1. A migration method for migrating a software image installed on a source data-processing entity to a target data-processing entity, the migration method comprising: booting the target data-processing entity from a preliminary bootstrap program providing a standalone preliminary operative system, mounting the software image as a remote mass memory on the target data-processing entity, copying a primary bootstrap program of the software image onto a local mass memory of the target data-processing entity, the primary bootstrap program comprising a streaming function adapted to migrate the software image to the target data-processing entity, re-booting the target data-processing entity from the primary bootstrap program on the local mass memory of the target data-processing entity thereby loading the streaming function, and serving each request of accessing a memory block on the target data-processing entity by the streaming function, the streaming function downloading the memory block from the software image installed on the source data-processing, entity and storing the memory block into the local mass memory of the target data-processing entity in response to a lacking of the memory block in the local mass memory of the target data-processing entity, or retrieving the memory block from the local mass memory of the target data-processing entity otherwise.