Comment by valyala

There is no need in the operating system to run Unikernels. Every Unikernel includes parts of operating system needed for interacting with the underlying hardware. So Unikernels can run on bare metal if they know how to interact with the underlying hardware (i.e. if they have drivers for that hardware). Usually Unikernels are targeted to run on virtual machines because virtual machines have unified virtualised hardware. This allows running the same Unikernel on virtual machines across multiple cloud providers, since they have similar virtual hardware.