  We provide a rigorous derivation of the compressible Reynolds system as a
singular limit of the compressible (barotropic) Navier-Stokes system on a thin
domain. In particular, the existence of solutions to the Navier-Stokes system
with non-homogeneous boundary conditions is shown that may be of independent
interest. Our approach is based on new a priori bounds available for the
pressure law of hard sphere type. Finally, uniqueness for the limit problem is
established in the 1D case.
