I used gparted and selected gpt under device, advanced & select gpt over msdos(MBR) default partitioning....
But I also install gdisk as that is the command line tool for partitioning and listing partitions, etc.
sudo apt-get install gdisk
Since the BIOS Boot Partition ("bios_grub" flag set in GNU Parted) is used without a filesystem for storing GRUB 2 boot code "unknown" filesystem! may be shown in many Partition tools.