Generating Keytabs
From SambaWiki
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
this should return without error.
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.