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TFS Build Agent doesn’t pick up all capabilities

Once a TFS build agent is configured on a build server it should scan the server for all capabilities and add them to a list. These capabilities can then be linked to demands to select an appropriate agent for your specific build script.

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However at one client we noticed that the list of capabilities for all agents turned out rather empty whereas a lot of components were in fact installed on the server.

Inside the agent logs we found the following error message:

[2017-05-03 09:06:01Z INFO ProcessInvoker] Process started with process id 2828, waiting for process exit.

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR: . : File D:\Builds\dev-agent-3\bin\powershell\Add-Capabilities.ps1 cannot be loaded. The file D:\Builds\dev-agent-3\bin

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR: \powershell\Add-Capabilities.ps1 is not digitally signed. You cannot run this script on the current system. For more in

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR: formation about running scripts and setting execution policy, see about_Execution_Policies at http://go.microsoft.com/f

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR: wlink/?LinkID=135170.

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR: At line:1 char:3

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR: + . 'D:\Builds\dev-agent-3\bin\powershell\Add-Capabilities.ps1'

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR: +   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR:     + CategoryInfo          : SecurityError: (:) [], PSSecurityException

[2017-05-03 09:06:03Z INFO PowerShellCapabilitiesProvider] STDERR:     + FullyQualifiedErrorId : UnauthorizedAccess

[2017-05-03 09:06:03Z INFO ProcessInvoker] Finished process with exit code 1, and elapsed time 00:00:01.2248303.

On this server a group policy is applied that prevents the execution of unsiged Powershell scripts. As the agent is using Powershell to scan a system for capabilities it failed silenty behind the scenes.

The solution was to ask the server team to sign all scripts for us.

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