I have a bootable Linux on a 2 GB USB stick with 770 MB used, and another stick that is 1 GB. The aim is to put the files on the 1 GB stick and make it boot properly into Linux and run the software copied from the 2 GB stick.
The hard part is that there is no ISO to start with. And of course if I create an ISO or dd image from the original, it will be 2 GB and so will not fit on the 1 GB stick. So that seems to rule out using unetbootin, doesn't it?
There is a Linux kernel file copied from the 2 GB stick. The challenge is to set the boot process to find it on the 1 GB stick.