CONFIGURING YOUR NAGIOS OBJECT DEFINITIONS

In order to configure Nagios to correctly monitor VMs using data only available
from the Hyper-V host machine, you will need to use custom object definitions.

In your Nagios host defintions, for a given VM, you will want to configure two
custom object definitions, _HVHOSTNAME and _HVVMNAME. It should look like this:

    define host{
            use             windows-server  ; Inherit default values from a template
            host_name       vmtest          ; The name we're giving to this host
            alias           VM Test         ; A longer name associated with the host
            address         10.1.2.3        ; IP address of the host
            notification_options    d,r
            _HVHOSTNAME     Merlin          ; The host the VM resides on
            _HVVMNAME       vmtest          ; The name of the virtual machine
            }

If your virtual machines use identical hostnames to VM names (as the VM name is
configured within Hyper-V), you will not need to use the _HVVMNAME object
definition. This object definition exists for scenarios in which a hostname may
differ from the VM name which is configured within Hyper-V.

Now, in your Nagios command definitions, add the following:

    # 'check_hv_nrpe' command definition
    define command{
            command_name    check_hv_nrpe
            command_line    $USER1$/check_nrpe -H $_HOSTHVHOSTNAME$ -c $ARG1$ -a
                $_HOSTHVVMNAME $ARG2$ $ARG3$
    }

This will create a Nagios check, check_hv_nrpe, which utilizes the check_nrpe
command, but points at the host on which a VM resides, rather than at the VM
itself.

CONFIGURING NSCLIENT++ AND CHECK_NRPE FOR CHECK_HVVHM.PS1

NSClient++ has limitations in its support for multiple variables. As such, you
will need to configure variables in a rather specific manner in your nsclient
configuration file (typically nsclient.ini). In the wrapped scripts section of
the nsclient configuration file, add the following:

    ; CHECK HYPER-V VIRTUAL MACHINES
    check_hvvm=check_hvvm.ps1 -vm $ARG1$ -mem $ARG2$ -net $ARG3$

Make sure you have placed check_hvvm.ps1 in the scripts folder on your Hyper-V
server. After this, restart NSClient++.

It is recommended to create a hostgroup in Nagios which contains your Hyper-V
virtual machines. In addition to this host group, you will want to create a
service definition to utilize the check you have previously configured in
NSClient++. You may use the following as a template:

    # Define hostgroup for Hyper-V virtual machines
    
    define hostgroup{
            hostgroup_name  hv-vms
            alias           Hyper-V Virtual Machines
            members         vmtest,vmtest2
            }

    # Services specific to Hyper-V VMs, not specific to Windows/Linux
    
    define service{
            use                     windows-service
            contact_groups          hv-admins
            hostgroup_name          hv-vms
            service_description     VM Memory Usage
            check_command           check_hv_nrpe!check_hvvm!on!on
            notification_options    w,c,r
            }

The order of the arguments in the check command is as follows:

check_hv_nrpe - specify the command to look for in your Nagios config
$ARG1$, check_hvvm - specify the command to use on the remote host
$ARG2$, on - specify whether or not to check dynamic memory usage, can be set
            to "off" if desired.
$ARG3$, on - specify whether or not to check VM network adapters, can be set
            to "off" if desired.
			
A NOTE ON COPY_VHD.PS1 AND HYPER-V EXPORTS

copy_vhd.ps1 utilizes the Export-VM cmdlet. This cmdlet executes a VM export 
using the System account. For this reason, the computer account of the Hyper-V 
host must have write and edit permissions to the target directory. If the 
computer account does not have write permissions to the target directory, the 
export will fail, and the script will log this in Event Viewer.

This introduces an issue in Samba contexts, where, to my knowledge, it is not 
possible to configure computer accounts to have write access to shared folders.
I am not aware of a workaround to this scenario at this time. I will update if 
I find one. Otherwise, an updated script for Samba environments is forthcoming.

Please also be aware that there are better options out there for Hyper-V backup
infrastructure. Using Export-VM for backups is not considered a best practice, 
but in a low- or no-budget environment it can be made to work. This  script has 
been developed for just such an environment.