containerd-wasm-shims VS containerd

Besides deploying the application locally and deploying to Fermyon Cloud, you can also deploy your Spin application to Kubernetes using the new Containerd integration for Spin.

Yeah, runtimeClass lets you specify which CRI plugin you want based on what you have available. Here's an example from the containerd documentation - you could have one node that can run containers under standard runc, gvisor, kata containers, or WASM. Without runtimeClass, you'd need either some form of custom solution or four differently configured nodes to run those different runtimes. That's how krustlet did it - you'd have kubelet/containerd nodes and krustlet/wasm nodes, and could only run the appropriate workload on each node type.

You can absolutely install the wasm shim without Desktop. (They won't tell you that because Desktop is a revenue stream for Mirantis.)

In your VM or WSL instance that's running Docker, get the shim from here: https://github.com/deislabs/containerd-wasm-shims (You might need to build it yourself)

Then specify the --runtime and --platform arguments like instructed in the doc, but with a slight modification:

--runtime=containerd-wasm-shim=/path/to/containerd/wasm/shim

This works because the container runtime is simply a Go binary, and Go binaries are completely self-contained.

Containerd and nerdctl

Kubernetes on the backend used to utilize docker for much of its container runtime solutions. One of the modular features of Kubernetes is the ability to utilize a Container Runtime Interface or CRI. The problem was that Docker didn't really meet the spec properly and they had to maintain a shim to translate properly. Instead users could utilize the popular containerd or cri-o runtimes. These follow the Open Container Initiative or OCI's guidelines on container formats.

Container Engine: A runtime that executes and manages containers. Docker and containerd are popular container engines.

Multiple container runtimes are supported, like conatinerd, cri-o, or other CRI compliant runtimes.

This is a failed attempt to upstream part of containerd changes: https://github.com/containerd/containerd/pull/8789

Other part of containerd changes waits for gods-know-what: https://github.com/containerd/containerd/pull/9054

But I haven't gave up yet.

containerd is required by kubernetes to handle containers on its behalf. A big thanks to the HostAfrica blog for the information on setting containerd up for debain. So the containerd install will need to happen on both the WSL2 instance and the Raspberry Pis. For WSL2 you can just install containerd directly:

The context deadline exceeded: unknown is also in containerd, and is a known problem.

Get:1 https://download.docker.com/linux/ubuntu focal/stable amd64 containerd.io amd64 1.6.21-1 [28.3 MB]

Docker Desktop adds a bunch of stuff to simplify local development and that’s why it has a larger memory footprint. You don’t use that when deploying but something like https://containerd.io/.