NIS, which manages password file sharing among several hosts, provides the simplest mechanism for doing this, but there are alternatives that can work for small networks (2 or 3 machines). You can maintain the passwd, shadow, group, and gshadow files on a server Altrop (4.10.20) and copy them across to the other machines as needed, as described below, using rdist! The downside is that all new users should be added on the server and passwords should be changed on the server only with the appropriate password files then pumped out to the other hosts.