portmap - A daemon to manage RPC connections.

The portmapper is a network daemon used to manage connections to
RPC services. Daemons that offer RPC services (such as the daemons
for NFS) tell the portmapper on what port they listen. Unlike the
services registered with the xinetd, RPC network port numbers
may change each time the system is booted.

The portmapper is required to use NFS or other RPC services.