Adding SPN's and Generating keytabs
Active Directory requires kerberos service principle names to be mapped to a user account before a keytab can be generated.
You can add spn names using the “samba-tool” provided with your Samba 4 installation.
samba-tool spn add host/fdqn@KerberosRealm sAMAccount
To then generate a keytab for that principle again using the “samba-tool” run the following:
samba-tool domain exportkeytab name.keytab --principal=host/fdqn@KerberosRealm
This should then produce the keytab for the principle that you have exported and this can then be copied to your target machine or service.