Commissioning and performance of the ATLAS Inner Detector with first beams and cosmic data

The ATLAS experiment at the CERN Large Hadron Collider (LHC) has started taking data last autumn with the inauguration of the LHC. The Inner Detector is the charged particle tracking system built on three technologies: silicon pixels, silicon micro-strips and drift tubes. The talk will review the commissioning phase of the Inner Detector in the ATLAS experimental hall, with emphasis on operational aspects, calibrations and properties of the silicon based detectors. Cosmic muon data have been used for timing the different components of the system, measuring detector performance on particle, with and without magnetic field, and cross-checking the calibration results. Cosmic ray data serves also to produce an early alignment of the real ATLAS Inner Detector even before the LHC start up, exercising the alignment procedure that will be repeated every 24h during the accelerator's running. Tracking performance after this early alignment will be presented