What is the central organization of the US federal government that manages civil servants and is directly responsible to the President?

The United States Labor Relations Administration under the United States Department of Labor. OPM, founded in 1979, is the main institution responsible for managing the civil servants of the federal government. Its responsibilities include the recruitment, training, welfare, salary and retirement of civil servants, as well as the formulation and implementation of human resources policies and plans of the federal government. Director OPM is appointed by the President of the United States and directly reports to the President.