What is "baremetal"

BareMetal is an exokernel-based single address space operating system (OS) created by Return Infinity.

It is written in assembly to achieve high-performance computing with minimal footprint with a JeOS approach. The operating system is primarily targeted towards virtualized environments for cloud computing, or HPCs due to its design as a lightweight kernel (LWK). It could be used as a unikernel.

It was inspired by another OS written in assembly, MikeOS, and it is a current-day example of an operating system that is not written in C or C++, nor based on Unix-like kernels.