Deleting a snapshot sub-tree–via PowerShell [Hyper-V]

Here is a dangerous script!  Given a virtual machine name and a snapshot name, it will delete the specified snapshot *and* any snapshots underneath it in the snapshot tree that Hyper-V manager displays:

 # 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 delete the tree from
 $SnapshotName = Read-Host "Specify the name of the snapshot to delete the tree from (warning - a lot of snapshots will be deleted)"
  
 # 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 delete
 $Snapshot = gwmi -Namespace root\virtualization -Query "Associators Of {$VM} Where AssocClass=Msvm_ElementSettingData ResultClass=Msvm_VirtualSystemSettingData" | where {$_.ElementName -eq $SnapshotName} | select -first 1
  
 # Delete the snapshot
 $result = $VMMS.RemoveVirtualSystemSnapshotTree($Snapshot)
  
 # Check to make sure we succeeded
 $deleteSucceeded = ProcessResult $result "Deleted snapshot tree." "Failed to delete snapshot tree."

Note that this script actually uses a different WMI method to delete the snapshot sub-tree (when compared to deleting a single snapshot).  There is no way to stop the deletion once it is started, and there is no confirmation prompt in this script – so be careful when you use it!

Cheers,
Ben

DeleteSnapshotTree.zip

Comments

• Anonymous
  October 01, 2013
  very useful info and code . Thanks for the post

• Anonymous
  March 06, 2016
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