Understanding the Linux® Virtual Memory Manager

By Mel Gorman

Linux is developed with a stronger practical emphasis than a theoretical one. When new algorithms or changes to existing implementations are suggested, it is common to request code to match the argument. Many of the algorithms used in the Virtual Memory (VM) system were designed by theorists, but the implementations have now diverged considerably from the theory. In part, Linux does follow the traditional development cycle of design to implementation, but changes made in reaction to how the system behaved in the “real world” and intuitive decisions by developers are more common.

This means that the VM performs well in practice. However, very little VM documentation is available except for a few incomplete overviews on a small number of Web sites, except the Web site containing an earlier draft of this book, of course! This lack of documentation has led to the situation where the VM is fully understood only by a small number of core developers. New developers looking for information on how VM functions are generally told to read the source. Little or no information is available on the theoretical basis for the implementation. This requires that even a casual observer invest a large amount of time reading the code and studying the field of Memory Management.

This book gives a detailed tour of the Linux VM as implemented in 2.4.22 and gives a solid introduction of what to expect in 2.6. As well as discussing the implementation, the theory that Linux VM is based on will also be introduced. This is not intended to be a memory management theory book, but understanding why the VM is implemented in a particular fashion is often much simpler if the underlying basis is known in advance.

To complement the description, the appendices include a detailed code commentary on a significant percentage of the VM. This should drastically reduce the amount of time a developer or researcher needs to invest in understanding what is happening inside the Linux VM because VM implementations tend to follow similar code patterns even between major versions. This means that, with a solid understanding of the 2.4 VM, the later 2.5 development VMs and the 2.6 final release will be decipherable in a number of weeks.

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Linux Network Administrator's Guide, 2nd Edition

By Olaf Kirch & Terry Dawson

This book was written to provide a single reference for network administration in a Linux environment. Beginners and experienced users alike should find the information they need to cover nearly all important administration activities required to manage a Linux network configuration. The possible range of topics to cover is nearly limitless, so of course it has been impossible to include everything there is to say on all subjects. We've tried to cover the most important and common ones. We've found that beginners to Linux networking, even those with no prior exposure to Unix-like operating systems, have found this book good enough to help them successfully get their Linux network configurations up and running and get them ready to learn more.

There are many books and other sources of information from which you can learn any of the topics covered in this book (with the possible exception of some of the truly Linux-specific features, such as the new Linux firewall interface, which is not well documented elsewhere) in greater depth. We've provided a bibliography for you to use when you are ready to explore more.

Overview
Chapter 1, Introduction to Networking, discusses the history of Linux and covers basic networking information on UUCP, TCP/IP, various protocols, hardware, and security. The next few chapters deal with configuring Linux for TCP/IP networking and running some major applications. We examine IP a little more closely in Chapter 2, Issues of TCP/IP Networking, before getting our hands dirty with file editing and the like. If you already know how IP routing works and how address resolution is performed, you can skip this chapter.

Chapter 3, Configuring the Networking Hardware, deals with very basic configuration issues, such as building a kernel and setting up your Ethernet card. The configuration of your serial ports is covered separately in Chapter 4, Configuring the Serial Hardware, because the discussion does not apply to TCP/IP networking only, but is also relevant for UUCP.

Chapter 5, Configuring TCP/IP Networking, helps you set up your machine for TCP/IP networking. It contains installation hints for standalone hosts with loopback enabled only, and hosts connected to an Ethernet. It also introduces you to a few useful tools you can use to test and debug your setup.

Chapter 6, Name Service and Resolver Configuration, discusses how to configure hostname resolution and explains how to set up a name server.

Chapter 7, Serial Line IP, explains how to establish SLIP connections and gives a detailed reference for dip, a tool that allows you to automate most of the necessary steps.

Chapter 8, The Point-to-Point Protocol, covers PPP and pppd, the PPP daemon.

Chapter 9, TCP/IP Firewall, extends our discussion on network security and describes the Linux TCP/IP firewall and its configuration tools: ipfwadm, ipchains, and iptables. IP firewalling provides a means of controlling who can access your network and hosts very precisely.

Chapter 10, IP Accounting, explains how to configure IP Accounting in Linux so you can keep track of how much traffic is going where and who is generating it.

Chapter 11, IP Masquerade and Network Address Translation, covers a feature of the Linux networking software called IP masquerade, which allows whole IP networks to connect to and use the Internet through a single IP address, hiding internal systems from outsiders in the process.

