Bring on the Scripts!

Bring on the Scripts!

  • Comments 8

Okay! Now that initial documentation of the Hyper-V WMI API is available I thought I would respond with a "Week of Hyper-V Scripts".

Starting with a simple one - here is a script that will list the name, identifier and state for each virtual machine on the physical computer:

VBScript:

Option Explicit
 
Dim WMIService
Dim VMList
Dim VM
 
'Get instance of 'virtualization' WMI service on the local computer
Set WMIService = GetObject("winmgmts:\\.\root\virtualization")
 
'Get all the MSVM_ComputerSystem object
Set VMList = WMIService.ExecQuery("SELECT * FROM Msvm_ComputerSystem")
    
For Each VM In VMList
   if VM.Caption = "Microsoft Virtual Computer System" then
       WScript.Echo "========================================"
       WScript.Echo "VM Name: " & VM.ElementName
       WScript.Echo "VM GUID: " & VM.Name
       WScript.Echo "VM State: " & VM.EnabledState
    end if
Next

PowerShell:

# Get all VM objects on the local computer
$VMs = gwmi -class "MSVM_ComputerSystem" -namespace "root\virtualization" -computername "."
 
foreach ($VM in $VMs){
   if ($VM.Caption -match "Microsoft Virtual Computer System"){
      write-host "=================================="
      write-host "VM Name:  " $VM.ElementName
      write-host "VM GUID:  " $VM.Name
      write-host "VM State: " $VM.EnabledState
   }
}

Now to pull these scripts apart a bit:

  • The flow of these scripts is:
    • Get WMI Service object for virtualization namespace
    • Execute WMI query to get all VM objects
    • Iterate over the VM objects

  • For each virtual machine object we display the "ElementName" - which is the friendly name that you give the virtual machine ("Windows Server Foo") - the "Name" - which is a GUID that is used to internally uniquely identify the virtual machine and the "EnabledState" (you can find what the different EnabledState values mean here: http://msdn2.microsoft.com/en-us/library/cc136822(VS.85).aspx).

  • "gwmi" is PowerShell shorthand for "Get-WMIObject"

  • Amusingly enough this script would also return information about the parent partition (which is technically a virtual machine) which is why I check the caption of the virtual machine and only display information about entries that are actually virtual machines.

Cheers,
Ben

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  • > Amusingly enough this script would also return information about the parent partition (which is technically a virtual machine).

    This is a very questionable design decision - even if all partitions run under the same hypervisor, for the user the host ("parent partition") is a very different thing from a guest ("child partition").

  • > Amusingly enough this script would also return information about the parent partition (which is technically a virtual machine).

    This is a very questionable design decision - even if all partitions run under the same hypervisor, for the user the host ("parent partition") is a very different thing from a guest ("child partition").

    Well, at least with WMI you don't have to do the funny security stuff to write a simple Powershell script.

  • Why you write PowerShell the VBS way?! :(

    gwmi MSVM_ComputerSystem -namespace "root\virtualization" -computername "." |

    where {$_.Caption -eq "Microsoft Virtual Computer System"} |

    Format-List ElementName, Name, EnabledState

  • Thanks - this is great stuff.

    What do you need to run these scripts from a desktop? I'd like to be able to query multiple Hyper-V machines from my desktop.

  • Ben,

    How would I do this WMI via C#? Which Interop DLL would I need to use to get the Hyper-V WMI?

    Thanks

  • Jonathan - The fact that we report the parent is actually to maintain compatibility with the DMTF management standard.

    Xaegr - Sorry, I just find it easier to read this way.

    Jason - You can run this from a remote system without needing to install any thing.  Just change the '.' to the computer name.

    Nehru - You do not need an interop DLL, I will post on this later.

    Cheers,

    Ben

  • Nehru,

    You can do this is managed code like this:

    //Connection credentials to the remote computer - not needed if the logged in account has access

               ConnectionOptions conn = new ConnectionOptions();

               ManagementScope ms = new ManagementScope(@"\\.\root\virtualization", conn);

               //get the computers

               ObjectQuery query = new ObjectQuery("SELECT * FROM Msvm_ComputerSystem");

               //Execute the query  

               ManagementObjectSearcher searcher = new ManagementObjectSearcher(ms, query);

               //Get the results

               ManagementObjectCollection computers = searcher.Get();

               //loop through found computers

               listBox1.Items.Clear();

               foreach (ManagementObject computer in computers)

               {

                   Console.WriteLine(computer["ElementName"].ToString());

               }

  • Ben, we have some custom code written to control VMs on Virtual Server 2005.

    Is there a back words compatibility layer?

    Or does all this code need to be re-written for WMI?

    thanks!

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