The Official Ubuntu Book Third Edition Benjamin Mako Hill with Corey Burger, Jonathan Jesse, and Jono Bacon Upper Saddle River, NJ • Boston • Indianapolis • San Francisco New York • Toronto • Montreal • London • Munich • Paris • Madrid Capetown • Sydney • Tokyo • Singapore • Mexico City Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals. The authors and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein. 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To gain 45-day Safari Enabled access to this book: • Go to www.informit.com/onlineedition • Complete the brief registration form • Enter the coupon code X1HW-8MDI-4MVQ-BRID-V41D If you have difficulty registering on Safari Bookshelf or accessing the online edition, please e-mail [email protected]. Visit us on the Web: www.informit.com/ph Library of Congress Cataloging-in-Publication Data The official Ubuntu book / Benjamin Mako Hill ... [et al.].— 3rd ed. p. cm. Includes index. ISBN 0-13-713668-4 (pbk. : alk. paper) 1. Ubuntu (Electronic resource) 2. Operating systems (Computers) I. Hill, Benjamin Mako, 1980– QA76.76.O63O34348 2008 005.4'3—dc22 2008020805 Copyright © 2008 Canonical, Ltd. This book is published under the Creative Commons Attribution-ShareAlike 3.0 license, http://creativecommons.org/licenses/ by-sa/3.0/. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise unless permitted under the Creative Commons Attribution-ShareAlike license 3.0. For information regarding permissions, write to: Pearson Education, Inc., Rights and Contracts Department, 501 Boylston Street, Suite 900, Boston, MA 02116, Fax: (617) 671-3447. ISBN 13: 978-0-13-713668-1 ISBN 10: 0-13-713668-4 Text printed in the United States on recycled paper at Courier in Stoughton, Massachusetts. First printing, June 2008 CHAPTER 5 The Ubuntu Server What Is Ubuntu Server? Installing Ubuntu Server 5 Ubuntu Package Management Ubuntu Server Security Summary Copyright 2008 Canonical, Ltd. 147 UBUNTU 4.10, LOVINGLY KNOWN AS WARTY WARTHOG, was the first public ver- sion of Ubuntu. Its installation media provided no obvious way to install the bare-bones OS without a full desktop environment. The system administrator crowds, easily irritable and feisty by nature, were greatly annoyed: They proclaimed Ubuntu was just a desktop distribution and sauntered back to their caves in contempt. The next release of Ubuntu that came out, Hoary Hedgehog, rectified the problem and allowed for trivial installation of a minimal Ubuntu version suitable for servers. Yet the myth of Ubuntu as a purely desktop-oriented distribution stuck. Luckily, the sentiment is just that—a myth. Ubuntu is a world-class server platform today, providing everything you’d expect from a server OS and with the human flavor that makes Ubuntu different. The dedicated hack- ers on the Ubuntu Server Team that tends to the minutiae of hardware support and testing mercilessly beat on the latest version of server software to make sure it’s up to snuff for inclusion in the distribution, and the members of the team are available to users like you to field feedback, ques- tions, and cries of anguish. That said, setting up a server is no small task. Server administrators con- stantly deal with complex issues such as system security, fault tolerance, and data safety, and while Ubuntu makes these issues more pleasant to deal with, they’re not to be taken lightly. The aim of this chapter is thus not to teach you how to be a system administrator—we could easily fill a dozen books attempting to do that—but to give you a quick crash course. We’ll also high- light the specific details that set Ubuntu Server apart from other server plat- forms, offer tips on some of the most common server uses, and give you pointers on where to find other relevant information. Let the mischief begin! What Is Ubuntu Server? By far the most common reaction from users first encountering Ubuntu Server is one of utter and hopeless confusion. People are foggy on whether 148 Copyright 2008 Canonical, Ltd. What Is Ubuntu Server? 149 Ubuntu Server is a whole new distribution or an Ubuntu derivative like Kubuntu (only for servers) or perhaps something else entirely. Let’s clear things up a bit. The primary software store for Ubuntu and offi- cial derivatives is called the Ubuntu archive. The archive is merely a collec- tion of software packages in Debian “deb” format, and it contains every single package that makes up distributions such as Ubuntu, Edubuntu, Xubuntu, Kubuntu, and Ubuntu Server. What makes Kubuntu separate from Ubuntu, then, is only the set of packages from the archive that its installer installs by default and that its CDs carry. Ubuntu Server is no different. It depends on the very same archive as the standard Ubuntu distribution, but it installs a distinctive set of default packages. Notably, the set of packages comprising Ubuntu Server is very small. The installer will not install things such as a graphical environment or many user programs by default. But since all the packages for Ubuntu Server come from the same official Ubuntu archive, you can install any package you like later. In theory, there’s nothing stopping you from trans- forming an Ubuntu Server install into a regular Ubuntu desktop installa- tion or vice versa (in practice, this is tricky, and we don’t recommend you try it). You can even go from running Kubuntu to running Ubuntu Server. The archive paradigm gives you maximum flexibility. We’ve established that Ubuntu Server just provides a different set of default packages than Ubuntu. But what’s important about that different set? What makes Ubuntu Server a server platform? The most significant difference is a nonpreemptible server kernel with an internal kernel timer frequency of 100Hz instead of the desktop default of 1KHz. We’ll spare you the OS theory: The idea is to offer some extra per- formance and throughput for server applications. In addition, the server kernel supports SMP and basic NUMA. SMP, or symmetric multiprocess- ing, is the code that allows you to use more than one processor in your server, and NUMA is a memory design used in some multiprocessor sys- tems that can dramatically increase multiprocessing performance. Copyright 2008 Canonical, Ltd. 150 Chapter 5 The Ubuntu Server So what else is different in Ubuntu Server? Other than the server kernel and a minimal set of packages, not too much. Though Ubuntu has supported a minimal installation mode for a number of releases, spinning off Ubuntu Server into a proper derivative distribution is still a young effort, and many neat features are planned for the future but aren’t available just yet. Starting with Ubuntu Server 6.06 LTS, known as Dapper Drake, Ubuntu Server offers officially supported packages for the Red Hat Cluster Suite, Red Hat’s Global File System (GFS), Oracle’s OCFS2 filesystem, and the Linux Virtual Server utilities: keepalived and ipvsadm. Combined with the specialized server kernel, these bits already let you use your Ubuntu Server for some heavy lifting. And there’s a great lineup of upcoming fea- tures: Among other things, we’re hoping to throw in a resource manager for cluster folks, automatically place system configuration files under version control, ship with out-of-the-box support for server farm moni- toring and hard drive replication over the network, and provide an integrity checker for installed systems directly on Ubuntu CDs. Installing Ubuntu Server So you’ve downloaded your Ubuntu Server CD from http://releases. ubuntu.com/8.04/ and burned it, eagerly placed it in your CD drive, and rebooted the machine to be greeted by the friendly Ubuntu menu. The first option, Install Ubuntu Server, marks the beginning of a journey toward your very own system administrator cave. For the most part, server installation is identical to installing a regular Ubuntu machine. This is because Ubuntu takes extra care to ask only the most fundamental questions in the installer, and it turns out those don’t differ much between a desktop and a server system. For a quick review of the installation procedure, turn back to Chapter 2. Here, we’ll be looking at some of the advanced installer gadgetry that the earlier chapter leaves out and that is particularly geared toward server users.