Unikernels don't run on microkernels, they run on hypervisors, AKA exokernels. The difference is that microkernels move abstractions like the file system into

Unikernels don't run on microkernels, they run on hypervisors, AKA exokernels. The difference is that microkernels move abstractions like the file system into server processes that still have to be trusted, but are at least isolated; exokernels and hypervisors remove the abstractions from the trusted code base entirely, and just multiplex the hardware directly. Unikernels thus simplify the typical virtualization stack so it looks more like MIT's exokernel research projects, with abstractions in untrusted libraries.