Skip to main content

Desired State Configuration with Powershell

At TechEd North America 2013 Microsoft has shed some light on the upcoming release of Powershell Version 4. The big news is the DSC or Desired State Configuration feature. Though I should just make a few comments about it.

What is it?

With DSC you can apply a configuration to your servers/datacenter i matter of minutes from powershell. DSC does not have any dependencies of the underlying infrastructure, however it is a tool to configure it. The scope of the DSC can be a server, a collection of servers or other infrastructure items.

How is it delivered?

DSC support both PUSH and PULL configurations. You can apply an configuration with a script that targets specific objects (PUSH) or you can provide an URI to the configuration and the scoped selection and the targets will download the configuration from there (PULL) at scheduled intervals which also can be configured. If you use a PULL model, you must configure your target nodes with an URI and an UUID. 

How do you write it?

You use a declarative syntax to express the state of operating system features. Each feature requires an provider. You can easily write an provider with powershell. I also expect it to be possible to write a provider from Visual Studio. Currently only a few providers exist, however I expect this to change dramatically over the next moths while we wait for the final release of the product.

Operating systems supported?

We expect Powershell V4 to be preinstalled on Windows Server 2012 R2 and Windows 8.1. It is also highly likely that the distribution channel for V4 will be the Windows Management Framework. Further it has been an tradition from Microsoft to support the current release of the operating system and 2 back. This way V4 will be supported in Windows server 2008 R2, Windows 7 and Windows 8 if Microsoft decides to follow their tradition. This implies that Windows 2008 servers are falling behind, as is to be expected. 

How does DSC work?

Using the declarative syntax powershell compiles your script to a MOF-file. You then apply the MOF to your datacenter/servers. When the target system applies an MOF, it checks to see it has all the modules required by the MOF and apply the configuration described in the MOF. When used in combination with the PULL model, the target will automatically try and download any missing modules/providers, extract it to the correct location and finally run them. 

My 2 cents

The linux guys has been enjoying this for years with puppet/chef. I am really excited about this as it will be an turning point in how we apply configuration across different scopes of servers. In software development I see a huge potential as your application evolves through the different stages (Development-, test- and production environment). 

I will definitely write more when I can get my hands on a preview of 2012 R2.   

You can watch a demo here: 


Popular posts from this blog

Serialize data with PowerShell

Currently I am working on a big new module. In this module, I need to persist data to disk and reprocess them at some point even if the module/PowerShell session was closed. I needed to serialize objects and save them to disk. It needed to be very efficient to be able to support a high volume of objects. Hence I decided to turn this serializer into a module called HashData. Other Serializing methods In PowerShell we have several possibilities to serialize objects. There are two cmdlets you can use which are built in: Export-CliXml ConvertTo-JSON Both are excellent options if you do not care about the size of the file. In my case I needed something lean and mean in terms of the size on disk for the serialized object. Lets do some tests to compare the different types: (Hashdata.Object.ps1) You might be curious why I do not use the Export-CliXML cmdlet and just use the [System.Management.Automation.PSSerializer]::Serialize static method. The static method will generate t

Toying with audio in powershell

Controlling mute/unmute and the volume on you computer with powershell. Add-Type -TypeDefinition @' using System.Runtime.InteropServices; [Guid("5CDF2C82-841E-4546-9722-0CF74078229A"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] interface IAudioEndpointVolume { // f(), g(), ... are unused COM method slots. Define these if you care int f(); int g(); int h(); int i(); int SetMasterVolumeLevelScalar(float fLevel, System.Guid pguidEventContext); int j(); int GetMasterVolumeLevelScalar(out float pfLevel); int k(); int l(); int m(); int n(); int SetMute([MarshalAs(UnmanagedType.Bool)] bool bMute, System.Guid pguidEventContext); int GetMute(out bool pbMute); } [Guid("D666063F-1587-4E43-81F1-B948E807363F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] interface IMMDevice { int Activate(ref System.Guid id, int clsCtx, int activationParams, out IAudioEndpointVolume aev); } [Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), Inte

Something completely different – PoshARM

I needed a project for my Xmas holiday and I needed something remotely work related. Thus the dubious PoshARM PowerShell module was born and brought to life during my Xmas holiday. Simply put it is a module that lets you build – for now – simple Azure Resource Manager (ARM) templates with PowerShell .  The module can also import templates from a file or from the clipboard/string. Your partial template or ready made template can be exported as a PowerShell script. This blog post will walk you through how to use it and the features that is currently implemented.  Update 08.02.2017: The module is now published to the PowerShellGallery ( ). It is still in beta version, however test coverage have increased and some bugs have been squashed during the testing. Also help is present, however somewhat lacking here and there. Update 18.01.2017: The module is now on GitHub. Here is the link to the repro  ( PoshARM on GitHub ) What