Table of Contents

Preface

Chapter 1. System Boot, Startup, and Shutdown Issues

Bootloaders

GRUB

Editing the Menu Choices with GRUB

LILO

Booting When GRUB or LILO Doesn’t Work

The init Process and/etc/inittab File

Startup in Multiuser Mode

init errors

rc Scripts

Confirm Mode

Startup Problems in rc Scripts

Fixing Problems with the Root Filesystem

Booting from a Second Hard Disk

Booting from a Rescue CD

Reset Lost Root Password Using a Knoppix CD

Reinstall GRUB Using Knoppix CD

Booting from a Floppy Rescue Disk

Summary

Endnotes

Chapter 2. System Hangs and Panics

OS Hangs

Troubleshooting Interruptible Hangs

Troubleshooting Non-Interruptible Hangs

OS Panics

Troubleshooting OS Panics

Troubleshooting Panics Resulting from Oops

Hardware Machine Checks

Summary

Chapter 3. Performance Tools

top

Adding and Removing Fields

Output Explained

Saving Customization

Batch Mode

sar

sar Data Collector

CPU Statistics

Disk I/O Statistics

Networking Statistics

vmstat

iostat

free

Summary

Endnotes

Chapter 4. Performance

Start Troubleshooting at the Lowest Layer Possible

Binding a Raw Device to a Block Device Using the raw Command

Raw Device Performance

Using the dd Command to Determine Sequential I/O Speed

Using sar and iostat to Measure Disk Performance

Understanding the Importance of I/O Block Size When Testing Performance

Multiple Threads (Processes) of I/O to a Disk

Using a Striped lvol to Reduce Disk I/O Strain

Multipath I/O

Filesystems

Journaling to a Separate Disk

Determining I/O Size for Filesystem Requests

Loading a Filesystem with Small Block I/O Transfers

Utilizing Key Benefits of a Filesystem

Linux and Windows Performance and Tuning Sector Alignments

Performance Tuning and Benchmarking Using bonnie++

Assessing Application CPU Utilization Issues

Using Oracle statspak

Troubleshooting “No Space Left on Device” Errors When Allocating Shared Memory

Additional Performance Tools

isag

Summary

Chapter 5. Adding New Storage via SAN with Reference to PCMCIA and USB

Configuration

Kernel Module

Adding LUNs via PCI

Adding Storage via PCMCIA/USB

Summary

Chapter 6. Disk Partitions and Filesystems

Background

IDE and SCSI

Bit Calculation

Partition Table/Master Boot Record: Location

Partition Table/Master Boot Record: CHS Addressing

Defining a Primary Partition

Determining Whether Additional Partitions Can Be Created

Partition Table/Master Boot Record: Logical/Extended

Partition Table/Master Boot Record: Logical Block Addressing (LBA)

Partition Table/Master Boot Record: Bootloader

Byte Review on a Used Drive

BIOS Initializing the Bootloader

Partition Table/Master Boot Record: Backup

Partition Recovery Walkthrough

Demonstrating a Failure

Mounting a Partition

Recovering Superblock and Inode Table on ext Filesystems

Further Scenarios

Summary

Chapter 7. Device Failure and Replacement

Supported Devices

Where to Look for Errors

Identifying Failed Devices

Replacement of a Failed Device

Summary

Chapter 8. Linux Processes: Structure, Hangs, and Core Dumps

Process Structure and Life Cycle

Process/Task Overview

Process Relationships

Linux Process Creation

Linux Process Termination

Linux Threads

Identifying Threads

Identifying Process Hangs

Process Cores

Signals

Limits

The Core File

Summary

Chapter 9. Backup/Recovery

Media

Magnetic Tape

Optical Disk

Hard Disk

Backup Scope

Basic Backup and Recovery Commands

tar

cpio

dump and Restore

dd

mkisofs

rsync

Bare Metal Recovery

I Have a Tape, and I Don’t Know What It Is . . .

How Can I Tell Whether My Tape Problem Is Hardware or Software?

Summary

Chapter 10. cron and at

cron

cron Daemon

kcron

anacron

at

at Daemon and atrun

Troubleshooting cron

Methodology

Summary

Chapter 11. Printing and Printers

What Is a Spooler?

Using the Spooler Commands

Spooler Plumbing

Term Definitions

Printer Types

Connectivity Types

Local Serial Printing

Local USB Printing

Local Parallel Printing

Remote Printing

Raw Network Socket Printing

IPP

Terminal Servers (Networked Serial)

Page Description Languages

General Printing Troubleshooting

Mapping the Spooling Environment

Breakpoints

Summary

Chapter 12. System Security

What Is System Security?

Host Versus Network Security

What Is Vulnerability?

Classes of Host Vulnerabilities

Types of Vulnerabilities and Exposures

General Steps to Increase Host Security

Prevention

Encryption with SSH

System Hardening with netfilter/iptables

Patching

Recovery After Being Hacked

Summary

Chapter 13. Network Problems

An Introduction to the OSI and TCP/IP Layers

Troubleshooting the Network Layers

Troubleshooting the TCP/IP Physical Network Access Layer

Troubleshooting the Network Layer (OSI Third Layer, TCP/IP Second Layer)

Troubleshooting at the Transport Layer (TCP and UDP)

Troubleshooting at the Application Level: The Final Layer of the TCP/IP Model

Summary

Chapter 14. Login Problems

/etc/passwd, /etc/shadow, and Password Aging

/etc/passwd and /etc/shadow

chage, passwd, and usermod

/etc/passwd and /etc/shadow Corruption

pwck

Login Failures Due to Linux Configuration

/etc/securetty

/etc/nologin

PAM

Function

Priority

Module Name

Arguments

/etc/pam.d

/etc/pam.conf

/lib/security

Linux-PAM Resources

Troubleshooting PAM

Validate Modules

Bugs in PAM

Shell Problems

User Profile Files

Password Problems

Summary

Endnote

Chapter 15. X Windows Problems

X Background

X Components

X Server Component

X Client Component

X Display Manager

X Desktop Manager (Environment)

X Troubleshooting Scenarios

Summary

Endnotes

Index

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