We discuss the physical interpretation of the Lagrange multipliers appearing in the information-theoretical description of nonequilibrium steady states characterized by a heat flux or a viscous pressure. Some of the multipliers have a classical counterpart (temperature, pressure, chemical potential, ...) but their equations of state are modified by the fluxes, whereas some others, those which are related to nonequilibrium constraints, do not have an analogous in the equilibrium theory. We give definite results for the Lagrange multipliers, the partition function and the nonequilibrium entropy in some simple simple situations which provide explicit illustrations of their dependence on the fluxes. We end with some comments about the experimental verification of this dependence for the Lagrange multipliers conjugated to the internal energy.