When trying to install .NET 3.5 or another Windows feature on Microsoft Windows Server 2012, you may get this error:
Do you need to specify an alternate source path? One or more installation selections are missing source files on the destination server. The server will try to get missing source files from Windows Update, or from a location that is specified by Group Policy. You can also click the “Specify an alternate source path” link to provide a valid location for the source files.
The Do you need to specify an alternate source path? error is caused by the feature installation files missing from Server 2012. This is a new security feature called Features on Demand, which removes the installation files for features that are not in use. This reduces the surface of attack on the Windows machine and the requirement for many updates. Typically Windows feature files are available by default, but for some reason the files for the .NET framework 3.5 feature are not.
To fix the Do you need to specify an alternate source path? error, you have three options:
- Click the Specify an alternate source path link at the bottom of the window and follow the instructions on the page to specify an alternate source path for the feature installation files
- Use DISM commands to install the feature, specifying the source path for the files. (Here’s the DISM command to install the .NET Framework 3.5 feature on Server 12 or Windows 8)
- There’s also a PowerShell option for installing features and specifying source locations for installation media too