Linac4 has been commissioned with a temporary source until the energy of 12 MeV. The dynamics in the LEBT, in the RFQ and in the chopper line have been verified, as well as the acceleration to 12 MeV with the first DTL tank. Future plans foresee stages of commissioning at the energy of 50, 100 and finally 160 MeV interlaced with periods of installation and followed by a year-long reliability run. In this talk we will present the status of the linac4 beam commissioning, the status of readiness of the remaining accelerating structures as well as the path to the final source. The possibility of delivering to the PSB a 50 MeV proton beam from Linac4 will be discussed together with its impact on the overall schedule and the achievable beam characteristics.