anchor.diff:  
           preStart = ''
               mkdir -p ${cfg.dataDir}
  -            chown ${cfg.user} ${cfg.dataDir}
  +            chown ${user} ${cfg.dataDir}
           '';
   
           exec = ''
  -            ${pkgs.su}/bin/su -s ${pkgs.stdenv.shell} ${cfg.user} \
  +            ${pkgs.su}/bin/su -s ${pkgs.stdenv.shell} ${user} \
                   -c 'HOME="${cfg.dataDir}" ${pkgs.amuleDaemon}/bin/amuled'
           '';
         };
   
  -    environment.systemPackages = [ pkgs.amuleDaemon ];
  -
     };
     
   }
  
positive.code: 
  let
    cfg = config.services.amule;
  in
  
  {
  
negative.code: 
    config = mkIf cfg.enable {
  
      users.extraUsers = mkIf (cfg.user == null) [
        { name = cfg.user;
          description = "AMule daemon";
        } ];
  
      jobs.amuled =
        { description = "AMule daemon";
  