DevOps Troubleshooting: Linux Server Best Practices

Description

An expert on Linux gathers standardized, repeatable techniques used to solve Linux server problems. 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 A B C D E F G H I L M N O P Q R S T U V W Z