I'm trying to create a persistence USB.

I follow the instructions on the Kali Linux website that tells you how to do it.

I open up the terminal. type 'sudo su'. Then I type:

end=7gb (enter)

read start _ < <(du -bcm kali-linux-1.1.0a-amd64.iso | tail -1); echo $start (enter, and at this point I get: du: cannot access 'kali-linux-1.1.0a-amd64.iso)

parted /dev/sdb mkpart primary $start $end

How to I find out what I'm supposed to put after '-bcm'? I'm sure it's kali-linux-1.1.0a-amd64.iso. That's the iso file I have on my windows machine that I would have used to put on the USB.