In this chapter, we will cover the following recipes:
Desired State Configuration (DSC) is management platform within Windows Server and is implemented with Windows PowerShell. DSC enables you to define a computer's desired state declaratively and have PowerShell ensure the computer is configured accordingly and remains so. This is simpler than writing complex scripts to configure a given computer. Microsoft added DSC with PowerShell and delivered improvements V5 and V/5.1 and Server 2016.
With DSC, you define a configuration that describes the details of how a given node (computer) is to be configured. The configuration defines a series of resources to be invoked on the node and how these resources should be configured. A DSC resource is PowerShell code and executable that knows to configure a given object residing on a node. Resources primarily exist as PowerShell modules and you need them both on the computer on which you author DSC configurations and on the target node.
For example, you could define a node and specify that the...
Windows Server 2016 comes with a limited set of built-in DSC resources. In this recipe, you explore the built-in DSC resources and then write and deploy a simple configuration to a single node. The recipe also examines changes in configuration.
In this recipe, you examine the Windows Server 2016 built-in resources and use these to create and compile a configuration statement on server SRV1. You use this configuration statement to then deploy the Web-Server feature on a second server, SRV2.
This recipe relies on two files being created and shared from DC1. The two files are Index.Htm, and Page2.Htm. These two files are created and shared as \\DC1\ReskitApp. The first file, Index.HTM contains the following:
<!DOCTYPE html> <html> <head><title>Main Page - ReskitApp Application</title></head> <body><p><center> <b>HOME PAGE FOR RESKITAPP APPLICATION</b></p> This is the root...
As with functions, you can create configuration blocks with parameters. These enable you to produce different MOF files by varying the parameter values used when you execute the configuration.
For example, suppose you wanted to add a feature to a node. You could create a specific configuration where you hard code the feature name and the node name. This is not dissimilar to how you copied specific files from DC1 to SRV1 in the use DSC and built-in resources recipe.
Alternatively, you could create a configuration that takes the node name and the service name as parameters and when you run the configuration, PowerShell creates a MOF file that adds the specified service to the specified node. This recipe demonstrates that approach.
One challenge this approach throws up is that, by default, you can only send a single MOF file to a given node. Thus, if you used the earlier recipe and copied files to SRV2, attempting to send a second MOF file to the system results...
A DSC resource is a specially created PowerShell module that enables DSC to configure various aspects of a node. The WindowsFeature DSC resource, for example, enables you to ensure that a particular node of a particular Windows feature installed. You could also specify that a particular Windows feature should not be present.
As you have seen in this chapter so far, Windows comes with a few DSC resources built in. But these do not provide broad coverage. For example, you can use the built-in File resource to copy the source files for a small web application onto a new server. But the built-in resources do not allow you to specify the application's settings (what the application name is, which application pool it runs in, and so on) which is where add-on DSC resources come in.
The community, which includes various Microsoft teams, has been busy since the release of DSC with PowerShell V4 and has created a large range of additional resources. These resources...
In the Finding and installing DSC resources recipe, you downloaded a module, xWebAdministration, which contains a number of DSC resources. In this recipe, you use the resources in this module to create an IIS web application. You create and run this recipe from SRV1 to configure a web application on SRV2. You obtain the source files for the web application from DC1.
With this recipe, you configure IIS on SRV2 to support a simple web application—a similar application. To test this recipe, you need two source files, which you store on the ReskitApp share on your DC1 computer. The first, Index.Htm contains the following:
<!DOCTYPE html> <html> <head><meta charset="utf-8" /> <title>Main Page of The ReskitApp Application</title> </head> <body></p> <br> <center> <b>Home Page for ReskitApp Application</b></p> The home page of the ReskitApp application pushed...
The LCM is a key component of DSC that initially shipped within PowerShell V4. LCM is a Windows service that runs on each DSC target node and is responsible for receiving configuration information and ensuring the node is configured in the desired state (and remains that way).
The LCM has two mechanisms for desired state delivery: push and pull. The earlier recipes in this chapter demonstrate the push model: you create a configuration and its related MOF file on one node, and push that configuration to another node. In the pull model, you configure the node with details of where and how to find a pull server. Once configured, a node can pull configurations from the configured pull server.
With this recipe, which you run on SRV2, you configure the LCM based on PowerShell V5/5.1. PowerShell V4 used a different approach to configuring the LCM. In this recipe, you configure the LCM on SRV2 and set up SRV2 to use SRV1 as an SMB pull server. You setup SRV1...
There are two different types of DSC pull server you implement: SMB-based and web-based. The SMB-based pull server approach is most useful on a private routable network, one where all nodes can reach the centralized configuration and resource pull server shares. For high availability, you could set up an SMB pull server on a scale out file server.
In DSC, MOF files are used to communicate the desired state to a node. The LCM on that node, in effect, does anything the MOF file says. MOF files are ,at rest, just plain text documents and are not encrypted or signed. If your private network is secure, then the SMB pull server is easier to set up and configure. If security is an issue, consider using the web server pull server approach and configure it with HTTPS.
In the previous recipe, Configuring Local Configuration Manager, you configured a node, SRV2 to pull configurations from a DSC pull server. In this recipe, you configure another node, SRV1, to be the pull...
Deploying a DSC web-based pull server is more complex than deploying an SMB pull server. The SMB-based pull server is simple: just create a couple of shares and place the relevant files on that share. The web server approach requires you to also load IIS, install the DSC service, and configure the service, as well as placing the MOF files, resources, and any relevant checksums on the web server. Of course, in both cases, you need to configure each node's LCM.
You deploy a web based pull server to provide a pull client with both resources and configuration MOF files. Unlike an SMB-based pull server, a web-based pull server also provides reporting capabilities enabling a pull client to report status back to the reporting server. Reporting is not available using an SMB-based pull server.
To simplify the creation of a web-based DSC pull server, you can use the xPSDesiredStateConfiguration module DSC resource. You download this resource from PSGallery. This...
PowerShell V5 introduced a new feature with DSC: partial configurations. A partial configuration, as the name suggests, is part of the configuration you wish to see applied to a given node.
Partial configurations allow you to share the configuration of a node between multiple teams. For example, you might want the central IT team to define the basic configuration of a node. Another team could be responsible for deploying a web application to that same node. With PowerShell 4, you would have needed to put all the configuration components into a single configuration document/MOF file and deploy that to the node.
To support partial configurations, you must configure each node's LCM to define the partial configurations, and how they are to be deployed. Each partial configuration can be either pushed or pulled. Thus, you can deploy partial configurations that direct the node to pull the basic host configuration for an IT central configuration server and to pull...
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