So… I have been working on a little VBScript that can:
- take persistent VSS snapshots
- mount them to a folder (from which you can then backup the files)
- unmount VSS snapshots
It relies on vshadow.exe (documentation), part of the Volume Shadow Copy Service SDK 7.2 as available from Microsoft. I've been working with this version: "VSHADOW.EXE 2.2 - Volume Shadow Copy sample client, Copyright (C) 2005 Microsoft Corporation."
Basically, it is a neat little wrapper around these four vshadow commands:
vshadow.exe -q - List all shadow copies in the system
vshadow.exe -p {volume list} - Manages persistent shadow copies
vshadow.exe -el={SnapID},dir - Expose the shadow copy as a mount point
vshadow.exe -ds={SnapID} - Deletes this shadow copy
Here is its help screen:
VSS Snapshot Create/Mount Tool
Usage:
cscript /nologo VssSnapshot.vbs /target:path { /volume:X | /unmount } [/debug]
/volume - drive letter of the volume to snapshot
/target - the path (absolute or relative) to mount the snapshot to
/debug - swich on debug output
Examples:
cscript /nologo VssSnapshot.vbs /target:C:\Backup\DriveD /volume:D
cscript /nologo VssSnapshot.vbs /target:C:\Backup\DriveD /unmount
Hint: No need to unmount before taking a new snapshot.
Here some sample output:
C:\VssSnapshot>cscript /nologo VssSnapshot.vbs /target:MountPoints\E /volume:E
05/03/2010 17:13:04 preparing VSS mount point...
05/03/2010 17:13:04 mount point prepared at: C:\VssSnapshot\MountPoints\E
05/03/2010 17:13:04 creating VSS snapshot for volume: E
05/03/2010 17:13:08 snapshot created with ID: {4ed3a907-c66f-4b20-bda0-9dcda3b667ec}
05/03/2010 17:13:08 VSS snapshot mounted sucessfully
05/03/2010 17:13:08 finished
C:\VssSnapshot>cscript /nologo VssSnapshot.vbs /target:MountPoints\E /unmount
05/03/2010 17:13:35 preparing VSS mount point...
05/03/2010 17:13:36 nothing else to do
05/03/2010 17:13:36 finished
And here is the script itself. The usual disclaimer applies: The software is provided as is, I give no warranties, use at your own risk, if something breaks the only one to blame is yourself. I have tested it quite thoroughly, though and it works fine for me. Feel free to notify me of any bugs via the comments below.
''# VssSnapshot.vbs
''# http://serverfault.com/questions/119120/how-to-use-a-volume-shadow-copy-to-make-backups/119592#119592
Option Explicit
Dim fso: Set fso = CreateObject("Scripting.FileSystemObject")
''# -- MAIN SCRIPT -------------------------------------------
Dim args, snapshotId, targetPath, success
Set args = WScript.Arguments.Named
CheckEnvironment
Log "preparing VSS mount point..."
targetPath = PrepareVssMountPoint(args("target"))
If args.Exists("unmount") Then
Log "nothing else to do"
ElseIf targetPath <> vbEmpty Then
Log "mount point prepared at: " & targetPath
Log "creating VSS snapshot for volume: " & args("volume")
snapshotId = CreateVssSnapshot(args("volume"))
If snapshotId <> vbEmpty Then
Log "snapshot created with ID: " & snapshotId
success = MountVssSnapshot(snapshotId, targetPath)
If success Then
Log "VSS snapshot mounted sucessfully"
Else
Die "failed to mount snapshot"
End If
Else
Die "failed to create snapshot"
End If
Else
Die "failed to prepare mount point"
End If
Log "finished"
''# -- FUNCTIONS ---------------------------------------------
Function PrepareVssMountPoint(target) ''# As String
Dim cmd, result, outArray
Dim path, snapshot, snapshotId
Dim re, matches, match
PrepareVssMountPoint = VbEmpty
target = fso.GetAbsolutePathName(target)
If Not fso.FolderExists(fso.GetParentFolderName(target)) Then
Die "Invalid mount point: " & target
End If
''# create or unmount (=delete existing snapshot) mountpoint
If Not fso.FolderExists(target) Then
If Not args.Exists("unmount") Then fso.CreateFolder target
Else
Set re = New RegExp
re.MultiLine = False
re.Pattern = "- Exposed locally as: ([^\r\n]*)"
cmd = "vshadow -q"
result = RunCommand(cmd, false)
outarray = Split(result, "*")
For Each snapshot In outArray
snapshotId = ParseSnapshotId(snapshot)
If snapshotId <> vbEmpty Then
Set matches = re.Execute(snapshot)
If matches.Count = 1 Then
path = Trim(matches(0).SubMatches(0))
If fso.GetAbsolutePathName(path) = target Then
cmd = "vshadow -ds=" & snapshotId
RunCommand cmd, true
Exit For
End If
End If
End If
Next
If args.Exists("unmount") Then fso.DeleteFolder target
End If
PrepareVssMountPoint = target
End Function
Function CreateVssSnapshot(volume) ''# As String
Dim cmd, result
If Not fso.DriveExists(volume) Then
Die "Drive " & volume & " does not exist."
