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Troubleshooting CentOS
Jonathan Hobson
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eBook - ePub
Troubleshooting CentOS
Jonathan Hobson
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Information
Troubleshooting CentOS
Table of Contents
Troubleshooting CentOS
Credits
About the Author
About the Reviewers
www.PacktPub.com
Support files, eBooks, discount offers, and more
Why subscribe?
Free access for Packt account holders
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Errata
Piracy
Questions
1. Basics of Troubleshooting CentOS
Installing some basic tools
Gathering hardware information
Understanding dmesg
Understanding log files
Reading log files and affecting the output
Using tail to monitor log files
Using cat, less, and more
Using grep
Using diff
Using truncation
Summary
References
2. Troubleshooting Active Processes
Tuning server performance with memory management and swap
Managing memory with vmstat
Checking the system load with the top command
Monitoring disk I/O with iotop
Checking processes with the ps command
Checking performance with iostat and lsof
Calculating the system load
Discovering process IDs with pgrep and systemctl
More about systemd
Issuing the kill signal
Dealing with an orphaned process
Summary
References
3. Troubleshooting the Network Environment
Using ping, dig, host, traceroute, and mtr
The ping command
The dig and host commands
The traceroute command
The mtr command
Monitoring network connections with the ss command
Packet analysis with tcpdump
Summary
References
4. Troubleshooting Package Management and System Upgrades
Gathering software information
Using Yum plugins
Fixing Yum operations
Installing additional Yum repositories
EPEL
Remi
The IUS repository
Downloading an RPM package with Yum
Diagnosing a corrupt RPM database
Minor release upgrades
Summary
References
5. Troubleshooting Users, Directories, and Files
Users
Adding users and forcing a password change
Deleting users
Modifying a user
Meet login.defs
Monitoring user activity with utmpdump
Resetting the root password and enhancing logging
Recovering lost or deleted files with Scalpel
Restoring file and directory permissions
Working with and extending the XFS filesystem
Running repairs on XFS
Investigating fragmentation on XFS
Auditing directories and files
Visualizing directories and files
Summary
References
6. Troubleshooting Shared Resources
Providing NFS shares on a CentOS 7 server
About NFS exports
Mounting NFS shares on a CentOS client
Mounting an external drive with CIFS
Using autofs to mount an external drive
Summary
References
7. Troubleshooting Security Issues
Auditing SELinux with aureport and setroubleshoot
SSH banners
Tuning SSH
Intrusion detection with Tripwire
Firewalld – zone, service, and port management
Removing Firewalld and returning to iptables
Summary
References
8. Troubleshooting Database Services
Getting up-and-running with MariaDB
Resetting and recovering a root password with MariaDB
Tuning MariaDB and MySQL
Obtaining metrics from MariaDB and MySQL
Returning to MySQL
Installing and configuring PostgreSQL 9
Summary
References
9. Troubleshooting Web Services
Auditing the server with cURL
Debugging Akamai headers with cURL
Adding Varnish to Apache
Testing Varnish with cURL
Using cURL to access an FTP directory
Enabling mod_status in Apache
Summary
References
10. Troubleshooting DNS Services
Changing the hostname and managing the FQDN
Performing system sanity checks with BIND
Monitoring bandwidth with iftop
Flushing the cache
Summary
References
Index
Troubleshooting CentOS
Copyright © 2015 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.
Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.
Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.
First published: June 2015
Production reference: 1220615
Published by Packt Publishing Ltd.
Livery Place
35 Livery Street
Birmingham B3 2PB, UK.
ISBN 978-1-78528-982-8
www.packtpub.com
Credits
Author
Jonathan Hobson
Reviewers
Mohamed Alibi
Toni de la Fuente
Commissioning Editor
Neil Alexander
Acquisition Editor
Usha Iyer
Content Development Editor
Anand Singh
Technical Editors
Dhiraj Chandanshive
Pramod Kumavat
Copy Editors
Janbal Dharmaraj
Rashmi Sawant
Project Coordinator
Vijay Kushlani
Proofreader
Safis Editing
Indexer
Hemangini Bari
Production Coordinator
Shantanu N. Zagade
Cover Work
Shantanu N. Zagade
About the Author
Jonathan Hobson is a professional Dev/Ops engineer who provides round-the-clock application and server support to one of the world's largest online newspapers. He has been using CentOS since its inception, and as the author of the best-selling CentOS 6 Linux Server Cookbook, Packt Publishing (ISBN-13: 978-1849519021), Jonathan maintains a strong reputation for the generation of ideas, problem solving, building business confidence, and finding innovative solutions in challenging environments.
Jonathan has worked in a variety of environments, and with more than 20 years of experience as a professional developer, database administrator, and server engineer, he continues to support the open source community at large.
Following a wide range of interests beyond the computer screen, Jonathan also enjoys walking his dogs and gett...