Introduction to the Azure Desired State Configuration extension handler

Note

Before you enable DSC Extension, we would like you to know that a newer version of DSC is now generally available, named Azure Machine Configuration. The Azure Machine Configuration service includes features from DSC Extension and commonly requested features from customer feedback. Azure Machine Configuration also includes hybrid machine support through Arc-enabled servers.

The Azure VM Extension for Azure virtual machines (VM) and the associated extensions are part of Microsoft Azure infrastructure services. Azure VM extensions are software components that extend VM functionality and simplify various VM management operations.

The DSC extension only pushes a configuration to the VM. No ongoing reporting is available, other than locally in the VM.

Available DSC versions

The DSC extension supports configurations from version 1.1 of the DSC platform. For more information, see PSDesiredStateConfiguration v1.1.

Prerequisites

• Developer workstation: To interact with the Azure DSC extension, you must use either the Azure portal or the Azure PowerShell/CLI SDK.

• Guest agent: The Azure VM that's prepared by the DSC configuration must use an operating system that supports Windows Management Framework (WMF) 4.0 or later. For the full list of supported operating system versions, see the Azure DSC extension version history.

Terms and concepts

This article assumes familiarity with the following concepts:

• Configuration refers to a DSC configuration document.

• Node identifies a target for a DSC configuration. In this article, node always refers to an Azure VM.

• Configuration data is stored in a PowerShell DSC format file (.psd1) that has environmental data for a configuration.

Architecture

The Azure DSC extension uses the Azure VM Extension framework to deliver, enact, and report on DSC configurations running on Azure VMs. The DSC extension accepts a configuration document and a set of parameters.

When the extension is called the first time, it installs a version of WMF by using the following logic:

• If the Azure VM operating system is Windows Server 2016, no action is taken. Windows Server 2016 already has the latest version of PowerShell installed.

• If the wmfVersion property is specified, the specified version of WMF is installed, unless the specified version is incompatible with the operating system on the VM.

• If no wmfVersion property is specified, the latest applicable version of WMF is installed.

The WMF installation process requires a restart. After you restart, the extension downloads the .zip file that's specified in the modulesUrl property, if provided. If this location is in Azure Blob Storage, you can specify an SAS token in the sasToken property to access the file. After the .zip downloads and unpacks, the configuration function defined in configurationFunction runs to generate a Managed Object Format (MOF) file (.mof). The extension then runs the Start-DscConfiguration -Force command by using the generated .mof file. The extension captures output and writes it to the Azure status channel.

Node configuration name

For the NodeConfigurationName parameter, be sure to provide the name of the node configuration and not the Configuration.

The Configuration is defined in a script that's used to compile the node configuration (MOF file). The name of the node configuration is always the name of the Configuration followed by a period . and either localhost or a specific computer name.

ARM template deployment

The most common approach for deploying the DSC extension is to use Azure Resource Manager templates. For more information and for examples of how to include the DSC extension in ARM templates, see Desired State Configuration extension with ARM templates.

PowerShell cmdlet deployment

PowerShell cmdlets for managing the DSC extension are ideal for interactive troubleshooting and information-gathering scenarios. You can use the cmdlets to package, publish, and monitor DSC extension deployments.

Here are some of the PowerShell cmdlets that are available:

• The Publish-AzVMDscConfiguration cmdlet takes in a configuration file, scans it for dependent DSC resources, and then creates a .zip file. The .zip file contains the configuration and DSC resources that are needed to enact the configuration. The cmdlet can also create the package locally by using the -OutputArchivePath parameter. Otherwise, the cmdlet publishes the .zip file to Blob Storage, and then secures it with an SAS token.

  The PowerShell configuration script (.ps1) created by the cmdlet is in the .zip file at the root of the archive folder. The module folder is placed in the archive folder in resources.

• The Set-AzVMDscExtension cmdlet injects the settings that the PowerShell DSC extension requires into a VM configuration object.

• The Get-AzVMDscExtension cmdlet retrieves the DSC extension status of a specific VM.

• The Get-AzVMDscExtensionStatus cmdlet retrieves the status of the DSC configuration that's enacted by the DSC extension handler. This action can be performed on a single VM or a group of VMs.

• The Remove-AzVMDscExtension cmdlet removes the extension handler from a specific VM. Keep in mind that this cmdlet doesn't remove the configuration, uninstall WMF, or change the applied settings on the VM. The cmdlet only removes the extension handler.

Important considerations

There are several considerations to keep in mind when working with Azure Resource Manager cmdlets.

• Azure Resource Manager cmdlets are synchronous.

• Several parameters are required, including ResourceGroupName, VMName, ArchiveStorageAccountName, Version, and Location.

• ArchiveResourceGroupName is an optional parameter. Specify this parameter when your storage account belongs to a different resource group than the one where the VM is created.

