Determines which Unix users on the client are trusted by the server. Three options are available :

Everyone
  All client users will be treated the same by the server
Everyone except root
  The `root` user on the client is treated as the untrusted user by the server, but all other users are trusted.
Nobody
  All users on the client are treated as the untrusted user. This option is best used when exporting to a system that you do not control (such as a single-user PC), or when exporting to everyone.