Operational experience and performance of the CMS pixel detector during the first LHC beams

The CMS pixel detector is a complex system consisting of 66 M pixels of $100x150~mu m$ size with the main goal of high resolution reconstruction of charged particle tracks. It took almost 10 years of design, construction and commissioning before operation with LHC beams. After the installation in July 2008, the pixel detector was commissioned and calibrated with cosmic muons and the first proton collisions. This paper describes the operational experience, the calibration, and the performance of the pixel detector.