anchor.diff:  
               mkdir -m 0755 -p /etc/ssh
   
  -            if ! test -f /etc/ssh/ssh_host_${hktn}_key; then
  -                ssh-keygen -t ${hktn} -b ${toString hktb} -f /etc/ssh/ssh_host_${hktn}_key -N ""
  +            if ! test -f ${cfg.hostKeyPath}; then
  +                ssh-keygen -t ${hktn} -b ${toString hktb} -f ${cfg.hostKeyPath} -N ""
               fi
             '';
   
  
positive.code: 
          exec =
            ''
              ${pkgs.openssh}/sbin/sshd -h /etc/ssh/ssh_host_${hktn}_key \
                -f ${pkgs.writeText "sshd_config" cfg.extraConfig}
            '';
        };
  
negative.code: 
        hostKeyType = mkOption {
          default = "dsa1024";
          description = ''
            Type of host key to generate (dsa1024/rsa1024/ecdsa521), if
            the file specified by <literal>hostKeyPath</literal> does not
            exist when the service starts.
          '';
        };
  
        hostKeyPath = mkOption {
          default = "/etc/ssh/ssh_host_${hktn}_key";
          description = ''
            Path to the server's private key. If there is no key file
            on this path, it will be generated when the service is
            started for the first time. Otherwise, the ssh daemon will
            use the specified key directly in-place.
          '';
        };
  
        extraConfig = mkOption {
  