The CMS tracker

The tracker for the CMS detector at the LHC experiment will provide the possibility to both tag and reconstruct in detail $b$-jets and $b$-hadrons inside those jets. 15.148 silicon strip detectors and a pixel vertexing system allow secondary vertices to be found over the full CMS acceptance. This is necessary to study $B$-hadron physics including CP-violation, $B_s$ oscillations and rare $B$-decays right after the start of the experiment. After a more general description of the detector layout, expected results in terms of reconstruction capability with a special attention to vertexing and heavy flavor tagging are given.