documentation VS linuxkit

Both Kata Containers and UTM support virtio-fs, so this is not strictly true. The former can be used as a stand-in replacement for the runtime used by docker desktop[1]. With the latter, one could use a UTM-backed guest as a docker runtime in macOS[2] or run docker directly on the guest[3].

[1] https://github.com/kata-containers/documentation/blob/master...

[2] https://www.codeluge.com/post/setting-up-docker-on-macos-m1-...

[3] https://www.lifeintech.com/2021/11/03/docker-performance-on-...

For services with increased security requirements, it is recommended to use a low-level run-time with a high degree of isolation (gVisior, Kata-runtime)

On the official Kata repo, I found a tutorial only for manually deployed Kubernetes on GCE.

This is new and may not be used much, but it is possible to use part of Kata with part of Firecracker. https://github.com/kata-containers/documentation/wiki/Initia...

If it's using firecracker, it's probably using KVM virtualization while ensuring that the memory the VM consumes is not pinned... that is, that the VM can be swapped out of memory. For reference, firecracker was created by AWS to run and secure AWS Lambda. The hypervisor is written in rust and uses seccomp to eliminate unnecessary system calls. They open sourced it a few years back.

What you gain is a stronger security boundary. Just FYI, since 2019, you can also do this in Kubernetes using Kata containers which will happily shim firecracker. The setup is not simple though.

https://github.com/kata-containers/documentation/wiki/Initia...

Overall, fly.io building infrastructure on this pattern is fantastic and making it accessible is fantastic. Looking forward to seeing how this continues to evolve and am happy to see more infra build on top of firecracker. Very exciting!

Another project that aims to deliver this is Linuxkit (https://github.com/linuxkit/linuxkit). All the components they ship are written in memory safe languages (usually Go) and run as containers under containerd. You can build a custom image very easily, fully defined as a YAML file.

docker-the-company maintained https://github.com/linuxkit/linuxkit when I worked there. I have no idea who maintains it now, but it looks like it is still active (presumably still docker-the-company, since their adopters list [1] lists docker desktop).

[1]: https://github.com/linuxkit/linuxkit/blob/master/ADOPTERS.md

LF-Edge EVE project leverages Linuxkit to create custom OSs for Edge Devices which in turn leverages Containers as Lego Blocks

LinuxKit - Docker

Behind the scenes Docker Desktop for Mac spawns a linuxkit VM with a bit of extra stuff like NFS to enable mounting Mac paths into containers. In the Docker Desktop settings you'll find the current resource assignment for that VM. That is pretty much reserved for docker so that it does not have to compete with MacOS processes for available resources.

That said... you might want to check out linuxkit

The definition of what a unikernel is needs to be narrowed down, a lot of these projects in the space (not all the ones listed above) have material differences that are not clear:

- some run only one language

- some require recompilation

- some essentially swap out libraries, others do something closer to dropping your already mostly static binary in a minimal disk image

- some build pid1 processes, others VMs images

Anyway, here are some additional entries in the space:

- https://ssrg-vt.github.io/hermitux/

- https://github.com/linuxkit/linuxkit (more embedded/minimal VM than unikernel)

- https://nabla-containers.github.io/ (runs on Solo5)

I am going through using Linuxkit to build AMIs for cloud providers now. I wouldn’t necessarily class linuxkit as a universal project because it doesn’t have the hallmark blurring of user and kernel space or kernel-as-a-library but you can customize the kernel so it’s an adjacent idea, and I think it’s the one most likely to be in actual use at non-hyperscalers.

I believe there is growing interest in providing leaner, "trimmed" runtimes for services deployed to the cloud. Today, this is seen largely by specializing the Linux kernel for, for example, container services[0] or in general[1], as much as that is possible (the paper above covers this problem in greater detail). But, Unikernels in themselves are not yet widely adopted. This is the space Unikraft is aiming to enter, providing the ultimate level of specialization for a target application.

It's clear that bigger players, such as Red Hat[2] are interested in the topic of unikernels, and that cloud providers are preparing for this future too [3].

[0]: https://github.com/linuxkit/linuxkit