Learning Nagios - Third Edition

Cover 1 Copyright 3 Credits 4 About the Authors 5 About the Reviewer 6 www.PacktPub.com 7 Table of Contents 8 Preface 14 Chapter 1: Introducing Nagios 20 Understanding the basics of Nagios 21 Introducing plugins 23 Benefits of monitoring 23 Main features 25 Soft and hard states 27 Summary 28 Chapter 2: Installing Nagios 4 29 Installing Nagios 30 Upgrading from previous versions 30 Performing installation with automated script 31 Installing Nagios using package managers 34 Installation with apt-get/dpkg 34 Installation with yum/rpm 35 Compiling Nagios from source code manually 37 Installing prerequisites 37 Setting up users, groups, and directories 39 Obtaining Nagios and Nagios plugins 41 Compiling and installing Nagios 42 Compiling and installing Nagios plugins 46 Setting up a web server 48 Troubleshooting the web server 50 Running Nagios using virtualizations 53 Running Nagios inside containers 54 Installing Nagios inside virtual machines 56 Summary 57 Chapter 3: Configuring Nagios 59 Configuring Nagios 59 Understanding macro definitions 63 Configuring hosts 67 Configuring host groups 72 Configuring services 74 Configuring service groups 78 Configuring commands 80 Configuring time periods 82 Configuring contacts 85 Configuring contact groups 88 Verifying the configuration 89 Understanding notifications 91 Using inheritance and templates 94 Summary 98 Chapter 4: Using the Built-in Web Interface 99 The Nagios web interface 100 Accessing the web interface 101 Using the web interface 102 Checking the tactical overview 102 Viewing the status map 104 Managing hosts 105 Checking status 105 Viewing host information 107 Managing services 108 Checking status 108 Viewing service information 111 Managing downtimes 112 Checking downtimes statuses 112 Scheduling downtimes 113 Managing comments 114 Nagios information 115 Viewing process information 116 Checking performance information 116 Generating reports 118 Changing the look of the Nagios web interface 120 Summary 125 Chapter 5: Using Additional Interfaces 126 Introducing third-party web interfaces 126 Using Nagios dashboards 127 Installing alternative Nagios web interfaces 128 Viewing performance data with nagiosgraph 132 Learning command-line interfaces 136 Using nagios_commander 137 Interacting with nagios-cli 141 Using mobile applications to check the Nagios status 144 Checking the status on iOS with easyNag 145 Working with Nagios on Android using aNag 148 Checking the status on Windows Phone with NagChecker 150 Summary 152 Chapter 6: Using the Nagios Plugins 153 Understanding checks in Nagios 154 Using standard network plugins 157 Testing the connection to a remote host 157 Testing connectivity using TCP and UDP 158 Monitoring e-mail servers 159 Checking POP3 and IMAP servers 160 Testing SMTP protocol 162 Monitoring network services 163 Checking FTP server 164 Verifying DHCP protocol 165 Monitoring Nagios processes 166 Testing websites 167 Monitoring database systems 170 Checking MySQL 170 Checking PostgreSQL 172 Checking Oracle 173 Checking other databases 174 Monitoring storage space 175 Checking swap space 175 Monitoring disk status SMART 176 Checking disk space 177 Testing free space for remote shares 178 Monitoring resources 179 Checking system load 180 Checking processes 180 Monitoring logged-in users 182 Monitoring other operations 182 Checking for updates with APT 182 Monitoring UPS status 184 Gathering information from LM sensors 184 Using the dummy check plugin 185 Manipulating other plugins' output 186 Additional and third-party plugins 187 Monitoring network software 187 Using third-party plugins 189 Summary 191 Chapter 7: Advanced Configuration 192 Creating maintainable configurations 193 Configuring the file structure 194 Defining object dependencies 196 Creating host dependencies 197 Creating service dependencies 199 Using templates 201 Creating templates 204 Inheriting from multiple templates 205 Using the custom variables 207 Understanding state flapping 209 Summary 212 Chapter 8: Notifications and Events 213 Creating effective notifications 213 Using multiple notifications 214 Sending instant messages via Jabber 216 Notifying users with text messages 217 Integrating with HipChat 219 Slack integration 220 Understanding escalations 222 Setting up escalations 223 Understanding how escalations work 227 Sending commands to Nagios 230 Adding comments to hosts and services 231 Scheduling host and service checks 232 Modifying custom variables 233 Creating event handlers 234 Restarting services automatically 235 Modifying notifications 238 Using adaptive monitoring 240 Summary 243 Chapter 9: Passive Checks and NRDP 244 Understanding passive checks 244 Introducing active and passive checks 245 Configuring passive checks 247 Sending passive check results for hosts 249 Sending passive check results for services 251 Troubleshooting errors 254 Using NRDP 256 Installing the NRDP server 258 Using the NRDP client 260 Securing the NRDP communication 262 Summary 262 Chapter 10: Monitoring Remote Hosts 264 Monitoring over SSH 264 Configuring the SSH connection 266 Using the check_by_ssh plugin 270 Performing multiple checks 274 Troubleshooting the SSH-based checks 278 Monitoring using NRPE 280 Obtaining NRPE 282 Compiling NRPE 283 Configuring the NRPE server 285 Registering NRPE check commands 289 Configuring Nagios for NRPE 291 Using command arguments with NRPE 293 Troubleshooting NRPE 295 Comparing NRPE and SSH 297 Alternatives to SSH and NRPE 298 Summary 299 Chapter 11: Monitoring Using SNMP 300 Introducing SNMP 300 Understanding data objects 304 Working with SNMP and MIB 307 Using graphical tools 311 Setting up an SNMP agent 314 Using SNMP from Nagios 321 Receiving traps 326 Using additional plugins 330 Summary 330 Chapter 12: Advanced Monitoring 332 Monitoring Windows machines 333 Installing NSClient++ 333 Configuring NSClient++ 335 Monitoring Windows using check_nt 338 Performing checks using NRPE protocol 342 Querying WMI data from Nagios 343 Implementing external scripts 345 Understanding distributed monitoring 348 