Book Image

Red Hat Enterprise Linux Troubleshooting Guide

By : Benjamin Cane
Book Image

Red Hat Enterprise Linux Troubleshooting Guide

By: Benjamin Cane

Overview of this book

Red Hat Enterprise Linux is an operating system that allows you to modernize your infrastructure, boost efficiency through virtualization, and finally prepare your data center for an open, hybrid cloud IT architecture. It provides the stability to take on today's challenges and the flexibility to adapt to tomorrow's demands. In this book, you begin with simple troubleshooting best practices and get an overview of the Linux commands used for troubleshooting. The book will cover the troubleshooting methods for web applications and services such as Apache and MySQL. Then, you will learn to identify system performance bottlenecks and troubleshoot network issues; all while learning about vital troubleshooting steps such as understanding the problem statement, establishing a hypothesis, and understanding trial, error, and documentation. Next, the book will show you how to capture and analyze network traffic, use advanced system troubleshooting tools such as strace, tcpdump & dmesg, and discover common issues with system defaults. Finally, the book will take you through a detailed root cause analysis of an unexpected reboot where you will learn to recover a downed system.
Table of Contents (19 chapters)
Red Hat Enterprise Linux Troubleshooting Guide
About the Author
About the Reviewers


Red Hat Enterprise Linux is a widely popular Linux distribution that is used in everything from Cloud to enterprise mainframe computers. If you include downstream distributions such as CentOS, the adoption of the Red Hat Enterprise Linux distribution is even greater.

As with most things, there is always someone responsible for resolving issues with all of these various systems running Red Hat Enterprise Linux. Red Hat Enterprise Linux Troubleshooting Guide is written to provide basic to advanced troubleshooting practices and commands for Linux systems, with these troubleshooting techniques specifically focused on systems running Red Hat Enterprise Linux.

This book is designed to provide you with steps and the knowledge required to remedy a wide variety of scenarios. The examples in this book use real-world issues with real-world resolutions.

While the examples in this book are situational, this book can also be used as a reference for Linux-related topics and commands. They provide the reader with the ability to reference both troubleshooting steps and specific commands to resolve complex issues.

What this book covers

Chapter 1, Troubleshooting Best Practices, covers the troubleshooting process at a high level. By equating the troubleshooting process with the scientific method, this book will explain how to break down a problem to identify the root cause, no matter how complicated the problem.

Chapter 2, Troubleshooting Commands and Sources of Useful Information, provides the reader with a simple introduction to common locations of useful information. It will also provide a reference for fundamental Linux commands that can be used for troubleshooting many types of issues.

Chapter 3, Troubleshooting a Web Application, takes the process learned in Chapter 1 and the commands learned in Chapter 2 to work through a complicated problem. The problem outlined in this chapter is "By example" meaning that the flow of this chapter is designed to walk you through the entire troubleshooting process, from end to end.

Chapter 4, Troubleshooting Performance Issues, deals with performance issues and some of the most complicated problems to troubleshoot. Often, the complications are compounded by the perception of users versus expected levels of performance. In this chapter, the tools and information discussed in Chapter 2 will, once again, be used to resolve a real-world performance problem.

Chapter 5, Network Troubleshooting, talks about networking being a critical component of any modern day system. This chapter will cover the core commands necessary for the configuration and diagnostics of Linux networking.

Chapter 6, Diagnosing and Correcting Firewall Issues, covers the complex nature of Linux firewalls, in a continuation of Chapter 5. This chapter will introduce and highlight commands and techniques necessary to troubleshoot Linux software firewalls.

Chapter 7, Filesystem Errors and Recovery, teaches you that being able to recover a filesystem could mean the difference between losing and retaining data. This chapter will introduce some core Linux filesystem concepts and will demonstrate how to recover a read-only filesystem.

Chapter 8, Hardware Troubleshooting, starts to touch on the process of troubleshooting hardware issues. This chapter will walk you through the restoration of a failed hard drive.

Chapter 9, Using System Tools to Troubleshoot Applications, explores how often a system administrator's role is not only to troubleshoot OS issues but also application issues. This chapter will show you how to utilize common system tools to identify the root cause of an application issue.

Chapter 10, Understanding Linux User and Kernel Limits, demonstrates that Red Hat Enterprise Linux has many components in place to prevent users from overloading the system. This chapter will explore these components and explain how to modify them to allow legitimate resource utilization.

Chapter 11, Recovering from Common Failures, walks you through troubleshooting out-of-memory conditions. This scenario is very common in heavily utilized environments and can be difficult to troubleshoot. This chapter will cover not only how to troubleshoot this issue, but also why the issue occurred.

Chapter 12, Root Cause Analysis of an Unexpected Reboot, puts the troubleshooting process and commands learned in the previous chapters to the test. This chapter walks you through performing a Root Cause Analysis on a server that has unexpectedly rebooted.

What you need for this book

Although this book can be standalone, readers will benefit greatly from having a system with Red Hat Enterprise Linux release 7, with the operating system available. You will more effectively learn the commands and resources discussed in this book when you have the ability to execute them on a test system.

While it is possible to use many of the commands, processes, and resources covered in this book with other Linux distributions, it is highly recommended to utilize a Red Hat downstream distribution such as CentOS 7 if Red Hat Enterprise Linux 7 is not available to the reader.

Who this book is for

If you are a competent RHEL administrator or consultant with a desire to increase your troubleshooting skills and your knowledge of Red Hat Enterprise Linux, then this book is perfect for you. A good knowledge level and understanding of basic Linux commands are expected.


In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "Within reason, it is not required to include every cd or ls command executed."

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold: > ICMP host unreachable - admin prohibited, length 68

Any command-line input or output is written as follows:

# yum install man-pages

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "we will see a message on our screen that says still here?."


Warnings or important notes appear in a box like this.


Tips and tricks appear like this.

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