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Showing content from https://docs.microsoft.com/en-us/powershell/scripting/dsc/configurations/configurations below:

DSC Configurations - PowerShell | Microsoft Learn

Applies To: Windows PowerShell 4.0, Windows PowerShell 5.0

DSC configurations are PowerShell scripts that define a special type of function. To define a configuration, you use the PowerShell keyword Configuration.

Configuration MyDscConfiguration {
    Node "TEST-PC1" {
        WindowsFeature MyFeatureInstance {
            Ensure = 'Present'
            Name = 'RSAT'
        }
        WindowsFeature My2ndFeatureInstance {
            Ensure = 'Present'
            Name = 'Bitlocker'
        }
    }
}
MyDscConfiguration

Save the script as a .ps1 file.

Configuration syntax

A configuration script consists of the following parts:

The Configuration block. This is the outermost script block. You define it by using the Configuration keyword and providing a name. In this case, the name of the configuration is MyDscConfiguration.
One or more Node blocks. These define the nodes (computers or VMs) that you are configuring. In the above configuration, there is one Node block that targets a computer named TEST-PC1. The Node block can accept multiple computer names.
One or more resource blocks. This is where the configuration sets the properties for the resources that it is configuring. In this case, there are two resource blocks, each of which call the WindowsFeature resource.

Within a Configuration block, you can do anything that you normally could in a PowerShell function. In the previous example, if you didn't want to hard code the name of the target computer in the configuration, you could add a parameter for the node name.

In this example, you specify the name of the node by passing it as the ComputerName parameter when you compile the configuration. The name defaults to localhost.

Configuration MyDscConfiguration
{
    param
    (
        [string[]]$ComputerName='localhost'
    )

    Node $ComputerName
    {
        WindowsFeature MyFeatureInstance
        {
            Ensure = 'Present'
            Name = 'RSAT'
        }

        WindowsFeature My2ndFeatureInstance
        {
            Ensure = 'Present'
            Name = 'Bitlocker'
        }
    }
}

MyDscConfiguration

The Node block can also accept multiple computer names. In the above example, you can either use the -ComputerName parameter, or pass a comma-separated list of computers directly to the Node block.

MyDscConfiguration -ComputerName "localhost", "Server01"

When specifying a list of computers to the Node block, from within a Configuration, you need to use array-notation.

Configuration MyDscConfiguration
{
    Node @('localhost', 'Server01')
    {
        WindowsFeature MyFeatureInstance
        {
            Ensure = 'Present'
            Name = 'RSAT'
        }

        WindowsFeature My2ndFeatureInstance
        {
            Ensure = 'Present'
            Name = 'Bitlocker'
        }
    }
}

MyDscConfiguration

Compiling the configuration

Before you can enact a configuration, you have to compile it into a MOF document. You do this by calling the configuration like you would call a PowerShell function. The last line of the example containing only the name of the configuration, calls the configuration.

Note

To call a configuration, the function must be in global scope (as with any other PowerShell function). You can make this happen either by "dot-sourcing" the script, or by running the configuration script by using F5 or clicking on the Run Script button in the ISE. To dot-source the script, run the command . .\myConfig.ps1 where myConfig.ps1 is the name of the script file that contains your configuration.

When you call the configuration, it:

Resolves all variables
Creates a folder in the current directory with the same name as the configuration.
Creates a file named NodeName.mof in the new directory, where NodeName is the name of the target node of the configuration. If there is more than one node, a MOF file will be created for each node.

Note

The MOF file contains all of the configuration information for the target node. Because of this, it's important to keep it secure. For more information, see Securing the MOF file.

Compiling the first configuration above results in the following folder structure:

. .\MyDscConfiguration.ps1
MyDscConfiguration

    Directory: C:\users\default\Documents\DSC Configurations\MyDscConfiguration
Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----       10/23/2015   4:32 PM           2842 localhost.mof

If the configuration takes a parameter, as in the second example, that has to be provided at compile time. Here's how that would look:

. .\MyDscConfiguration.ps1
MyDscConfiguration -ComputerName 'MyTestNode'

    Directory: C:\users\default\Documents\DSC Configurations\MyDscConfiguration
Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----       10/23/2015   4:32 PM           2842 MyTestNode.mof

Using new resources in Your configuration

If you ran the previous examples, you might have noticed that you were warned that you were using a resource without explicitly importing it. Today, DSC ships with 12 resources as part of the PSDesiredStateConfiguration module.

The cmdlet, Get-DscResource, can be used to determine what resources are installed on the system and available for use by the LCM. Once these modules have been placed in $env:PSModulePath and are properly recognized by Get-DscResource, they still need to be loaded within your configuration.

Import-DscResource is a dynamic keyword that can only be recognized within a Configuration block, it is not a cmdlet. Import-DscResource supports two parameters:

ModuleName is the recommended way of using Import-DscResource. It accepts the name of the module that contains the resources to be imported (as well as a string array of module names).
Name is the name of the resource to import. This is not the friendly name returned as "Name" by Get-DscResource, but the class name used when defining the resource schema (returned as ResourceType by Get-DscResource).

For more information on using Import-DSCResource, see Using Import-DSCResource

PowerShell v4 and v5 differences

There are differences in where DSC resources need to be stored in PowerShell 4.0. For more information, see Resource location.