parted

Examples

parted -a optimal /dev/sda

... fires up parted against the /dev/sda disk

(parted)mklabel gpt

... makes a GPT label for that disk

(parted)set 1 bios_grub on

... makes partition 1 a GRUB-bootable partition on a PC-BIOS

(parted)set 2 boot on

... marks partition 2 boot partition as the EFI System Partition