No password Kerberos authentication (gssapi) with Samba Active Directory

After you have setup your workstation and server to join your samba4 Active Directory DC, you can setup Kerberos authentication to ssh into the server without needing to retype your password (single sign-in)

Just add these lines to the /etc/ssh/sshd_config on the server

KerberosAuthentication yes
GSSAPIAuthentication yes
GSSAPICleanupCredentials yes
UsePAM no

And add these lines to the /etc/ssh/ssh_config on the client

 GSSAPIAuthentication yes
 GSSAPIDelegateCredentials yes

Credential delegation is the magic that passes your password to the server. Voila!