It requires to understand the linux booting mechanism a little bit better.
After booting, the kernel initializes the device drivers, and after that it starts the first process on the system. By default, it is /sbin/init. From this point, the kernel doesn't do anything by own, only executes the requests of the processes.
You can override this default setting by an init=/path/to/your/binary in the kernel boot parameters. These parameters you have to give to your bootloader (which is probably grub).
If you want a simple command prompt with a shell, you can give init=/bin/bash to your boot loader.