  We consider the time evolution of two entropy-like quantities, the
holographic entanglement entropy and causal holographic information, in a model
of holographic thermalization dual to the gravitational collapse of a thin
planar shell. Unlike earlier calculations valid in different limits, we perform
a full treatment of the dynamics of the system, varying both the shell's
equation of state and initial position. In all cases considered, we find that
between an early period related to the acceleration of the shell and a late
epoch of saturation towards the thermal limit, the entanglement entropy
exhibits universal linear growth in time in accordance with the prediction of
Liu and Suh. As intermediate steps of our analysis, we explicitly construct a
coordinate system continuous at the location of an infinitely thin shell and
derive matching conditions for geodesics and extremal surfaces traversing this
region.
