concept pull mode in category powershell

This is an excerpt from Manning's book Windows PowerShell in Action, Third Edition. Login to get full access to this book.

DSC can work in two modes: push and pull. In push mode, you’re responsible for delivering the configuration to the server. In pull mode, the target server pulls its configuration from the DSC server. We’ll explain how to set up both options and why push mode scales better to the enterprise.

The architecture of DSC in pull mode is illustrated in figure 18.4.

Figure 18.4. DSC in pull mode

Listing 18.14. Modifying the LCM to use partial configurations in pull mode

[DSCLocalConfigurationManager()] Configuration LCMpull { param ( [Parameter(Mandatory=$true)] [string[]]$ComputerName, [Parameter(Mandatory=$true)] [string]$guid, [Parameter(Mandatory=$true)] [string]$ThumbPrint ) Node $ComputerName { Settings { AllowModuleOverwrite = $True ConfigurationMode = 'ApplyAndAutoCorrect' RefreshMode = 'Pull' ConfigurationID = $guid } ConfigurationRepositoryWeb DSCHTTPS { ServerURL = 'https://W16DSC02:8080/PSDSCPullServer.svc' CertificateID = $thumbprint AllowUnsecureConnection = $false } ReportServerWeb RepSrv { ServerURL = 'http://W16DSC02:9080/PSDSCPullServer.svc' CertificateID = 'AllowUnencryptedTraffic' AllowUnsecureConnection = $true } PartialConfiguration EnvVarConfig { 1 Description = 'Sets the environmental variable' ConfigurationSource = '[ConfigurationRepositoryWeb]DSCHTTPS' RefreshMode = 'Pull' } PartialConfiguration RegConfig { 2 Description = 'Sets the registry key' ConfigurationSource = '[ConfigurationRepositoryWeb]DSCHTTPS' RefreshMode = 'Pull' } } } #$guid = New-Guid | select -ExpandProperty Guid $guid = '5827c542-20bb-487c-89cb-484cbe5f0b1f' $thumbprint=Invoke-Command -Computername W16DSC02 { Get-Childitem Cert:\LocalMachine\My | where Subject -Like 'CN=W16DSC02*' | Select-Object -ExpandProperty ThumbPrint} LCMpull -computername W16TGT01 -Guid $guid ` -Thumbprint $thumbprint -OutputPath .\MOF

18.4. DSC in pull mode

In the DSC examples you’ve seen so far, the configuration has been pushed to the target server. As you saw in section 18.3.4, push mode doesn’t scale well. In this section, we’ll cover DSC in pull mode, where the target server contacts the pull server and pulls—and then applies its configuration.