As with Windows Server 2008, Windows Search is included as part of the OS and can be installed through Server Manager or PowerShell. Unfortunately it is located in a not quite intuitive place…
To enable Windows Search on Windows Server 2008 R2 you must start the Add Roles wizard and then select File Services Role, on the Role Services page you will find Windows Search:
The Role Service File Server is selected by default, so if you only want Windows Search uncheck it.
To use PowerShell to install Windows Search run:
(Remember to do ImportSystemModules first.)