Starting a Hyper-V Virtual Machine

Next in the line up of scripts - another simple one - starting a virtual machine:


 Option Explicit
 Dim WMIService
 Dim VMList
 Dim VMName
 'Specify the name of the virtual machine that I want to start
 VMName = "Windows Server 2003"
 'Get instance of 'virtualization' WMI service on the local computer
 Set WMIService = GetObject("winmgmts:\\.\root\virtualization")
 'Query for the specific virtual machine that I want to start
 Set VMList = WMIService.ExecQuery("SELECT * FROM Msvm_ComputerSystem WHERE ElementName='" & VMName & "'")
 ' Request a state change on the first VM that is returned
 ' 2 = start, 3 = stop and 32769 = save state


 #The name of the virtual machine to be started
 $VMName = "Windows Server 2003"
 #Get the VM Object
 $query = "SELECT * FROM Msvm_ComputerSystem WHERE ElementName='" + $VMName + "'"
 $VM = get-wmiobject -query $query -namespace "root\virtualization" -computername "."
 #Request a state change on the VM
 $Result = $VM.RequestStateChange(2)

Now for some notes:

  • Under VBScript a WMIService.ExecQuery will always return a collection, even if there is only one result.  Using ItemIndex(0) allows you to assume that there is only one item in the collection and just act on it.

  • PowerShell will return a collection for multiple results, but an object if there is a single result.  This can actually be a bit trickier to deal with if you have to handle both.

  • Since I am querying on the element name - it is actually possible to get multiple virtual machines back (you would need to have two virtual machines with the same name for this to happen).  I am not handling this case here.