Extending Hyper-V with PowerShell

Lately I've been writing about my use of PowerShell type extensions as a way to get more done quickly. Or at least give me the information I want with minimal effort. I use Hyper-V a great deal and the Hyper-V cmdlets are invaluable. And while a command like Get-VM provides a lot of information, I always seem to want more so I thought I'd share with you my Hyper-V related type extensions. Even if you don't need or use Hyper-V, you might find my techniques useful.

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The object type for a Hyper-V virtual machine is Microsoft.HyperV.PowerShell.VirtualMachine which you can get easily enough by running Get-VM and piping it to Get-Member. Using Update-TypeData, there are a number of script properties I want to define. These are properties where the value is calculated by a PowerShell script block. For example, I want to be able to quickly see if a virtual machine is missing any of its configured disk files. I could run a command like this:

But if I want this information often, that's too much typing. So instead I can create a script property with this script block. This version takes into account that the VM might have multiple disks, one or more of which might be missing.

{
    if ($this.HardDrives) {
        #test if there are any false results
        if ( ($this | Get-VMHardDiskDrive | Test-Path) -contains $False ) {
            $False
        }
        else {
            $True
        }
    }
    else {
        #no hard drive files configured or found
        $false
    }
}

On a related note, I'd like to know how much disk space the virtual machine is consuming.

{ 
 $stat = Get-VMHardDiskDrive -VMName $this.vmname | Get-Item | Measure-Object -Property length -sum
 [math]::Round($stat.sum/1GB,2)
}

I also like to know the path to the configuration file. This will be a vmcx file with a file name that matches the virtual machine's ID.

Join-path -Path "$($this.configurationLocation)\Virtual Machines" -ChildPath "$($this.vmid).vmcx" -Resolve

In order to define these, and a few others, I use code like this in my PowerShell profile script.

I define a hashtable where the key will be the property name and the value is the scriptblock I will use.

$extensions = @{
TestVHD = {
    if ($this.HardDrives) {
        #test if there are any false results
        if ( ($this | Get-VMHardDiskDrive | Test-Path) -contains $False ) {
            $False
        }
        else {
            $True
        }
    }
    else {
        #no hard drive files configured or found
        $false
    } 
}
ConfigurationFile = {
 Join-path -Path "$($this.configurationLocation)\Virtual Machines" -ChildPath "$($this.vmid).vmcx" -Resolve
 } 
Diskpath = {$this.Harddrives.path}
Running = { if ($this.state -eq 'Running') {$True} else { $False}}
SizeGB = { 
 $stat = Get-VMHardDiskDrive -VMName $this.vmname | Get-Item | Measure-Object -Property length -sum
 [math]::Round($stat.sum/1GB,2)
  }
}

Next I define a hashtable of parameters that I will splat with Update-TypeData.

$params = @{
  TypeName = 'Microsoft.HyperV.PowerShell.VirtualMachine' 
  MemberType = 'ScriptProperty'
  MemberName = ''
  Value = ''
  Force = $True
}

The last step is to enumerate the extensions and update type data.

$extensions.GetEnumerator() | foreach {
 $params.memberName = $_.key
 $params.value = $_.value
 # Write-Host "Creating script property $($_.key)" -ForegroundColor cyan
 Update-Typedata @params
}

By using hash tables, my code organized and easier to read.

And now I can run commands like this:

I love that PowerShell provides the flexibility to meet my needs. As always, comments and feedback are welcome.