If you're into unikernels, rumpkernels[0] are the least-modification-required approach I've seen.
Basically, if you compile your program with a minimally (as minimal as is possible) modified compiler, you get "rumprunnable" output. there's a list of popular packages built to run on rump kernels[1] (Rust is supported[2]). I haven't tried to use the toolchain yet, but it's pretty appealing to me.
The biggest issue is that rumpkernels seem to not be in developed anymore. I can't tell if the entire is just off somewhere being productive with their rumpkernels and are happy or if no one is around at all. The Github organization[3]'s repos all seem to not have been changed in a while either.
Outside of rumpkernels, Nabla containers[4] also look interesting to me. They're built on Solo5[5], but the only microkernels on there are currently MirageOS (for OCaml) and IncludeOS (C++?). Nabla looks amazing (containers look like a great fit and they seemed to have improved ergonomics massively), but the limitations[6] are intense.
[0]: https://github.com/rumpkernel/wiki/wiki/Info:-FAQ
[1]: https://github.com/rumpkernel/rumprun-packages
[2]: https://github.com/rumpkernel/rumprun-packages/tree/master/r...
[3]: https://github.com/rumpkernel
[4]: https://nabla-containers.github.io/
I'm hoping we're be able to port libuv to IncludeOS (which should be doable, much like libuv IncludeOS is eventdriven). Then we should be able to get Node up and running. Running Node.js through IncludeOS on Nabla could be interesting in a "FaaS" context.
Last I heard the author of Rumprun has picked up beer brewing full time and isn't interested in maintaining the project.
It would be great if someone where to pick it up.
OSv is also very relevant. They provide a much richer and more compatible runtime environment compared to IncludeOS (I think they even have zfs). And OSv is pretty active these days, so if you looking for a way to run some high performance stuff OSv is worth looking into.
Thanks for mentioning OSv[0], I'd never heard about it before.
I'm excited to see what happens with Nabla, I read the accompanying paper and was pretty excited about the possibilities. Nabla's greatest strength is it's ergonomics, IMO, though rumprun comes close (someone took some time to make dockerized containers for it).
[EDIT] - looking at OSv's (primary?) tool capstan[1], I'm not sure it's quite the same, it seems more like linuxkit[2] than rumprun. Maybe my intuition is wrong, but it seems much more like you're bringing along a stripped down OS than you're writing a program meant to interact with a shared unikernel. The distinction is so fuzzy in my head I'm not sure there is one, but it feels different.
[0]: http://osv.io/