What have I to do to formating BBB Board with two partitions for data?

Hallo all,

I’m new in using Linux and BBB Board.
I will split the data area into two partitions one for the Linux kernal and one for my own data. I use only a default reboot SD-Card for reprogramming my BBB board.
Exist there a command to Change the Format of the emmc, while the board has a valid Linux installed?

In use in my own application only the kernal module “BCM1CM001” and not the Interface module with SD-Card. I have only an Adapter for programming the board via SD-Card so I don’t have an additional memory.

Can you help me?

Best regards