Chapter 12, Important Network Features, gives a short introduction to setting up some of the most important network applications, such as rlogin, ssh, etc. This chapter also covers how services are managed by the inetd superuser, and how you may restrict certain security-relevant services to a set of trusted hosts.

Chapter 13, The Network Information System, and Chapter 14, The Network File System, discuss NIS and NFS. NIS is a tool used to distribute administative information, such as user passwords in a local area network. NFS allows you to share filesystems between several hosts in your network.

In Chapter 15, IPX and the NCP Filesystem, we discuss the IPX protocol and the NCP filesystem. These allow Linux to be integrated into a Novell NetWare environment, sharing files and printers with non-Linux machines.

Chapter 16, Managing Taylor UUCP, gives you an extensive introduction to the administration of Taylor UUCP, a free implementation of the UUCP suite.
The remainder of the book is taken up by a detailed tour of electronic mail and Usenet news.

Chapter 17, Electronic Mail, introduces you to the central concepts of electronic mail, like what a mail address looks like, and how the mail handling system manages to get your message to the recipient.

Chapter 18, Sendmail, and Chapter 19, Getting Exim Up and Running, cover the configuration of sendmail and exim, two mail transport agents you can use for Linux. This book explains both of them, because exim is easier to install for the beginner, while sendmail provides support for UUCP.

Chapter 20, Netnews, through Chapter 23, Internet News, explain the way news is managed in Usenet and how you install and use C News, nntpd, and INN: three popular software packages for managing Usenet news. After the brief introduction in Chapter 20, you can read Chapter 21, C News, if you want to transfer news using C News, a traditional service generally used with UUCP. The following chapters discuss more modern alternatives to C News that use the Internet-based protocol NNTP (Network News Transfer Protocol). Chapter 22, NNTP and the nntpd Daemon covers how to set up a simple NNTP daemon, nntpd, to provide news reading access for a local network, while Chapter 23 describes a more robust server for more extensive NetNews transfers, the InterNet News daemon (INN). And finally, Chapter 24, Newsreader Configuration, shows you how to configure and maintain various newsreaders.

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Linux System Administrator's Survival Guide

By Tim Parker

UNIX system administration used to be a skill learned by watching others, trying many things on spec, and scouring obscure magazine articles, obtuse man pages, and e-mail from others. In short, system administration was a skill that was learned over the years with no single reference to the role and functions a system administrator plays. UNIX, especially, was a tough system to administer properly because there were many versions of the software, a disparate support base, and few solid working applications. Luckily, time has changed these conditions.

With the popularity of computers in general, system administrators started writing down the details of their tasks. Publishers realized that there was a distinct and eager, albeit small, market for system administration books. The market grew as the number of systems and LANs expanded. The stabilization of the UNIX operating system in two, and now one, major version helped enormously as well.

Linux became a dominant UNIX product about two years ago when it started receiving worldwide acclaim as a reasonably stable PC version of UNIX. As more and more programmers got involved and started producing software for Linux, the attraction of the operating system continued to grow. Soon, PC users who didn't know anything about UNIX at all were running Linux and starting to deal with shells, filesystems, and devices.

After helping to write Linux Unleashed (a great book, definitely worth buying if you haven't already got a copy!), I realized that many users used that book and CD-ROM to get started with Linux, but they needed more advanced material on managing their systems and setting up network systems. That's when the Linux System Administrator's Survival Guide was born. This book expands on the Linux Unleashed material, providing more detail on many aspects of the operating system. Although some overlap exists between Linux Unleashed and this book, it has been minimized as much as possible. Relative newcomers to Linux will still find that that book is very readable, however.

Many Linux books are available, but to date there are no complete books on administering a Linux system. A few books do cover specific aspects of the task, such as networking or device drivers, but none cover the entire gamut. That's the task I set for myself when this book was born: give readers enough information to help them get their Linux systems running smoothly. The next problem was how to condense 20 years of UNIX system administration experience into a single book. It took a while, but I hope I've managed to include enough information on every aspect of system administration to keep you going.

Bear in mind that this book was written for the system administrator, although the material will certainly be applicable (and hopefully interesting) to any user who has mastered the basics of Linux. I cover practically every aspect of system administration in this book. When dealing with subjects, like security, that have entire books written on them, I cover only the basics. Also, I don't include all the details about the more obscure topics that aren't relevant to most readers.
This book should provide you with everything you need, from setting up filesystems to installing servers for popular Internet utilities. The book was not written for the advanced user; it was written for those just starting in system administration. I hope you find a lot of useful information in this book.

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