I believe there is an error on the documentation "Samba AD DC HOWTO":
In section Kerberos there is a proposen command:
ln -sf /usr/local/samba/share/setup/krb5.conf /etc/krb5.conf
That should be
ln -sf /usr/local/samba/private/krb5.conf /etc/krb5.conf
as the content of the other krb5.conf is not adapted für the current environment.
You're right. I fixed the command. Thanks.