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

Diagnosing filesystem errors


Unlike earlier chapters where end users were reporting the issue to us, this time around we have found an issue for ourselves. While performing some daily tasks on the database server we attempted to create a database backup and received the following error:

[db]# mysqldump wordpress > /data/backups/wordpress.sql
-bash: /data/backups/wordpress.sql: Read-only file system

This error is interesting because it is not necessarily from the mysqldump command, but rather from the bash redirect that writes to the /data/backups/wordpress.sql file.

If we look at the error it is very specific, the filesystem we were attempting to write the backup to, is Read-only. What does Read-only mean?

Read-only filesystems

When defining and mounting filesystems on Linux you have many options, but there are two options that define the filesystem's accessibility best. Those two options are rw for read and write, and ro for read-only. When a filesystem is mounted with the read and write...