dsc_resource

Windows PowerShell is a task-based command-line shell and scripting language developed by Microsoft. Windows PowerShell uses a document-oriented approach for managing Microsoft Windows-based machines, similar to the approach that is used for managing UNIX- and Linux-based machines. Windows PowerShell is a tool-agnostic platform that supports using Chef for configuration management.

Desired State Configuration (DSC) is a feature of Windows PowerShell that provides a set of language extensions, cmdlets, and resources that can be used to declaratively configure software. DSC is similar to Chef, in that both tools are idempotent, take similar approaches to the concept of resources, describe the configuration of a system, and then take the steps required to do that configuration. The most important difference between Chef and DSC is that Chef uses Ruby and DSC is exposed as configuration data from within Windows PowerShell.

The dsc_resource resource allows any DSC resource to be used in a Chef recipe, as well as any custom resources that have been added to your Windows PowerShell environment. Microsoft frequently adds new resources to the DSC resource collection.

Syntax

A dsc_resource resource block allows DSC resourcs to be used in a Chef recipe. For example, the DSC Archive resource:

Archive ExampleArchive {
  Ensure = "Present"
  Path = "C:\Users\Public\Documents\example.zip"
  Destination = "C:\Users\Public\Documents\ExtractionPath"
}

and then the same dsc_resource with Chef:

dsc_resource 'example' do
   resource :archive
   property :ensure, 'Present'
   property :path, "C:\Users\Public\Documents\example.zip"
   property :destination, "C:\Users\Public\Documents\ExtractionPath"
 end

The full syntax for all of the properties that are available to the dsc_resource resource is:

dsc_resource 'name' do
  module_name                String
  notifies                   # see description
  property                   Symbol
  resource                   String
  subscribes                 # see description
end

where

• dsc_resource is the resource
• name is the name of the resource block
• property is zero (or more) properties in the DSC resource, where each property is entered on a separate line, :dsc_property_name is the case-insensitive name of that property, and "property_value" is a Ruby value to be applied by the chef-client
• module_name, property, and resource are properties of this resource, with the Ruby type shown. See “Properties” section below for more information about all of the properties that may be used with this resource.

Actions

This resource has the following actions:

:nothing

Default.

Define this resource block to do nothing until notified by another resource to take action. When this resource is notified, this resource block is either run immediately or it is queued up to be run at the end of the chef-client run.

:reboot_action

Use to request an immediate reboot or to queue a reboot using the :reboot_now (immediate reboot) or :request_reboot (queued reboot) actions built into the reboot resource.

Properties

This resource has the following properties:

ignore_failure

Ruby Types: TrueClass, FalseClass

Continue running a recipe if a resource fails for any reason. Default value: false.

module_name

Ruby Type: String

The name of the module from which a DSC resource originates. If this property is not specified, it will be inferred.

notifies

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may notify another resource to take action when its state changes. Specify a 'resource[name]', the :action that resource should take, and then the :timer for that action. A resource may notifiy more than one resource; use a notifies statement for each resource to be notified.

A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:

:before

Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.

:delayed

Default. Specifies that a notification should be queued up, and then executed at the very end of the chef-client run.

:immediate, :immediately

Specifies that a notification should be run immediately, per resource notified.

The syntax for notifies is:

notifies :action, 'resource[name]', :timer

property

Ruby Type: Symbol

A property from a Desired State Configuration (DSC) resource. Use this property multiple times, one for each property in the Desired State Configuration (DSC) resource. The format for this property must follow property :dsc_property_name, "property_value" for each DSC property added to the resource block.

The :dsc_property_name must be a symbol.

Use the following Ruby types to define property_value:

Ruby	Windows PowerShell
Array	Object[]
Chef::Util::Powershell:PSCredential	PSCredential
FalseClass	bool($false)
Fixnum	Integer
Float	Double
Hash	Hashtable
TrueClass	bool($true)

These are converted into the corresponding Windows PowerShell type during the chef-client run.

resource

Ruby Type: String

The name of the DSC resource. This value is case-insensitive and must be a symbol that matches the name of the DSC resource.

