Applying a snapshot–via PowerShell [Hyper-V]

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Ben Armstrong [MSFT]

19 Oct 2011 10:08 AM

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Now that we know how to take a snapshot, and how to list snapshots – let’s start applying snapshots:

# Function for handling WMI jobs / return values

Function ProcessResult($result, $successString, $failureString)

{

   #Return success if the return value is "0"

   if ($result.ReturnValue -eq 0)

      {write-host $successString} 

   #If the return value is not "0" or "4096" then the operation failed

   ElseIf ($result.ReturnValue -ne 4096)

      {write-host $failureString " Error value:" $result.ReturnValue}

   Else

      {#Get the job object

      $job=[WMI]$result.job

      #Provide updates if the jobstate is "3" (starting) or "4" (running)

      while ($job.JobState -eq 3 -or $job.JobState -eq 4)

         {write-host $job.PercentComplete "% complete"

          start-sleep 1

          #Refresh the job object

          $job=[WMI]$result.job}

       #A jobstate of "7" means success

       if ($job.JobState -eq 7)

          {write-host $successString

          return $true}

       Else

          {write-host $failureString

          write-host "ErrorCode:" $job.ErrorCode

          write-host "ErrorDescription" $job.ErrorDescription

          return $false}

       }

}

# Prompt for the Hyper-V Server to use

$HyperVServer = Read-Host "Specify the Hyper-V Server to use (enter '.' for the local computer)"

# Prompt for the virtual machine to use

$VMName = Read-Host "Specify the name of the virtual machine"

# Prompt for the name of the snapshot to apply

$SnapshotName = Read-Host "Specify the name of the snapshot to apply"

# Get the management service

$VMMS = gwmi -namespace root\virtualization Msvm_VirtualSystemManagementService -computername $HyperVServer

# Get the virtual machine object

$VM = gwmi MSVM_ComputerSystem -filter "ElementName='$VMName'" -namespace "root\virtualization" -computername $HyperVServer

# Find the snapshot that we want to apply

$Snapshot = gwmi -Namespace root\virtualization -Query "Associators Of {$VM} Where AssocClass=Msvm_ElementSettingData ResultClass=Msvm_VirtualSystemSettingData" | where {$_.ElementName -eq $SnapshotName} | select -first 1

# Apply the snapshot

$result = $VMMS.ApplyVirtualSystemSnapshot($VM, $Snapshot)

# Check to make sure we succeeded

$applySucceeded = ProcessResult $result "Snapshot applied." "Failed to apply snapshot."

This is a fairly standard Hyper-V WMI script. One thing to be aware of is that this operation will fail if the virtual machine is running when you try to apply the snapshot – the virtual machine needs to be turned off or put into a saved state first.

Cheers,
Ben

Attachment:

ApplySnapshot.zip