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
About the Author
About the Reviewers

Re-adding the drives to the arrays

The /dev/sdb disk seems to be functional and, outside the event count difference, we cannot see any reason the RAID would reject the devices. Our next step will be an attempt to re-add the removed devices to their RAID arrays.

The first RAID we will attempt this with is /dev/md127:

[nfs]# mdadm --detail /dev/md127
        Version : 1.0
  Creation Time : Wed Apr 15 09:39:22 2015
     Raid Level : raid1
     Array Size : 511936 (500.02 MiB 524.22 MB)
  Used Dev Size : 511936 (500.02 MiB 524.22 MB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Mon May 11 04:08:10 2015
          State : clean, degraded 
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           Name : localhost:boot
           UUID : 7adf0323:b0962394:387e6cd0:b2914469
         Events : 60

    Number   Major   Minor   RaidDevice State
       0       8        1   ...