public function flagArchive(\SplFileInfo $archive, $flag)
    {
        // delete all old flags
        $this->unflagArchive($archive);
        // flag the passed archive
        file_put_contents($archive->getPathname() . $flag, $archive->getPathname());
        // set correct user/group for the flag file
        $this->setUserRight(new \SplFileInfo($archive->getPathname() . $flag));
    }