If you’ve been following my recent posts, you know that the PowerShell Summit North America 2015 is only days away. I’ve used April to learn (as much as I can) about DSC. I wasn’t completely new to it — I’ve been following along for a bit — but there is still plenty I didn’t know, or at least haven’t experienced hands-on. Anyway, I’m doing whatever I can to absorb as much DSC knowledge as possible, before next week.

While I only have a single target node at this point, I stopped and wondered how obnoxious it may be to determine the GUID to node mapping, when I update a configuration script. I know I can get it from the target node, by using Get-DscLocalConfigurationManager, but what’s an easier way to get them all, at once? While I could query all the nodes, I figured I can also query my MOFs’ directory, providing we trust that source, and why shouldn’t we.

I wrote out a quick and dirty function that I’ve included below. Point this function at your MOFs’ directory on your DSC Pull Server and ta-da, it’ll create a PSCustomObject with your node names and matching GUIDs.

Disclaimer: I’m still learning DSC and may one day realize this function was a waste of time.

Function Get-TMDSCGuid {
    [CmdletBinding()]
    Param (
        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    Begin {
        Write-Verbose -Message 'Collecting MOF files.'
        try {
            $Files = Get-ChildItem -Path $Path -Filter '*.mof' -ErrorAction Stop | Select-Object -Property *
        } catch [System.Management.Automation.ItemNotFoundException] {
            Write-Warning -Message "This path does not exist: $Path"
        }
    } # End Begin.

    Process {
        If ($Files) {
            Write-Verbose -Message 'Checking MOF files.'
            Write-Verbose -Message 'Writing ComputerName-GUID Mappings.'
            ForEach ($File in $Files) {
                $ComputerName = $null
                try {
                    $ComputerName = (Get-Content -Path $File.FullName |
                        Where-Object {$PSItem -like '@TargetNode*'}).Split('=')[-1].Trim("'")
                } catch {
                    $NoTargetNode += "$($File.Name);"
                } # End Try-Catch.

                If ($ComputerName) {
                    $Object = [pscustomobject]@{
                        ComputerName = $ComputerName
                        Guid = $File.BaseName
                    }
                    Write-Output -Verbose $Object
                } # End If.
            } # End ForEach.

            If ($NoTargetNode) {
                Write-Verbose -Message "---MOF Files without @TargetNode section---"
                $NoTargetNode = ($NoTargetNode.Trim(';')).Split(';')
                ForEach ($Node in $NoTargetNode) {
                    Write-Verbose -Message ($Node)
                } # End ForEach.
            } # End If.
        } Else {
            Write-Verbose -Message 'Cannot locate any MOF files.'
        }
    } # End Process.

    End {
        Write-Verbose -Message 'Function is done running.'
    } # End End.
} # End Function.

Below is an example of the output that will be displayed when we invoke the function against the directory that holds our <guid>.mof files for our DSC Pull Server.

ComputerName                                                       Guid
------------                                                       ----
serverX.mydomain.com                                               2766ffba-0c66-4358-8426-1a216c2b9d25
serverY.mydomain.com                                               7699bbcd-1a32-1429-9831-0f197d3a9b14
serverZ.mydomain.com                                               3224abda-2b41-4925-2948-4c317a1c0a54