It is available in Ubuntu Trusty Tahr 14.04.1 Live Iso.
Open a terminal.
The gdisk program employs a user interface similar to that of Linux's fdisk, but gdisk modifies GPT partitions. It also has the capability of transforming MBR partitions or BSD disklabels into GPT partitions. Like the original fdisk program, gdisk does not modify disk structures until you explicitly write them to disk, so if you make a mistake, you can exit from the program with the 'q' option to leave your partitions unmodified.
When creating a fresh partition table, certain considerations may be in order:
For data disks, and for boot disks used on BIOS-based computers with GRUB as the boot loader, partitions may be created in whatever order and in whatever sizes are desired.
Boot disks for EFI-based systems require an EFI System Partition (gdisk internal code 0xEF00) formatted as FAT-32.
Some boot loaders for BIOS-based systems make use of a BIOS Boot Partition (gdisk internal code 0xEF02), in which the secondary boot loader is stored, possibly without the benefit of a filesystem.
If Windows is to boot from a GPT disk, a partition of type Microsoft Reserved (gdisk internal code 0x0C01) is recommended. This partition should be about 128 MiB in size. It ordinarily follows the EFI System Partition and immediately precedes the Windows data partitions.
Some OSes' GPT utilities create some blank space (typically 128 MiB) after each partition. The intent is to enable future disk utilities to use this space. Such free space is not required of GPT disks, but creating it may help in future disk maintenance.
-l List the partition table for the specified device and then exits.
b Save partition data to a backup file.
c Change the GPT name of a partition.
d Delete a partition.
i Show detailed partition information.
l Display a summary of partition types.
n Create a new partition.
o Clear out all partition data.
p Display basic partition summary data.
q Quit from the program without saving your changes.
r Enter the recovery & transformation menu.
s Sort partition entries.
t Change a single partition's type code.
v Verify disk.
w Write data.
? Print the menu.