The local repository is needed to download the metadata and artifacts to. This directory can safely be removed from time to time, but already resolved artifacts might have to be downloaded again. It can point to an already existing Maven repository or be a separate one. Define the repositories to connect to.
User/Password for deployment of artifacts can be overwriten on Job level. Note: because of this bug https://issues.sonatype.org/browse/NEXUS-3776 one should use at least Nexus 1.8.*