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Team Foundation Server 2015–New build agents–Installation issue

Yesterday I talked about the new agent based build system introduced in TFS 2015. I mentioned how easy it was to install them, … until you get into trouble. Today I encountered an issue when rolling out an agent on existing server. When I invoked the ConfigureAgent.ps1 script, it failed with the following message:

PS C:\build> .\ConfigureAgent.ps1
Unblocking files
The term 'Unblock-File' is not recognized as the name of a cmdlet, function, script file, or operable program. Check th
e spelling of the name, or if a path was included, verify that the path is correct and try again.
At C:\build\ConfigureAgent.ps1:12 char:52
+ Get-ChildItem -Path $currentLocation | Unblock-File <<<<  | out-null
    + CategoryInfo          : ObjectNotFound: (Unblock-File:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

The term 'Unblock-File' is not recognized as the name of a cmdlet, function, script file, or operable program. Check th
e spelling of the name, or if a path was included, verify that the path is correct and try again.
At C:\build\ConfigureAgent.ps1:13 char:67
+ Get-ChildItem -Recurse -Path $currentLocation\Agent | Unblock-File <<<<  | out-null
    + CategoryInfo          : ObjectNotFound: (Unblock-File:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

Cannot find an overload for "Combine" and the argument count: "3".
At C:\build\ConfigureAgent.ps1:15 char:43
+ $agentLocation = [System.IO.Path]::Combine <<<< ($currentLocation, 'agent', 'vsoAgent.exe')
    + CategoryInfo          : NotSpecified: (:) [], MethodException
    + FullyQualifiedErrorId : MethodCountCouldNotFindBest

Write-Error : File not found:
At C:\build\ConfigureAgent.ps1:19 char:16
+     Write-Error <<<<  "File not found: $agentLocation"
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Microsoft.PowerShell.Commands.WriteErr
   orCommand

When I invoked the $PSVersionTable.PSVersion command, it returned me the following:

Major  Minor  Build  Revision
-----  -----  -----  --------
2      0      -1     -1

To run the ConfigureAgent.ps1 script, at least version 3 of Powershell is required. Downloading a more recent version should solve the problem.

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