anchor.diff:  
           exec =
             ''
  -            ${pkgs.openssh}/sbin/sshd -h /etc/ssh/ssh_host_dsa_key \
  +            ${pkgs.openssh}/sbin/sshd -h /etc/ssh/ssh_host_${hktn}_key \
                 -f ${pkgs.writeText "sshd_config" cfg.extraConfig}
             '';
         };
  
positive.code:     v == "without-password" ||
      v == "forced-commands-only" ||
      v == "no";
  
    userOptions = {
      openssh.authorizedKeys = {
  
negative.code: 
              mkdir -m 0755 -p /etc/ssh
  
              if ! test -f /etc/ssh/ssh_host_${hktn}_key; then
                  ${pkgs.openssh}/bin/ssh-keygen -t ${hktn} -b ${toString hktb} -f /etc/ssh/ssh_host_${hktn}_key -N ""
              fi
            '';
  
  