Chef Client 11.16.0 gets into PowerShell DSC [feedly]

Chef Client 11.16.0 gets into PowerShell DSC
http://www.getchef.com/blog/2014/09/08/chef-11-16-gets-into-powershell-dsc/

Ohai Chefs. Today's release of Chef Client 11.16.0 marks the inclusion of PowerShell Desired State Configuration (DSC) support into Chef Client for Windows. DSC is a powerful configuration management platform built into PowerShell 4.0, and now you can use it with Chef!

To try it out, just configure a system with Chef Client 11.16.0 or later and target it with a recipe that uses the new dsc_script resource, which you can learn about on our documentation site.

Like Chef, DSC exposes resources to configure systems. The rest of this post gives details on how to use Chef's new dsc_script resource to gain access to all of DSC's resources from your recipes, and also discusses where we're headed with DSC in the future.

The dsc_script resource

The dsc_script resource allows cookbook authors to include DSC configurations in the form of PowerShell code in their Chef recipes. This is not unlike the use of script code through Chef's powershell_script or bash resources. With DSC and dsc_script, however, you get a lot more than just access to a scripting language. Here's a simple example that uses dsc_scriptin a Chef recipe to unzip (i.e. decompress) a file using DSC's Archive resource:

dsc_script 'unzip_powershell_modules' do    code <<-EOH    Archive PSModules      Path = "$home/downloads/modules.zip"      Destination = "$env:programfiles/WindowsPowerShell/Modules"    }  EOH  end

The string supplied to the code attribute above is DSC (and therefore PowerShell) code, which you can learn about at the DSC site. That PowerShell code specifies a "configuration" with DSC'sArchive resource. Running this Chef recipe code will invoke the DSC code and unzip the file located at Path to the directory location at Destination.

Unlike, say, the use of a bash or powershell_script resource in Chef that executes a decompression command like tar, there is no need to write guard expressions (i.e. not_if / only_if) in the recipe when using dsc_script in order to ensure idempotence — DSC resources, like Chef resources, are intrinsically idempotent.

DSC: A new universe of resources for Chef

PowerShell 4.0 ships with 12 built-in resources including Archive, most of which are direct analogs of resources that already exist in Chef. But if you install the recently released DSC Wave 6 resource kit from Microsoft, you suddenly have access to 80+ additional resources!

xSQLHAGroup, xWebSite, xADUser, xDNSServer, and xVMHyperV are some of the suggestive resource names you'll find if you install the resource kit and execute Get-DSCResource in your PowerShell terminal. They do what their names imply – configure web sites, high-availability database configurations, create users in Active Directory, etc., all with Chef-like convergence. With dsc_script, Chef users can build powerful cookbooks on top of DSC automation provided by Microsoft and the PowerShell community.

Re-using DSC configurations

While DSC itself is relatively new, ambitious users have already invested in their own libraries of DSC scripts; these are consumed very much like Chef recipes. One could integrate such a "DSC recipe" into a Chef recipe using dsc_script as follows:

dsc_script 'CompanyWiki' do    command '//infra01/configurations/wiki.ps1'    flags AuthType: 'Windows', LogArchive: '//serverlogs/wiki'  end

This will run the DSC configuration named CompanyWiki found in the wiki.ps1 script ("recipe") given by the command attribute, and pass the parameters AuthType and LogArchiveto the configuration using flags.

What's next for DSC + Chef

Chef is not yet finished with DSC:

• We've already demonstrated even tighter integration between Chef and DSC beyond dsc_script that exposes DSC purely through the Chef DSL.
• You can test out the above approach in our preview DSC community cookbook while we guide it toward its destination alongside dsc_script in core Chef Client.
• With DSC in Chef, Chefs have myriad possibilities for new and updated cookbooks — let's get cooking!

DSC accelerates our collective Chef efforts to automate all the Windows things. Now it's up to us to start building.

 

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