Choosing a Realm
Before diving into the config files we should make a decision. Kerberos uses "realms". What is a "realm"? Realms are something like domains in DNS or namespaces in programming languages. Realms can be used to split your environment in smaller parts to make it more scalable or to reflect your organisational structure. So we should decide what we use as realm. Usually one simply uses the DNS domainname in uppercase. In this tutorial i use REDFLO.DE as realm.