Introducing obsessive notifications 350 Configuring Nagios instances 353 Performing freshness checking 356 Using templates for distributed monitoring 358 Creating the host and service objects 359 Customizing checks with custom variables 362 Summary 363 Chapter 13: Programming Nagios 364 Introducing Nagios customizations 365 Creating custom active checks 367 Testing MySQL database correctness 368 Monitoring local time against a time server 370 Writing plugins the right way 372 Checking websites 376 Writing commands to send notifications 379 Managing Nagios 382 Using passive checks 385 Introducing the query handler 388 Communicating with the query handler 389 Using the query handler programmatically 391 Using the core service 392 Introducing the Nagios event radio dispatcher 395 Summary 397 Index 399 Learn and monitor your entire IT infrastructure to ensure your systems, applications, services, and business function effectively. About This Book • Packed with tips, tricks and illustrations, the book will explain the configuration and monitoring concepts in a simplified manner • Experience the scalability and flexibility of Nagios in a very practical and easy-to-understand approach. • Unleash the power of Nagios Core and Nagios XI 5 to monitor and secure your infrastructure with ease. Who This Book Is For This book is targeted at System Administrators, both, who have no prior knowledge of Nagios as well as readers experienced with it. It not only covers the basics of Nagios but also the advanced features. What You Will Learn • Set up and use the built-in Nagios web interface • Upskill the additional interfaces available for Nagios to monitor your IT infrastructure • Learn how to perform various checks using both, Nagios standard plugins and third-party plugins • Explore the working of notifications and events in Nagios • Familiarize yourself with SNMP and use it for monitoring devices such as routers, switches, modems and printers • Discover how can be Nagios can be customized and tailored to your needs • Get to know more about the entreprise version of Nagios, Nagios XI In Detail Nagios, a powerful and widely used IT monitoring and management software for problem -solving. It detects problems related to your organizations infrastructure and helps in resolving the issue before it impacts the business. Following the success of the previous edition, this book will continue to help you monitor the status of network devices and also notify the system administrators of network problems. Starting with the fundamentals, the book will teach you how to install and configure Nagios for your environment. The book helps you learn how to end downtimes, adding comments and generating reports using the built-in Web interface of Nagios. Moving on, you will be introduced to the third-party web interfaces and applications for checking the status and report specific information. As you progress further in Learning Nagios, you will focus on the standard set of Nagios plugins and also focus on teach you how to efficiently manage large configurations and using templates. Once you are up to speed with this, you will get to know the concept and working of notifications and events in Nagios. The book will then uncover the concept of passive check and shows how to use NRDP (Nagios Remote Data Processor). The focus then shifts to how Nagios checks can be run on remote machines and SNMP (Simple Network Management Protocol) can be used from Nagios. Lastly, the book will demonstrate how to extend Nagios by creating custom check commands, custom ways of notifying users and showing how passive checks and NRDP can be used to integrate your solutions with Nagios. By the end of the book, you will be a competent system administrator who could monitor mid-size businesses or even large scale enterprises. Style and approach This will be a practical learning guide for system administrators which will teach them everything about Nagios along with implementing it for your organization and then ending with securing it. About This BookPacked with tips, tricks and illustrations, the book will explain the configuration and monitoring concepts in a simplified mannerExperience the scalability and flexibility of Nagios in a very practical and easy-to-understand approach.Unleash the power of Nagios Core and Nagios XI 5 to monitor and secure your infrastructure with ease.Who This Book Is ForThis book is targeted at system administrators who have no prior knowledge of Nagios as well as readers experienced with it. It not only covers the basics of Nagios but also the advanced features.What You Will LearnSet up and use the built-in Nagios web interfaceLearn about the additional interfaces available for Nagios to monitor your IT infrastructureLearn how to perform various checks using both Nagios standard plugins and thirdparty pluginsExplore the working of notifications and events in NagiosFamiliarize yourself with SNMP and use it for monitoring devices such as routers, switches, modems, and printersDiscover how Nagios can be customized and tailored to your needsIn DetailLearning Nagios will help you monitor the status of network devices and also notify the system administrators of network problems. Starting with the fundamentals, the book will teach you how to install and configure Nagios for your environment. Moving on, you will be introduced to the third-party web interfaces and applications for checking the status and report specific information. As you progress further through Learning Nagios, you will focus on the standard set of Nagios plugins and also focus on how to efficiently manage large configurations and use templates. Furthermore, you will get to know the concept and workings of notifications and events in Nagios. The book will then uncover the concept of passive check and show how to use NRDP (Nagios Remote Data Processor) and how Nagios checks for remote machines and SNMP (Simple Network Management Protocol).By the end of the book, you will be a competent system administrator who can monitor mid-size businesses or even large-scale enterprises.