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

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

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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

Attachment: DeleteSnapshotTree.zip
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  • very useful info and code . Thanks for the post

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