  In this paper we study formal moduli for wildly ramified Galois covering. We
prove a local-global principle. We then focus on the infinitesimal deformations
of the Z/pZ-covers. We explicitly compute a deformation of an automorphism of
order p which implies a universal obstruction for p>2. By deforming
Artin-Schreier equations we obtain a lower bound on the dimension of the local
versal deformation ring. At last, by comparing the global versal deformation
ring to the complete local ring in a point of a moduli space, we determine the
dimensions of the global and local versal deformation ring.
