  It is argued that a Gibbsian formula for the space-time distribution of
microscopic trajectories of a nonequilibrium system provides a unifying
framework for recent results on the fluctuations of the entropy production. The
variable entropy production is naturally expressed as the time-reversal
symmetry breaking part of the space-time action functional. Its mean is always
positive. This is both supported by a Boltzmann type analysis by counting the
change in phase space extension corresponding to the macrostate as by various
examples of nonequilibrium models. As the Gibbsian set-up allows for
non-Markovian dynamics, we also get a local fluctuation theorem for the entropy
production in globally Markovian models. In order to study the response of the
system to perturbations, we can apply the standard Gibbs formalism.
