anchor.diff:    cfg = config.services.vnstat;
   in {
     options.services.vnstat = {
  -    enable = mkOption {
  -      type = types.bool;
  -      default = false;
  -      description = ''
  -        Whether to enable update of network usage statistics via vnstatd.
  -      '';
  -    };
  +    enable = mkEnableOption "update of network usage statistics via vnstatd";
     };
   
     config = mkIf cfg.enable {
  -    users.users.vnstatd = {
  -      isSystemUser = true;
  -      description = "vnstat daemon user";
  -      home = "/var/lib/vnstat";
  -      createHome = true;
  +
  +    environment.systemPackages = [ pkgs.vnstat ];
  +
  +    users = {
  +      groups.vnstatd = {};
  +
  +      users.vnstatd = {
  +        isSystemUser = true;
  +        group = "vnstatd";
  +        description = "vnstat daemon user";
  +      };
       };
   
       systemd.services.vnstat = {
  
positive.code:         RestrictNamespaces = true;
  
          User = "vnstatd";
        };
      };
    };
  }
  
negative.code:         "man:vnstat(1)"
          "man:vnstat.conf(5)"
        ];
        serviceConfig = {
          ExecStart = "${pkgs.vnstat}/bin/vnstatd -n";
          ExecReload = "${pkgs.procps}/bin/kill -HUP $MAINPID";
  