For built-in DSC resources, use the following values:

Value	Description
:archive	Use to to unpack archive (.zip) files.
:environment	Use to to manage system environment variables.
:file	Use to to manage files and directories.
:group	Use to to manage local groups.
:log	Use to to log configuration messages.
:package	Use to to install and manage packages.
:registry	Use to to manage registry keys and registry key values.
:script	Use to to run Powershell script blocks.
:service	Use to to manage services.
:user	Use to to manage local user accounts.
:windowsfeature	Use to to add or remove Windows features and roles.
:windowsoptionalfeature	Use to configure Microsoft Windows optional features.
:windowsprocess	Use to to configure Windows processes.

Any DSC resource may be used in a Chef recipe. For example, the DSC Resource Kit contains resources for configuring Active Directory components, such as xADDomain, xADDomainController, and xADUser. Assuming that these resources are available to the chef-client, the corresponding values for the resource attribute would be: :xADDomain, :xADDomainController, and xADUser.

retries

Ruby Type: Integer

The number of times to catch exceptions and retry the resource. Default value: 0.

retry_delay

Ruby Type: Integer

The retry delay (in seconds). Default value: 2.

subscribes

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may listen to another resource, and then take action if the state of the resource being listened to changes. Specify a 'resource[name]', the :action to be taken, and then the :timer for that action.

A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:

:before

Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.

:delayed

Default. Specifies that a notification should be queued up, and then executed at the very end of the chef-client run.

:immediate, :immediately

Specifies that a notification should be run immediately, per resource notified.

The syntax for subscribes is:

subscribes :action, 'resource[name]', :timer

Examples

The following examples demonstrate various approaches for using resources in recipes. If you want to see examples of how Chef uses resources in recipes, take a closer look at the cookbooks that Chef authors and maintains: https://github.com/chef-cookbooks.

Open a Zip file

dsc_resource 'example' do
   resource :archive
   property :ensure, 'Present'
   property :path, 'C:\Users\Public\Documents\example.zip'
   property :destination, 'C:\Users\Public\Documents\ExtractionPath'
 end

Manage users and groups

dsc_resource 'demogroupadd' do
  resource :group
  property :groupname, 'demo1'
  property :ensure, 'present'
end

dsc_resource 'useradd' do
  resource :user
  property :username, 'Foobar1'
  property :fullname, 'Foobar1'
  property :password, ps_credential('P@assword!')
  property :ensure, 'present'
end

dsc_resource 'AddFoobar1ToUsers' do
  resource :Group
  property :GroupName, 'demo1'
  property :MembersToInclude, ['Foobar1']
end

Create a test message queue

The following example creates a file on a node (based on one that is located in a cookbook), unpacks the MessageQueue.zip Windows PowerShell module, and then uses the dsc_resource to ensure that Message Queuing (MSMQ) sub-features are installed, a test queue is created, and that permissions are set on the test queue:

cookbook_file 'cMessageQueue.zip' do
  path "#{Chef::Config[:file_cache_path]}\\MessageQueue.zip"
  action :create_if_missing
end

windows_zipfile "#{ENV['PROGRAMW6432']}\\WindowsPowerShell\\Modules" do
  source "#{Chef::Config[:file_cache_path]}\\MessageQueue.zip"
  action :unzip
end

dsc_resource 'install-sub-features' do
  resource :windowsfeature
  property :ensure, 'Present'
  property :name, 'msmq'
  property :IncludeAllSubFeature, true
end

dsc_resource 'create-test-queue' do
  resource :cPrivateMsmqQueue
  property :ensure, 'Present'
  property :name, 'Test_Queue'
end

dsc_resource 'set-permissions' do
  resource :cPrivateMsmqQueuePermissions
  property :ensure, 'Present'
  property :name, 'Test_Queue_Permissions'
  property :QueueNames, 'Test_Queue'
  property :ReadUsers, node['msmq']['read_user']
end