Commissioning, operation and performance of the CMS drift tube chambers

The CMS muon spectrometer, designed to trigger, identify, reconstruct and measure muons with high efficiency and accuracy, is equipped with Drift Tube (DT) chambers in the barrel region. The DT system has been fully commissioned using cosmic muons with and without magnetic field, and during months of cosmic data taking has provided millions of triggers to the rest of the CMS detector. This contribution describes the challenges in the operation of the DT system, including reconstruction performance, and the result of the analysis of the collected cosmic data.