DevOps Troubleshooting: Linux Server Best Practices

✍ Scribed by Kyle Rankin

• Publisher: Addison-Wesley Professional
• Tongue: English
• Leaves: 235
• Category: Library

✦ Synopsis

An expert on Linux gathers standardized, repeatable techniques used to solve Linux server problems.

✦ Table of Contents

Contents
Preface
Acknowledgments
About the Author
CHAPTER 1 Troubleshooting Best Practices
Divide the Problem Space
Practice Good Communication When Collaborating
Conference Calls
Direct Conversation
Email
Real-Time Chat Rooms
Have a Backup Communication Method
Favor Quick, Simple Tests over Slow, Complex Tests
Favor Past Solutions
Document Your Problems and Solutions
Know What Changed
Understand How Systems Work
Use the Internet, but Carefully
Resist Rebooting
CHAPTER 2 Why Is the Server So Slow? Running Out of CPU, RAM, and Disk I/O
System Load
What Is a High Load Average?
Diagnose Load Problems with top
Make Sense of top Output
Diagnose High User Time
Diagnose Out-of-Memory Issues
Diagnose High I/O Wait
Troubleshoot High Load after the Fact
Configure sysstat
View CPU Statistics
View RAM Statistics
View Disk Statistics
View Statistics from Previous Days
CHAPTER 3 Why Won’t the System Boot? Solving Boot Problems
The Linux Boot Process
The BIOS
GRUB and Linux Boot Loaders
The Kernel and Initrd
/sbin/init
BIOS Boot Order
Fix GRUB
No GRUB Prompt
Stage 1.5 GRUB Prompt
Misconfigured GRUB Prompt
Repair GRUB from the Live System
Repair GRUB with a Rescue Disk
Disable Splash Screens
Can’t Mount the Root File System
The Root Kernel Argument
The Root Device Changed
The Root Partition Is Corrupt or Failed
Can’t Mount Secondary File Systems
CHAPTER 4 Why Can’t I Write to the Disk? Solving Full or Corrupt Disk Issues
When the Disk Is Full
Reserved Blocks
Track Down the Largest Directories
Out of Inodes
The File System Is Read-Only
Repair Corrupted File Systems
Repair Software RAID
CHAPTER 5 Is the Server Down? Tracking Down the Source of Network Problems
Server A Can’t Talk to Server B
Client or Server Problem
Is It Plugged In?
Is the Interface Up?
Is It on the Local Network?
Is DNS Working?
Can I Route to the Remote Host?
Is the Remote Port Open?
Test the Remote Host Locally
Troubleshoot Slow Networks
DNS Issues
Find the Network Slowdown with traceroute
Find What Is Using Your Bandwidth with iftop
Packet Captures
Use the tcpdump Tool
Use Wireshark
CHAPTER 6 Why Won’t the Hostnames Resolve? Solving DNS Server Issues
DNS Client Troubleshooting
No Name Server Configured or Inaccessible Name Server
Missing Search Path or Name Server Problem
DNS Server Troubleshooting
Understanding dig Output
Trace a DNS Query
Recursive Name Server Problems
When Updates Don’t Take
CHAPTER 7 Why Didn’t My Email Go Through? Tracing Email Problems
Trace an Email Request
Understand Email Headers
Problems Sending Email
Client Can’t Communicate with the Outbound Mail Server
Outbound Mail Server Won’t Allow Relay
Outbound Mail Server Can’t Communicate with the Destination
Problems Receiving Email
Telnet Test Can’t Connect
Telnet Can Connect, but the Message Is Rejected
Pore Through the Mail Logs
CHAPTER 8 Is the Website Down? Tracking Down Web Server Problems
Is the Server Running?
Is the Remote Port Open?
Test the Remote Host Locally
Test a Web Server from the Command Line
Test Web Servers with Curl
Test Web Servers with Telnet
HTTP Status Codes
1xx Informational Codes
2xx Successful Codes
3xx Redirection Codes
4xx Client Error Codes
5xx Server Error Codes
Parse Web Server Logs
Get Web Server Statistics
Solve Common Web Server Problems
Configuration Problems
Permissions Problems
Sluggish or Unavailable Web Server
CHAPTER 9 Why Is the Database Slow? Tracking Down Database Problems
Search Database Logs
MySQL
PostgresSQL
Is the Database Running?
MySQL
PostgresSQL
Get Database Metrics
MySQL
PostgresSQL
Identify Slow Queries
MySQL
PostgresSQL
CHAPTER 10 It’s the Hardware’s Fault! Diagnosing Common Hardware Problems
The Hard Drive Is Dying
Test RAM for Errors
Network Card Failures
The Server Is Too Hot
Power Supply Failures
Index
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