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Red Hat Enterprise Linux Troubleshooting Guide

You're reading from   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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Product type Paperback
Published in Oct 2015
Publisher
ISBN-13 9781785283550
Length 458 pages
Edition 1st Edition
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Author (1):
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Benjamin Cane Benjamin Cane
Author Profile Icon Benjamin Cane
Benjamin Cane
LinkedIn
Benjamin Cane has nearly 10 years of experience in Linux systems administration. His first systems administration role was in 2006. At that time, he worked for a web hosting company supporting thousands of FreeBSD and Linux systems. Afterwards, he joined a managed services company that specialized in managing mission-critical systems. There, he worked his way to the position of a lead systems engineer, providing 24x7 support for highly critical enterprise systems that ran Red Hat Enterprise Linux. Now, Benjamin is a systems architect. He focuses on building High and Continuous Availability environments within the financial services industry. He is also currently a Red Hat Certified Engineer and Certified Ethical Hacker. With his experience in mission-critical environments, he has learned to identify and troubleshoot very complex issues quickly, because often these environments have a low tolerance for downtime. Being able to identify the root causes of very complex systems issues quickly is a skill that requires extensive knowledge of Linux and troubleshooting best practices. In addition to this book, Benjamin writes about Linux systems administration and DevOps topics on his blog at http://bencane.com. He is also the project founder for Runbook (https://github.com/Runbook/runbook), an open source application designed to monitor and automatically resolve infrastructure and application issues.
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Toc

Table of Contents (14) Chapters Close

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

Back to troubleshooting our RAID

Now that we have a better understanding of RAID and the different configurations, let's go back to investigating our errors.

Apr 26 10:25:44 nfs kernel: md/raid1:md127: Disk failure on sdb1, disabling device.
md/raid1:md127: Operation continuing on 1 devices.

From the preceding error, we can see that our RAID device is md127. We can also see that this device is a RAID 1 device (md/raid1). The message stating Operation continuing on 1 devices means the second part of the mirror is still operational.

The good thing is that, if both sides of the mirror were unavailable, the RAID would completely fail and result in worse issues.

Since we now know the RAID device affected, the type of RAID used, and even the hard disk that failed, we have quite a bit of information about this failure. If we continue looking at the log entries from /var/log/messages, we can find out even more:

Apr 26 10:25:55 nfs kernel: md: unbind<sdb1>
Apr 26 10:25:55 nfs kernel: md: export_rdev...
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Authors (1)

Profile icon Benjamin Cane
Benjamin Cane
LinkedIn icon Github icon
Benjamin Cane has nearly 10 years of experience in Linux systems administration. His first systems administration role was in 2006. At that time, he worked for a web hosting company supporting thousands of FreeBSD and Linux systems. Afterwards, he joined a managed services company that specialized in managing mission-critical systems. There, he worked his way to the position of a lead systems engineer, providing 24x7 support for highly critical enterprise systems that ran Red Hat Enterprise Linux. Now, Benjamin is a systems architect. He focuses on building High and Continuous Availability environments within the financial services industry. He is also currently a Red Hat Certified Engineer and Certified Ethical Hacker. With his experience in mission-critical environments, he has learned to identify and troubleshoot very complex issues quickly, because often these environments have a low tolerance for downtime. Being able to identify the root causes of very complex systems issues quickly is a skill that requires extensive knowledge of Linux and troubleshooting best practices. In addition to this book, Benjamin writes about Linux systems administration and DevOps topics on his blog at http://bencane.com. He is also the project founder for Runbook (https://github.com/Runbook/runbook), an open source application designed to monitor and automatically resolve infrastructure and application issues.
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See other products by Benjamin Cane

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