What is portmap in Linux?

Answer 1

Portmap is a server that converts RPC program numbers into DARPA protocol port numbers. It must be running in order to make RPC calls.

The port mapper (rpc.portmap or just portmap, or rpcbind) is an Open Network Computing Remote Procedure Call (ONC RPC) service that runs on network nodes that provide other ONC RPC services.

The port mapper service always uses TCP or UDP port 111; a fixed port is required for it, as a client would not be able to get the port number for the port mapper service from the port mapper itself.

The port mapper must be started before any other RPC servers are started.

The port mapper service first appeared in SunOS 2.0.