Nagios Core Administration Cookbook Second Edition

Nagios Core Administration Cookbook Second Edition - Second Edition

By : Tom Ryder

Buy this Book

Nagios Core Administration Cookbook Second Edition - Second Edition

By: Tom Ryder

Buy this Book

Overview of this book

Nagios Core is an open source monitoring framework suitable for any network that ensures both internal and customer-facing services are running correctly and manages notification and reporting behavior to diagnose and fix outages promptly. It allows very fine configuration of exactly when, where, what, and how to check network services to meet both the uptime goals of your network and systems team and the needs of your users. This book shows system and network administrators how to use Nagios Core to its fullest as a monitoring framework for checks on any kind of network services, from the smallest home network to much larger production multi-site services. You will discover that Nagios Core is capable of doing much more than pinging a host or to see whether websites respond. The recipes in this book will demonstrate how to leverage Nagios Core's advanced configuration, scripting hooks, reports, data retrieval, and extensibility to integrate it with your existing systems, and to make it the rock-solid center of your network monitoring world.

Nagios Core Administration Cookbook Second Edition

Credits

About the Author

About the Reviewer

www.PacktPub.com

Preface

Free Chapter

Understanding Hosts, Services, and Contacts

Introduction

Creating a new network host

Creating a new HTTP service

Creating a new e-mail contact

Verifying configuration

Creating a new hostgroup

Creating a new servicegroup

Creating a new contactgroup

Creating a new time period

Running a service on all hosts on a group

Working with Commands and Plugins

Creating a new command

Customizing an existing command

Using an alternative check command for hosts

Writing a new plugin from scratch

Implementing threshold checks in a plugin

Using macros as environment variables in a plugin

Working with Checks and States

Introduction

Specifying how frequently to check a host or service

Changing thresholds for PING RTT and packet loss

Changing thresholds for disk usage

Scheduling downtime for a host or service

Managing brief outages with flapping

Adjusting flapping percentage thresholds for a service

Configuring Notifications

Introduction

Configuring notification periods

Configuring notifications for groups

Choosing states for notification

Specifying the number of failed checks before notification

Automating contact rotation

Defining an escalation for repeated notifications

Defining a custom notification method

Filtering notifications based on a host or service value

Monitoring Methods

Introduction

Monitoring PING for any host

Monitoring SSH for any host

Checking an alternative SSH port

Monitoring mail services

Monitoring web services

Checking that a website returns a given string

Monitoring database services

Monitoring the output of an SNMP query

Monitoring a RAID or other hardware device

Creating an SNMP OID for monitoring

Enabling Remote Execution

Introduction

Monitoring local services on a remote machine with NRPE

Setting the listening address for NRPE

Setting allowed client hosts for NRPE

Creating new NRPE command definitions securely

Giving limited sudo(8) privileges to NRPE

Using check_by_ssh with key authentication instead of NRPE

Using check_mk instead of NRPE

Using the Web Interface

Introduction

Using the Tactical Overview

Viewing and interpreting availability reports

Viewing and interpreting trends

Viewing and interpreting notification history

Adding comments on hosts or services in the web interface

Viewing configuration in the web interface

Scheduling checks from the web interface

Acknowledging a problem via the web interface

Managing Network Layout

Introduction

Creating a network host hierarchy

Using the network map

Choosing icons for hosts

Establishing a host dependency

Establishing a service dependency

Monitoring individual nodes in a cluster

Using the network map as an overlay

Managing Configuration

Introduction

Grouping configuration files in directories

Keeping a configuration under version control

Configuring host roles using groups

Building groups using regular expressions

Using inheritance to simplify configuration

Defining macros in a resource file

Using another object's directives in a host or service check

Using custom directives

Dynamically building host definitions

Security and Performance

Introduction

Using authentication for the Nagios Core web interface

Using authenticated contacts

Writing debugging information to the Nagios log file

Monitoring Nagios performance with nagiostats

Setting up a redundant monitoring host

Automating and Extending Nagios Core

Introduction

Allowing and submitting passive checks

Submitting passive checks from a remote host with NSCA

