Commissionning of the CMS experiment and the cosmic run at four tesla

The CMS Collaboration conducted a month-long data-taking exercise known as
the Cosmic Run At Four Tesla in late 2008 in order to complete the
commissioning of the experiment for extended operation. The operational lessons
resulting from this exercise were addressed in the subsequent shutdown to
better prepare CMS for LHC beams in 2009. The cosmic data collected have been
invaluable to study the performance of the detectors, to commission the
alignment and calibration techniques, and to make several cosmic ray
measurements. The experimental setup, conditions, and principal achievements
from this data-taking exercise are described along with a review of the
preceding integration activities.