anchor.diff:        };
   
         dataDir = mkOption {
  -        default = ''/home/${cfg.user}/'';
  +        default = ''/home/${user}/'';
           description = ''
             The directory holding configuration, incoming and temporary files.
           '';
         };
   
         user = mkOption {
  -        default = "amule";
  +        default = null;
           description = ''
             The user the AMule daemon should run as.
           '';
  
positive.code: 
          preStart = ''
              mkdir -p ${cfg.dataDir}
              chown ${cfg.user} ${cfg.dataDir}
          '';
  
          exec = ''
              ${pkgs.su}/bin/su -s ${pkgs.stdenv.shell} ${cfg.user} \
                  -c 'HOME="${cfg.dataDir}" ${pkgs.amuleDaemon}/bin/amuled'
          '';
        };
  
      environment.systemPackages = [ pkgs.amuleDaemon ];
  
    };
    
  }
  
negative.code: 
  let
    cfg = config.services.amule;
    user = if cfg.user != null then cfg.user else "amule";
  in
  
  {
  