Windows Classroom Series – 28/Oct/2020

Powershell DSC (Desired State Configuration)

• Powershell DSC helps ensuring resources are correctly configured. Powershell DSC is a declarative way of configuring resources.
• Powershell DSC is released as a feature of Powershell.
• Powershell DSC as a set of Powershell Language Extensions
• A Sample DSC would look like

configuration TemporaryConfiguration 
{
   File TempFile 
   {
         Ensure = 'Present'
         Type = 'File'
         DestinationPath = 'C:\temp.txt'
         Contents = 'This is sample DSC Configuration'
   }
}

• In the above case we are expressing the desired state rather than writing how to create a file.

High level Overview

• DSC has several steps that can be grouped into three phases
  • Authoring Phase:
    • We begin with writing DSC Configuration script in Powershell.
    • Generate a MOF (Managed Object Format) for the configuration
  • Staging Phase
    • Deploying the MOF into server which can happen in two ways
      • PUSH
      • PULL
  • Execution Phase
    • In this MOF file will be executed by Local Configuration Manager.

Push based Model

Pull Based Model

Hello-World Configuration

• Create a PS1 file with the Sample DSC Configuration as shown below
• Now, Generate MOF file by executing the powershell file
• Lets look into contents of mof

/*
@TargetNode='localhost'
@GeneratedBy=qtkha
@GenerationDate=10/28/2020 17:55:51
@GenerationHost=DESKTOP-45IKD7M
*/

instance of MSFT_LogResource as $MSFT_LogResource1ref
{
SourceInfo = "D:\\khajaclassroom\\windows\\powershell\\dsc\\hello-dsc\\hellodsc.ps1::8::5::Log";
 ModuleName = "PsDesiredStateConfiguration";
 ResourceID = "[Log]MyMessage";
 Message = "Hello, Welcome to the World of DSC";

ModuleVersion = "1.0";

 ConfigurationName = "HelloDsc";

};
instance of OMI_ConfigurationDocument


                    {
 Version="2.0.0";
 

                        MinimumCompatibleVersion = "1.0.0";
 

                        CompatibleVersionAdditionalProperties= {"Omi_BaseResource:ConfigurationName"};
 

                        Author="qtkha";
 

                        GenerationDate="10/28/2020 17:55:51";
 

                        GenerationHost="DESKTOP-45IKD7M";
 

                        Name="HelloDsc";


                    };

• Now lets execute the MOF file by using the cmd-let Start-DSCConfiguration

Start-DscConfiguration -Path .\HelloDSC -Wait -Verbose

• Powershell works very well in a domain controller. So the lab setup would be as shown below
• Next Steps:
  • Configuration Data
  • Configuration
  • DSC Resources & Modules
  • Powershell DSC to install web servers