Provides system administrators and end users with the tools and techniques to effectively troubleshoot Linux system problems.

James Kirkland is a Senior Consultant for Racemi David Carmichael works for Hewlett-Packard as a Technical Problem Manager in Alpharetta, Georgia Chris Tinker is a Senior Software Business Recovery Specialist for HP Greg Tinker's primary role is as a Storage Business Recovery Specialist

Preface Preface My good friend, James Kirkland, sent me an instant message one day asking if I wanted to write a Linux troubleshooting book with him. James has been heavily involved in Linux at the HP Response Center for several years. While troubleshooting Linux issues for customers, he realized there was not a good troubleshooting reference available. I remember a meeting discussing Linux troubleshooting. Someone asked what the most valuable Linux troubleshooting tool was. The answer was immediate. Google. If you have ever spent time trying to find a solution for a Linux problem, you know what that engineer was talking about. A wealth of great Linux information can be found on the Internet, but you can't always rely on this strategy. Some of the Linux information is outdated. A lot of it can't be understood without a good foundation of subject knowledge, and some of it is incorrect. We wanted to write this book so the Linux administrator will know how Linux works and how to approach and resolve common issues. This book contains the information we wish we had when we started troubleshooting Linux. Greg and Chris are identical twins and serious Linux hobbyists. They have been Linux advocates within HP for years. Yes, they both run Linux on their laptops. Chris is a member of the Superdome Server team ( http://www.hp.com/products1/servers/scalableservers/superdome/index.html ). Greg works for the XP storage team ( http://h18006.www1.hp.com/storage/xparrays.html ). Their Linux knowledge is wide and deep. They have worked through SAN storage issues and troubleshot process hangs, Linux crashes, performance issues, and everything else for our customers, and they have put their experience into the book. I am a member of the HP escalations team. I've primarily spent my time resolving HPUX issues. I've been a Linux hobbyist for a few years, and I've started working Linux escalations, but I'm definitely newer to Linux than the rest of the team. I try to give the book the perspective of someone who is fairly new to Linux. I tried to remember the questions I had when I first started troubleshooting Linux issues and included them in the book. We sincerely hope our effort is helpful to you. --Dave Carmichael Chapter Summaries These chapter summaries will give you an idea of how the book is organized and a bit of an overview of the content of each chapter. Chapter 1: System Boot, Startup, and Shutdown Issues Chapter 1 discusses the different subsystems that comprise Linux startup. These include the bootloaders GRUB and LILO, the init process, and the rc startup and shutdown scripts. We explain how GRUB and LILO work along with the important features of each. The reader will learn how to boot when there are problems with the bootloader. There are numerous examples. We explain how init works and what part it plays in starting Linux. The rc scripts are explained in detail as well. The reader will learn how to boot to single user mode, emergency mode, and confirm mode. Examples are included of using a recovery CD when Linux won't boot from disk. Chapter 2: System Hangs and Panics This chapter explains interruptible and non-interruptible OS hangs, kernel panics, and IA64 hardware machine checks. A Linux hang takes one of two forms. An interruptible hang is when Linux seems frozen but does respond to some events, such as a ping request. Non-interruptible hangs do not respond to any actions. We show how to use the Magic SysReq keystroke to generate a stack trace to troubleshoot an interruptible hang. We explain how to force a panic when Linux is in a non-