parted
Examples with 2 × 2 TB hard disk drives as MBR,
for a virtual 4 TB with data and 32 GB of swap as GPT.
MBR
parted /dev/sda
mktable msdos
mkpart primary 1 2000399
parted /dev/sdb
mktable msdos
mkpart primary 1 2000399
Warning
The first megabyte makes room for an embedded bootloader.
GPT
parted /dev/md0
mktable gpt
mkpart data 1 3966128
mkpart swap 2 4000527
Note
Start offset of a partition can be inferior than actual free space beginning.