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
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

A quick summary of what you have learned so far


From our troubleshooting so far, we have identified that the blog server is able to establish a connection to the database server over port 22. This connection is actually able to perform a full three-way handshake unlike our previous chapter. However, the blog server is not able to perform a three-way handshake with the database server over port 3306, the database port.

When the blog server attempts to establish a connection to the database server over port 3306, the database server is sending an ICMP destination unreachable packet back to the blog server. This packet is essentially telling the blog server that the connection attempt to the database is being rejected. Yet, the database service is up and listening on port 3306 (verified with netstat). In addition to the port being listened to, if we telnet to port 3306 locally, from the database server itself the connection is established.

Given all of these data points, it is possible that the...