  We report the discovery of a linear relationship between the root-mean-square
(rms) variability amplitude and the mean flux in the accreting white dwarf
binary system MV Lyrae. Our lightcurve, obtained with the Kepler satellite,
spans 633 days with quasi-continuous 58.8 second cadence resolution. We show,
for the first time, how this cataclysmic variable displays linear rms-flux
relations similar to those observed in many other black hole binaries, neutron
star binaries and Active Galactic Nuclei. The phenomenological similarity
between the rms-flux relation observed here and in other X-ray binaries
suggests a common physical origin for the broad-band variability, independent
of source type, mass or size of the compact accretor. Furthermore, we infer the
viscosity parameter, alpha, and disk scale height, H/R, using two independent
methods. In both cases, both values are found to be uncomfortably high to be
accommodated by the disk instability model.
