pdisk

Apple partition table editor
(the disk must use Apple_partition_scheme. If it uses GUID_partition_scheme, pdisk can not use)

(1) input e
edit device's map
input /dev/disk2
the name of device to change is /dev/disk2

(2input c)
create a partition, with default= Apple_HFS
First block: 64
Length in blocks: 20000
Name of partition: par1

input t
change partition type
input MyPartitionType

(3) input w
write the partition table