    # File lib/facets/more/minitar.rb, line 394
        def mkdir(name, opts = {})
          raise ClosedStream if @closed
          name, prefix = split_name(name)
          header = { :name => name, :mode => opts[:mode], :typeflag => "5",
                     :size => 0, :gid => opts[:gid], :uid => opts[:uid],
                     :mtime => opts[:mtime], :prefix => prefix }
          header = Archive::Tar::PosixHeader.new(header).to_s
          @io.write(header)
          nil
        end