dsc_resource Resource

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To suggest a change, edit the dsc_resource.rb file and submit a pull request to the Chef Infra Client repository.

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Windows PowerShell is a task-based command-line shell and scripting language developed by Microsoft. Windows PowerShell uses a document-oriented approach for managing Windows-based machines, similar to the approach that’s 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 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.

Using the dsc_resource has the following requirements:

Windows Management Framework (WMF) 5.0 (or higher)
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 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.

Warning

New in Chef Infra Client 12.2.

Syntax

A dsc_resource resource block allows DSC resources 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_version      String
  reboot_action       Symbol # default value: :nothing
  timeout             Integer
  action              Symbol # defaults to :run if not specified
end

where:

dsc_resource is the resource.
name is the name given to the resource block.
action identifies which steps Chef Infra Client will take to bring the node into the desired state.
module_version, reboot_action, and timeout are the properties available to this resource.

Actions

The dsc_resource resource has the following actions:

:nothing: This resource block doesn’t act unless notified by another resource to take action. Once notified, this resource block either runs immediately or is queued up to run at the end of a Chef Infra Client run.
:run: (default)

Properties

The dsc_resource resource has the following properties:

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.

module_version

Ruby Type: String

The version number of the module to use. PowerShell 5.0.10018.0 (or higher) supports having multiple versions of a module installed. This should be specified along with the module_name property.

New in Chef Client 12.21

property

Ruby Type: String

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	PowerShell
`:array`	`Object[]`
`Chef::Util::Powershell:PSCredential`	`PSCredential`
`False`	`bool($false)`
`Fixnum`	`Integer`
`Float`	`Double`
`Hash`	`Hashtable`
`True`	`bool($true)`

These are converted into the corresponding Windows PowerShell type during a Chef Infra Client run.

reboot_action

Ruby Type: Symbol | Default Value: :nothing
Allowed Values: :nothing, :reboot_now, :request_reboot

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.

New in Chef Client 12.6

resource

Ruby Type: Symbol

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 unpack archive (.zip) files.
`:environment`	Use to manage system environment variables.
`:file`	Use to manage files and directories.
`:group`	Use to manage local groups.
`:log`	Use to log configuration messages.
`:package`	Use to install and manage packages.
`:registry`	Use to manage registry keys and registry key values.
`:script`	Use to run PowerShell script blocks.
`:service`	Use to manage services.
`:user`	Use to manage local user accounts.
`:windowsfeature`	Use to add or remove Windows features and roles.
`:windowsoptionalfeature`	Use to configure Microsoft Windows optional features.
`:windowsprocess`	Use 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 Chef Infra Client, the corresponding values for the resource attribute would be: :xADDomain, :xADDomainController, and xADUser.

timeout

Ruby Type: Integer

The amount of time (in seconds) a command is to wait before timing out.

Common Resource Functionality

Chef resources include common properties, notifications, and resource guards.

Common Properties

The following properties are common to every resource:

compile_time

Ruby Type: true, false | Default Value: false

Control the phase during which the resource is run on the node. Set to true to run while the resource collection is being built (the compile phase). Set to false to run while Chef Infra Client is configuring the node (the converge phase).

ignore_failure

Ruby Type: true, false, :quiet | Default Value: false

Continue running a recipe if a resource fails for any reason. :quiet won’t display the full stack trace and the recipe will continue to run if a resource fails.

retries

Ruby Type: Integer | Default Value: 0

The number of attempts to catch exceptions and retry the resource.

retry_delay

Ruby Type: Integer | Default Value: 2

The delay in seconds between retry attempts.

sensitive

Ruby Type: true, false | Default Value: false

Ensure that sensitive resource data isn’t logged by Chef Infra Client.

Notifications

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 notify more than one resource; use a notifies statement for each resource to be notified.

If the referenced resource doesn’t exist, an error is raised. In contrast, subscribes won’t fail if the source resource isn’t found.

A timer specifies the point during a Chef Infra 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 end of a Chef Infra Client run.
:immediate, :immediately: Specifies that a notification should be run immediately, for each resource notified.

The syntax for notifies is:

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

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.

Note that subscribes doesn’t apply the specified action to the resource that it listens to - for example:

file '/etc/nginx/ssl/example.crt' do
  mode '0600'
  owner 'root'
end

service 'nginx' do
  subscribes :reload, 'file[/etc/nginx/ssl/example.crt]', :immediately
end

In this case the subscribes property reloads the nginx service whenever its certificate file, located under /etc/nginx/ssl/example.crt, is updated. subscribes doesn’t make any changes to the certificate file itself, it merely listens for a change to the file, and executes the :reload action for its resource (in this example nginx) when a change is detected.

If the other resource doesn’t exist, the subscription won’t raise an error. Contrast this with the stricter semantics of notifies, which will raise an error if the other resource doesn’t exist.

A timer specifies the point during a Chef Infra 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 end of a Chef Infra Client run.
:immediate, :immediately: Specifies that a notification should be run immediately, for each resource notified.

The syntax for subscribes is:

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

Guards

A guard property can be used to evaluate the state of a node during the execution phase of a Chef Infra Client run. Based on the results of this evaluation, a guard property is then used to tell Chef Infra Client if it should continue executing a resource. A guard property accepts either a string value or a Ruby block value:

A string is executed as a shell command. If the command returns 0, the guard is applied. If the command returns any other value, then the guard property isn’t applied. String guards in a powershell_script run Windows PowerShell commands and may return true in addition to 0.
A block is executed as Ruby code that must return either true or false. If the block returns true, the guard property is applied. If the block returns false, the guard property isn’t applied.

A guard property is useful for ensuring that a resource is idempotent by allowing that resource to test for the desired state as it’s being executed, and then if the desired state is present, for Chef Infra Client to do nothing.

Properties

The following properties can be used to define a guard that’s evaluated during the execution phase of a Chef Infra Client run:

not_if: Prevent a resource from executing when the condition returns true.
only_if: Allow a resource to execute only if the condition returns true.

Examples

The following examples demonstrate various approaches for using the dsc_resource resource in recipes:

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 and register a windows service

The following example creates a windows service, defines it’s execution path, and prevents windows from starting the service in case the executable is not at the defined location:

dsc_resource 'NAME' do
  resource :service
  property :name, 'NAME'
  property :startuptype, 'Disabled'
  property :path, 'D:\\Sites\\Site_name\file_to_run.exe'
  property :ensure, 'Present'
  property :state, 'Stopped'
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

Example to show usage of module properties

dsc_resource 'test-cluster' do
  resource :xCluster
  module_name 'xFailOverCluster'
  module_version '1.6.0.0'
  property :name, 'TestCluster'
  property :staticipaddress, '10.0.0.3'
  property :domainadministratorcredential, ps_credential('abcd')
end