End If
cmd = "vshadow -p " & Replace(UCase(volume), ":", "") & ":"
result = RunCommand(cmd, false)
CreateVssSnapshot = ParseSnapshotId(result)
End Function
Function MountVssSnapshot(snapshotId, target) ''# As Boolean
Dim cmd, result
If fso.FolderExists(targetPath) Then
cmd = "vshadow -el=" & snapshotId & "," & targetPath
result = RunCommand(cmd, true)
Else
Die "Mountpoint does not exist: " & target
End If
MountVssSnapshot = (result = "0")
End Function
Function ParseSnapshotId(output) ''# As String
Dim re, matches, match
Set re = New RegExp
re.Pattern = "SNAPSHOT ID = (\{[^}]{36}\})"
Set matches = re.Execute(output)
If matches.Count = 1 Then
ParseSnapshotId = matches(0).SubMatches(0)
Else
ParseSnapshotId = vbEmpty
End If
End Function
Function RunCommand(cmd, exitCodeOnly) ''# As String
Dim shell, process, output
Dbg "Running: " & cmd
Set shell = CreateObject("WScript.Shell")
On Error Resume Next
Set process = Shell.Exec(cmd)
If Err.Number <> 0 Then
Die Hex(Err.Number) & " - " & Err.Description
End If
On Error GoTo 0
Do While process.Status = 0
WScript.Sleep 100
Loop
output = Process.StdOut.ReadAll
If process.ExitCode = 0 Then
Dbg "OK"
Dbg output
Else
Dbg "Failed with ERRORLEVEL " & process.ExitCode
Dbg output
If Not process.StdErr.AtEndOfStream Then
Dbg process.StdErr.ReadAll
End If
End If
If exitCodeOnly Then
Runcommand = process.ExitCode
Else
RunCommand = output
End If
End Function
Sub CheckEnvironment
Dim argsOk
If LCase(fso.GetFileName(WScript.FullName)) <> "cscript.exe" Then
Say "Please execute me on the command line via cscript.exe!"
Die ""
End If
argsOk = args.Exists("target")
argsOk = argsOk And (args.Exists("volume") Or args.Exists("unmount"))
If Not argsOk Then
Say "VSS Snapshot Create/Mount Tool" & vbNewLine & _
vbNewLine & _
"Usage: " & vbNewLine & _
"cscript /nologo " & fso.GetFileName(WScript.ScriptFullName) & _
" /target:path { /volume:X | /unmount } [/debug]" & _
vbNewLine & vbNewLine & _
"/volume - drive letter of the volume to snapshot" & _
vbNewLine & _
"/target - the path (absolute or relative) to mount the snapshot to" & _
vbNewLine & _
"/debug - swich on debug output" & _
vbNewLine & vbNewLine & _
"Examples: " & vbNewLine & _
"cscript /nologo " & fso.GetFileName(WScript.ScriptFullName) & _
" /target:C:\Backup\DriveD /volume:D" & vbNewLine & _
"cscript /nologo " & fso.GetFileName(WScript.ScriptFullName) & _
" /target:C:\Backup\DriveD /unmount" & _
vbNewLine & vbNewLine & _
"Hint: No need to unmount before taking a new snapshot." & vbNewLine
Die ""
End If
End Sub
Sub Say(message)
If message <> "" Then WScript.Echo message
End Sub
Sub Log(message)
Say FormatDateTime(Now()) & " " & message
End Sub
Sub Dbg(message)
If args.Exists("debug") Then
Say String(75, "-")
Say "DEBUG: " & message
End If
End Sub
Sub Die(message)
If message <> "" Then Say "FATAL ERROR: " & message
WScript.Quit 1
End Sub
I hope this helps somebody. Feel free to use it in accordance with cc-by-sa. All I ask is that you leave the link intact that points back here.