• Use the AutoUpdate switch to automatically update the extension handler to the latest version when it's available. This parameter has the potential to cause restarts on the VM when a new version of WMF is released.

Configuration with PowerShell cmdlets

The Azure DSC extension can use DSC configuration documents to directly configure Azure VMs during deployment. This step doesn't register the node to Automation or Machine Configuration. Keep in mind that the node isn't centrally managed.

The following code shows a simple example configuration. To work with this example, save this configuration locally as the iisInstall.ps1 script file.

configuration IISInstall
{
    node "localhost"
    {
        WindowsFeature IIS
        {
            Ensure = "Present"
            Name = "Web-Server"
        }
    }
}

The following PowerShell commands place the iisInstall.ps1 script on the specified VM. The commands also execute the configuration, and then report back on status.

$resourceGroup = 'dscVmDemo'
$vmName = 'myVM'
$storageName = 'demostorage'
#Publish the configuration script to user storage
Publish-AzVMDscConfiguration -ConfigurationPath .\iisInstall.ps1 -ResourceGroupName $resourceGroup -StorageAccountName $storageName -force
#Set the VM to run the DSC configuration
Set-AzVMDscExtension -Version '2.76' -ResourceGroupName $resourceGroup -VMName $vmName -ArchiveStorageAccountName $storageName -ArchiveBlobName 'iisInstall.ps1.zip' -AutoUpdate -ConfigurationName 'IISInstall'

Azure CLI deployment

The Azure CLI can be used to deploy the DSC extension to an existing VM. The following examples show how to deploy a VM on Windows.

For a VM running Windows, use the following command:

az vm extension set \
  --resource-group myResourceGroup \
  --vm-name myVM \
  --name DSC \
  --publisher Microsoft.Powershell \
  --version 2.77 --protected-settings '{}' \
  --settings '{}'

Azure portal deployment

To set up the DSC extension in the Azure portal, follow these steps:

1. Go to a VM.

2. Under Settings, select Extensions + Applications.

3. Under Extensions, select + Add.

4. Select PowerShell Desired State Configuration, then select Next.

5. Configure the following parameters for the DSC extension.

   • Configuration Modules or Script: (Required) Provide the Configuration modules or script file for your VM.

     Configuration modules and scripts require a .ps1 file that has a configuration script or a .zip file with a .ps1 configuration script at the root. If you use a .zip file, all dependent resources must be included in module folders in the .zip file. You can create the .zip file by using the Publish-AzureVMDscConfiguration -OutputArchivePath cmdlet that's included in the Azure PowerShell SDK. The .zip file is uploaded to your user Blob Storage and secured by an SAS token.

   • Module-qualified Name of Configuration: (Required) Specify this setting to include multiple configuration functions in a single .ps1 script file. For this setting, enter the name of the configuration .ps1 script file followed by a slash \ and then the name of the configuration function. For example, if the .ps1 script file has the name configuration.ps1 and the configuration name is IisInstall, enter the value configuration.ps1\IisInstall for the setting.

   • Configuration Arguments: If the configuration function takes arguments, enter the values by using the format argumentName1=value1,argumentName2=value2. Notice that this format differs from the format that's used to specify configuration arguments in PowerShell cmdlets or ARM templates.

   • Configuration Data PSD1 File: If your configuration requires a configuration data file in .psd1 format, use this setting to select the data file and upload it to your user Blob Storage. The configuration data file is secured with an SAS token in Blob Storage.

   • WMF Version: Specify the version of Windows Management Framework to install on your VM. If you choose latest, which is the default value, the system installs the most recent version of WMF. Other possible values include 4.0, 5.0, and 5.1. The possible values are subject to updates.

   • Data Collection: Enable this setting if you want the DSC extension to collect telemetry about your VM. For more information, see Azure DSC extension data collection.

   • Version: (Required) Specify the version of the DSC extension to install. For information about versions, see Azure DSC extension version history.

   • Auto Upgrade Minor Version: This setting maps to the AutoUpdate switch in the cmdlets. Configure this setting to enable the DSC extension to automatically update to the latest version during installation. Yes instructs the DSC extension handler to use the latest available version. No (default) forces installation of the version you specify in the Version setting.

6. After you configure the parameters, select Review + Create, and then select Create.

DSC extension logs

You can view logs for the Azure DSC extension on the VM under C:\WindowsAzure\Logs\Plugins\Microsoft.Powershell.DSC\<version number>.

Next steps

• For more information about PowerShell DSC, go to the PowerShell documentation center.
• Examine the ARM template for the Azure DSC extension.
• For more functionality that you can manage by using PowerShell DSC, and for more DSC resources, browse the PowerShell gallery.
• For details about passing sensitive parameters into configurations, see Manage credentials securely with the Azure DSC extension handler.