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Red Hat Enterprise Linux Troubleshooting Guide
Red Hat Enterprise Linux Troubleshooting Guide

Red Hat Enterprise Linux Troubleshooting Guide: Identify, capture and resolve common issues faced by Red Hat Enterprise Linux administrators using best practices and advanced troubleshooting techniques

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Red Hat Enterprise Linux Troubleshooting Guide

Chapter 2. Troubleshooting Commands and Sources of Useful Information

In the first chapter, we covered troubleshooting best practices and the high level process involved. Where the first chapter was a 20,000 ft view on troubleshooting, this chapter starts to dive into the specifics.

This chapter will review common troubleshooting commands as well as common places to find helpful information. Within this book, we will utilize release 7 of Red Hat Enterprise Linux (also referred to as RHEL). All commands referenced in this chapter will be commands that are included with a default installation of RHEL 7.

We will reference commands that are installed by default, as I have found myself in situations where I could have used a specific command to identify an issue immediately but that command was not available to me. By limiting this chapter to default commands, you can be assured that the troubleshooting steps covered in this chapter are not only relevant to most RHEL 7 installations...

Finding useful information

Before starting to explore troubleshooting commands, I first want to cover locations of useful information. Useful information is a bit of a vague term, pretty much every file, directory, or command can provide useful information. What I really plan to cover are places where it is possible to find information for almost any issue.

Log files

Log files are often the first place to start looking for troubleshooting information. Whenever a service or server is experiencing an issue, checking the log files for errors can often answer many questions quickly.

The default location

By default, RHEL and most Linux distributions keep their log files in /var/log/, which is actually part of the Filesystem Hierarchy Standard (FHS) maintained by the Linux Foundation. However, while /var/log/ might be the default location not all log files are located there (http://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard).

While /var/log/httpd/ is the default location for Apache logs...

Troubleshooting commands

This section will cover frequently used troubleshooting commands that can be used to gather information from the system or a running service. While it is not feasible to cover every possible command, the commands used do cover fundamental troubleshooting steps for Linux systems.

Command-line basics

The troubleshooting steps used within this book are primarily command-line based. While it is possible to perform many of these things from a graphical desktop environment, the more advanced items are command-line specific. As such, this book assumes that the reader has at least a basic understanding of Linux. To be more specific, this book assumes that the reader has logged into a server via SSH and is familiar with basic commands such as cd, cp, mv, rm, and ls.

For those who might not have much familiarity, I wanted to quickly cover some basic command-line usage that will be required knowledge for this book.

Command flags

Many readers are probably familiar with the following...

Summary

In this chapter, you learned that log files, configuration files, and the /proc filesystem are key sources of information during troubleshooting. We also covered the basic use of many fundamental troubleshooting commands.

While reading this chapter, you might have noticed that quite a few commands are also used in day-to-day life for non-troubleshooting purposes. If we look back at the troubleshooting process from Chapter 1, Troubleshooting Best Practices, the first step included information gathering.

While these commands might not explain the issue themselves, they can help gather information about the issue, which leads to a more accurate and quick resolution. Familiarity with these fundamental commands is critical to your success during troubleshooting.

In the next few chapters, we will use these fundamental commands to troubleshoot real-world scenarios. The next chapter focuses on troubleshooting issues with a web-based application.

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Key benefits

  • Develop a strong understanding of the base tools available within Red Hat Enterprise Linux (RHEL) and how to utilize these tools to troubleshoot and resolve real-world issues
  • Gain hidden tips and techniques to help you quickly detect the reason for poor network/storage performance
  • Troubleshoot your RHEL to isolate problems using this example-oriented guide full of real-world solutions

Description

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.

Who is this book for?

If you have a basic knowledge of Linux from administration or consultant experience and wish to add to your Red Hat Enterprise Linux troubleshooting skills, then this book is ideal for you. The ability to navigate and use basic Linux commands is expected.

What you will learn

  • Identify issues that need rapid resolution against long term root cause analysis
  • Discover commands for testing network connectivity such as telnet, netstat, ping, ip and curl
  • Spot performance issues with commands such as top, ps, free, iostat, and vmstat
  • Use tcpdump for traffic analysis
  • Repair a degraded file system and rebuild a software raid
  • Identify and troubleshoot hardware issues using dmesg
  • Troubleshoot custom applications with strace and knowledge of Linux resource limitations

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Oct 19, 2015
Length: 458 pages
Edition : 1st
Language : English
ISBN-13 : 9781785283550
Vendor :
Red Hat
Concepts :
Tools :

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Product Details

Publication date : Oct 19, 2015
Length: 458 pages
Edition : 1st
Language : English
ISBN-13 : 9781785283550
Vendor :
Red Hat
Concepts :
Tools :

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Table of Contents

13 Chapters
1. Troubleshooting Best Practices Chevron down icon Chevron up icon
2. Troubleshooting Commands and Sources of Useful Information Chevron down icon Chevron up icon
3. Troubleshooting a Web Application Chevron down icon Chevron up icon
4. Troubleshooting Performance Issues Chevron down icon Chevron up icon
5. Network Troubleshooting Chevron down icon Chevron up icon
6. Diagnosing and Correcting Firewall Issues Chevron down icon Chevron up icon
7. Filesystem Errors and Recovery Chevron down icon Chevron up icon
8. Hardware Troubleshooting Chevron down icon Chevron up icon
9. Using System Tools to Troubleshoot Applications Chevron down icon Chevron up icon
10. Understanding Linux User and Kernel Limits Chevron down icon Chevron up icon
11. Recovering from Common Failures Chevron down icon Chevron up icon
12. Root Cause Analysis of an Unexpected Reboot Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

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Full star icon Full star icon Full star icon Full star icon Half star icon 4.7
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Amazon Customer Jun 19, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Good
Amazon Verified review Amazon
Gjorgi Var Aug 30, 2016
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This guide is awesome, it is precise when needed and also gives perspective with general explanation when needed . Obviously author draws from his own experience but principles and solutions are applicable to any red hat linux setting.Absolutely recommended for those working with linux on daily basis as well as for the aspiring admin. I'm also using this book as a resource to prepare for Red Hat's CoE Diagnosing and Troubleshooting RHEL 7.
Amazon Verified review Amazon
Abital Dec 22, 2016
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The author guides us step by step (and precisely) to explore most of the possible ways to analyze a given problem. And this is why it's not a book as the others...This book is a part of few books that we buy blindness, to say to himself then that we have for his money, and very widely...Then, we would like that the author writes a book every day! I really greet this author...I'm looking for a similar book on Linux/Network security...
Amazon Verified review Amazon
Perry Nally Dec 31, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Red Hat Enterprise Linux Troubleshooting Guide may just be all you need in your quest to wear the red hat. May I remind you that this is not a "getting started guide", but a troubleshooting guide. This assumes you are somewhat familiar with Red Hat Linux and you may be having difficulty with a particular scenario. If that's your situation, then this book IS your book.The information is organized well with respect to topics and real world scenarios and the appropriate solutions. I found that most of the principles described behind the scenarios could be generally used to troubleshoot other Linux environments as well; which makes this book even more valuable.I think a book like this should be written for every OS that exists.
Amazon Verified review Amazon
SuJo Dec 25, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Working with Red Hat daily so this book was a no brainier of a purchase, since Packt has a global $5.00 sale right now on all of their books. The book has a nice flow, and all of the information was well received. I enjoyed the section on tcpdump, and the coverage on /dev was on point. I highly recommend this book not only for Red Hat, but it's pertinent to Centos and you can even tweak it enough to get away with doing some diagnostic work on Debian based Linux distributions.
Amazon Verified review Amazon
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