Originally posted by Sutha:

The Permitted list.txt (also known as Whitelist) allows you to limit the access to your server to only the players added into this file.

Once you have gotten your STEAM_64_ID insert it into the text box, then click to Save Changes.

EDIT: Wait, I just re-read the question. Are you asking to keep only players you know from entering the server? Or if you can do, say; Permanent character type binding to the server? Apologies.

to be clear, I'm trying to make sure my friends when they enter my server, those characters can only be used by that server.

In the past, one of my buddies entered my server, created a character, then made his own personal game and cheated his way with legendary weapons and using methods to gain insane amount of materials. In around 2-3 hours or 1 day or so, he made buildings freak'n huge like a baseball stadium. All because is character had access to his personal game and could create, dupe his away around items. This is what I`m trying to prevent.

Other games have this type as characters and items are kept on the server and not the client to prevent idiocy like this. In terms of duping items and cheating, its too easy in this game.