private function changeDirsAndFilesOwnerships($app)
 {
     logMessage(L_USER, "Changing ownerships of directories and files");
     foreach ($this->install_config['chown_items'] as $item) {
         $chmown_item = $app->replaceTokensInString($item);
         if (!OsUtils::chown($chmown_item)) {
             return "Failed to change ownership for {$chmown_item}";
         }
     }
 }