Submitting passive checks in response to SNMP traps

Setting up an event handler script

Tracking host and service states with Nagiosgraph

Reading status in a MySQL database with NDOUtils

Reading status from a Unix socket with MK Livestatus

Writing customized Nagios Core reports

Getting extra visualizations with NagVis

Writing custom Nagios Core management scripts

Index

Customer Reviews

5 star

4 star

3 star

2 star

1 star

Creating a new hostgroup

In this recipe, you'll learn how to create a new hostgroup; in this case, to group two web servers together. It is useful to have distinct groups of hosts that might have different properties, such as being monitored by different teams or running different types of monitored services. It also allows us to view a group breakdown in the Nagios Core web interface and to apply a single service to a whole group of hosts rather than doing so individually. This means that all we would have to do to get a new host monitored in the same way as all the other hosts would be to add it to the group, rather than having to specify the configuration manually.

Getting ready

You should have a working Nagios Core 4.0 or better server running with a web interface.

You should also have at least two hosts that form a meaningful group; perhaps they're similar kinds of servers, such as web servers, or are monitored by the same team, or both at a physical location.

In this example, we have two web servers, sparta.example.net and athens.example.net, and we're going to add them to a group called webservers.

How to do it...

We can add our new hostgroup webservers to the Nagios Core configuration as follows:

Create a new file called /usr/local/nagios/etc/objects/hostgroups.cfg, if it doesn't already exist:
```
# cd /usr/local/nagios/etc/objects
# vi hostgroups.cfg
```
Write the following code into the new file, substituting the names in bold to suit your own layout:
```
define hostgroup {
 hostgroup_name  webservers
 alias           Webservers with Greek names
}
```
Move a directory up and then edit the nagios.cfg file:
```
# cd ..
# vi nagios.cfg
```

Add this line to the end of the file:

cfg_file=/usr/local/nagios/etc/objects/hostgroups.cfg

For each of the hosts we want to add to the group, find their definitions and add a hostgroups directive to put them into the new hostgroup. In this case, our definitions for sparta.example.net and athens.example.net ends up looking like this:

define host {
    use         linux-server
    host_name   sparta.example.net
    alias       sparta
    address     192.0.2.21
    hostgroups  webservers
}
define host {
    use         linux-server
    host_name   athens.example.net
    alias       athens
    address     192.0.2.22
    hostgroups  webservers
}

Restart Nagios:
```
# /etc/init.d/nagios reload
```

We should now be able to visit the Host Groups section of the web interface and see a new hostgroup with two members:

How it works...

The preceding configuration that we have added includes a new file with a new hostgroup into the Nagios Core configuration and inserts appropriate hosts into the group. The hostgroup creates a separate section in the web interface for us to get a quick overview of only the hosts in that particular group.

There's more...

The way we've added hosts to the preceding groups is actually not the only way to do it. If we prefer, we can instead name the hosts for the group inside the group definition, using the members directive, so we could have something like the following:

define hostgroup {
    hostgroup_name  webservers
    alias           Webservers with Greek names
    members         athens.example.net,sparta.example.net
}

We can also make a hostgroup that always includes every single host, if we find that useful:

define hostgroup {
    hostgroup_name  all
    alias           All hosts
    members         *
}

If we're going to be using hostgroups extensively in our Nagios Core configuration to add hosts to groups, we should use whichever of the two methods we think is going to be easiest for us to maintain.

It's worth noting that a host can be in more than one group and there is no limit on the number of groups we can declare, so we can afford to be quite liberal with how we group our hosts into any sort of useful categories. examples of hostgroups could be organizing servers by a function, manufacturer, or colocation customer or organizing routers by BGP or OSPF usage; it all depends on what kind of network we're monitoring.

Nagios Core Administration Cookbook Second Edition - Second Edition

By : Tom Ryder

Nagios Core Administration Cookbook Second Edition - Second Edition

By: Tom Ryder

Overview of this book

Related Content you might be interested in

Current Title:

Nagios Core Administration Cookbook Second Edition - Second Edition

Creating a new hostgroup

Getting ready

How to do it...

How it works...

There's more...

See also