Suppose you would like to monitor your Windows systems alongside your Linux systems in Nagios, but want to avoid configuring every single one manually. Also, you want these systems to be removed from Nagios automatically when you decommission them. Puppet, NSClient++, and Chocolatey provide an excellent means for accomplishing this. In this post I will explain how I got this up and running on my CentOS 6 Nagios server.

This article assumes that you’re already using PuppetDB with exported resources in your Puppet environment. As this is outside the scope of this guide, I’m not going to go into how to set this up. However, it is fairly simple to do, especially with the puppetlabs/puppetdb Forge module. If you’re using Puppet Enterprise, you’re likely already using it. This also assumes that you’re using Puppet to manage your Nagios server. In the class that manages your Nagios server, you will need these two lines, to collect the exported resources from your nodes:

  Nagios_host    <<||>> { notify => Service['nagios'] }
  Nagios_service <<||>> { notify => Service['nagios'] }

You will need to ensure that you have Chocolatey available as a package provider for your Windows nodes. My previous post explains how to configure Chocolatey with Puppet. Chocolatey will be used to install NSClient++, which is a monitoring agent for Windows that includes a NRPE server with which Nagios can interface. The documentation on NSClient++ can be found here.

To prepare your Nagios server for managing Windows hosts, first ensure that you have a Nagios command that can initiate NRPE commands against Windows clients. Because the check_nrpe plugin will throw SSL errors against NSClient++, I’ve defined a nagios_command resource like below for Windows systems that does not use SSL:

  nagios_command { 'check_nrpe_win':
    command_name => 'check_nrpe_win',
    command_line => '$USER1$/check_nrpe -H $HOSTADDRESS$ -n -c $ARG1$ -t 30',
  }

Next, define a standard Nagios hostgroup for Windows that includes basic items to check, such as disk space. You may need to alter this for your own environment. I’ve put this under its own class, nagios::server::hostgroup_windows.

class nagios::server::hostgroup_windows {

  nagios_hostgroup { 'windows_hosts':
    alias => 'Windows Hosts',
  }

  nagios_service { 'check_win_cpu':
    check_command       => 'check_nrpe_win!check_cpu',
    use                 => 'generic-service',
    hostgroup_name      => 'windows_hosts',
    notification_period => '24x7',
    service_description => 'CPU Load',
    max_check_attempts  => 3,
  }

  nagios_service { 'check_win_mem':
    check_command       => 'check_nrpe_win!alias_memory',
    use                 => 'generic-service',
    hostgroup_name      => 'windows_hosts',
    notification_period => '24x7',
    service_description => 'Memory Usage',
    max_check_attempts  => 3,
  }

  nagios_service { 'check_win_drives':
    check_command       => 'check_nrpe_win!alias_space',
    use                 => 'generic-service',
    hostgroup_name      => 'windows_hosts',
    notification_period => '24x7',
    service_description => 'Disk Usage',
    max_check_attempts  => 3,
  }

  nagios_service { 'check_rdp':
    check_command       => 'check_rdp',
    use                 => 'generic-service',
    hostgroup_name      => 'windows_hosts',
    notification_period => '24x7',
    service_description => 'RDP',
    max_check_attempts  => 3,
  }

}

Next, create a template for nsclient.ini, which is the main configuration file for NSClient++. The one I’ve created for this guide is relatively simple; you can refer to the NSClient++ documentation for more options. The template, in my case, is located at nagios/templates/nsclient.ini.erb.

[/modules]
CheckSystem=enabled
CheckDisk=enabled
CheckExternalScripts=enabled
NRPEServer=enabled

[/settings/default]
allowed hosts = your_nagios_server_IP

[/settings/NRPE/server]
use ssl = false
allow arguments = true
allow nasty characters = false
port = 5666

[/settings/external scripts/alias]
alias_memory = check_memory "warn=free < 10%" "crit=free < 5%"
alias_space = check_drivesize "warn=free < 10%" "crit=free < 5%" drive=*

Finally, create a class that installs NSClient++ and manages the service on the Windows systems, and exports the nagios_host resource to the Nagios server.

class nagios::windows {

  package { 'nscp':
    ensure   => present,
  }

  service { 'nscp':
    ensure  => running,
    enable  => true,
    require => Package['nscp'],
  }

  file { 'C:/Program Files/NSClient++/nsclient.ini':
    ensure  => file,
    content => template('nagios/nsclient.ini.erb'),
    notify  => Service['nscp'],
  }

  @@nagios_host { $::fqdn:
    ensure             => present,
    alias              => $::hostname,
    address            => $::ipaddress,
    hostgroups         => 'windows_hosts',
    use                => 'generic-host',
    max_check_attempts => 3,
    check_command      => 'check_ping!100.0,20%!500.0,60%',
  }

}

Once you have committed these changes to your Puppet repository, you would then include nagios::windows in the catalog for your Windows host and trigger a Puppet run on it to install NSClient++, enable the service, and export the resource to your Nagios server. Then, execute a Puppet run on your Nagios server. The result should hopefully be like below.

And now your host should be available in Nagios for monitoring.

One additional note: if you include the Windows Hosts host group in the catalog of your Nagios server, you must then have at least one Windows nagios_host exported. Otherwise, Nagios will not start, as it does not allow empty host groups.