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.
Warning
Using the dsc_resource has the following requirements:
Windows Management Framework (WMF) 5.0 February Preview (or higher), which includes Windows PowerShell 5.0.10018.0 (or higher).
The RefreshMode configuration setting in the Local Configuration Manager must be set to Disabled.
NOTE: Starting with the chef-client 12.6 release, this requirement applies only for versions of Windows PowerShell earlier than 5.0.10586.0. The latest version of Windows Management Framework (WMF) 5 has relaxed the limitation that prevented the chef-client from running in non-disabled refresh mode.
The dsc_script resource may not be used in the same run-list with the dsc_resource. This is because the dsc_script resource requires that RefreshMode in the Local Configuration Manager be set to Push, whereas the dsc_resource resource requires it to be set to Disabled.
NOTE: Starting with the chef-client 12.6 release, this requirement applies only for versions of Windows PowerShell earlier than 5.0.10586.0. The latest version of Windows Management Framework (WMF) 5 has relaxed the limitation that prevented the chef-client from running in non-disabled refresh mode, which allows the Local Configuration Manager to be set to Push.
The dsc_resource resource can only use binary- or script-based resources. Composite DSC resources may not be used.
This is because composite resources aren’t “real” resources from the perspective of the the Local Configuration Manager (LCM). Composite resources are used by the “configuration” keyword from the PSDesiredStateConfiguration module, and then evaluated in that context. When using DSC to create the configuration document (the Managed Object Framework (MOF) file) from the configuration command, the composite resource is evaluated. Any individual resources from that composite resource are written into the Managed Object Framework (MOF) document. As far as the Local Configuration Manager (LCM) is concerned, there is no such thing as a composite resource. Unless that changes, the dsc_resource resource and/or Invoke-DscResource command cannot directly use them.
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