A realm is where the kerberos database is stored. The realm lives on one computer (KDC) and can have read-only slave servers (kinda’ like a cluster). Each realm will have a listing in the following files
/private/var/db/krb5kdc/
.k5.FQDN.OF.REALM (secret key)
kdc.conf (configuration file for the KDC)
kadm5.acl (access control list for KDC)