Tilck is a small and deterministic monokernel that currently implements around 100 Linux syscalls in a Linux-compatible way. It’s a good educational tool, but is planned to be a Linux-compatible RTOS kernel. It currently supports statically linked binaries built against musl and boots and runs in about 3 megs of RAM.

One of the goals is to be small enough and simple enough of a codebase to be useful for educational purposes. Another is to eventually be useful in production in embedded systems.