Desired State Configuration is a new feature of PowerShell 4.0 that is included out of the box with Windows 8.1 and Windows Server 2012 R2. This feature can be loaded on down-level clients by installing the Windows Management Framework 4.0.
The way it works is pretty straightforward, PowerShell 4.0 has introduced a few new keywords, one of which is Configuration. If you’ve written any PowerShell functions it operates in a similar fashion as the Function keyword. Within a Configuration you can have one or more Nodes, each Node is defined as either a string “computer name”, or a variable $Computer, or as a GUID. Within each Node you can have 0 or more resources, there are a dozen built-in resources, and you can roll your own. In addition Microsoft has just released a handful of custom resources that I’ve not played with yet.
Here is an overview of the process
- TechNet DSC Library
- MSDN DSC Blog Articles
- TechNet DSC Blog Articles
- PowerShell Custom DSC Resources
The flow is very straightforward, you create a configuration and save it as a ps1. Executing the ps1 creates a new function, named for your configuration in memory. Run this new function and a subfolder is created named for the configuration and inside the folder a .MOF file is created named for the target node.
You will need to run the function in order to create the directory and proper MOF files
BasicWebServer -ComputerName webserver01
To apply that configuration to the local machine you simply run the following
Start-DSCConfiguration -Path .\BasicWebServer
This will run as a job, if you would like to see it happen, you can add –wait and –verbose to the command above and it will display everything it’s doing.
Start-DSCConfiguration -Wait -Verbose -Path .\BasicWebServer
This configuration is stored on the computer and you can test to see if the configuration has drifted any by running the following
It will return True if it’s happy or False if something is missing. This configuration is stored with the computer and survives reboots, so you can always run
That will return a collection of configurations that are to be applied to the computer. If you would like to bring the target node back in line with its configuration you simply run the following
The end result of this command is that your server will now have all the features its supposed to have available again.