein), even a free download costs you connection time on the Internet, disk space, time, and so on.

Linux is distributed under the GNU General Public License (GPL), which in essence says that anyone may copy, distribute, and even sell the program so long as changes to the source are reintroduced back to the community and the terms of the license remain unaltered. Free means that you are free to take Linux, modify it, and create your own version. Free means that you are not at the mercy of a single vendor who forces you into a kind of corporate servitude by making sure that it is extremely costly to convert to another environment. If you are unhappy with your Linux vendor or the support you are getting, you can move to the next vendor without forfeiting your investment in Linux.

The GNU GPL permits a distributor to "charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee." This is further qualified by the statement that the distributor must release "for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code." In other words, the GPL ensures that programs like Linux will at best be free of charge. At worst, you may be asked to pay for the cost of a copy.

Everyone should take some time to read the GNU GPL. You'll find a link to its home in the Resources section at the end of this chapter.

The System Administrator's Job

So, this book is about Linux system administration. Just what the heck is system administration anyway? System (or systems) administration is a strange beast. After many years of administering literally hundreds of computer platforms running different operating systems and varying in complexity, I came to have what some might call a strange idea of this job description.

system administrator n. Part magician, part juggler, part technical support analyst, and part bartender/psychoanalyst, the system administrator performs the impossible job of keeping all members of his or her company satisfied by making sure that everything works. This usually includes things that are completely outside the system administrator's control, such as telephones, photocopiers, fax machines, heating, air conditioning, and paper shortages in the supply cabinet.

I'm being a little silly, I realize, but system administrators get to their exulted position through the strangest of ways. You will find the career system administrator who actually wanted to do the job and worked his or her way to that goal. Along this path, you will also find secretaries who were unfortunate enough (or foolish enough) to say they knew something about computers and were instantly cast into the role. This latter category of sysadmin (a popular shortening of "system administrator") is more common than you can possibly imagine. Finally, you have the home user, a relative newcomer to this wonderful calling, thanks in large part to Linux.

About This Book

When I first started thinking about how I would lay out this book, I considered a number of approaches and settled on the following. I don't want to bore you, the reader, with chapters of references to HOWTOs on the Internet (although I will give you appropriate resource links when necessary). Nor do I want to give you verbatim listings of command options or man pages.

What I do want to do is give you real-life examples and things that you can try yourself to get the most out of your system. You will get the theory as well, but only so much. I want you to walk away with an understanding that only comes from actually doing things. The most fun I have ever had in the computer biz came from doing things, trying things out, and basically just playing. Computers can be fun, even when you are working instead of playing games. This is cool stuff. Imagine--a machine that does what you tell it to do! When the printer is jammed up and your connection to the Internet is down, you tend to forget how marvelous all this really is. So, saddle up to your keyboard, pour yourself a cup of java (that's coffee, not the programming language), limber up those fingers, and start playing.

An assumption I've decided to make is that you already have a Linux system to work with. What you want to know is how to work with it better. This doesn't mean I intend to skimp on anything. I will compare various installation philosophies and distributions so that you can satisfy your curiosity about other Linuxes. Which provides me with the perfect segue into another assumption I've decided to make.

Linux is an operating system kernel supported and bundled into an operating system distribution, which is then marketed, sold, or given away by many different companies or organizations. What this means is that I will try to cover the quirks related to various distributions that may affect you when you try out the things you read in this book. I can't promise that I'll cover every possible distribution here, but what I will do is give you the tools to discover where your version of a particular configuration file or script fits into your system so that you can at least find it. Suffice it to say that even in cases of "my file was here rather than there," the formats, at least, will tend to be constant.

0201719347P09242001