Make k8s.io a default nerdctl namespace and/or user-configurable

[dee-kryvenko]

Preflight Checklist

• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Problem Description

nerdctl -n k8s.io build is long to type.

Proposed Solution

Make k8s.io a default namespace or make it configurable by the user, so in result -n k8s.io don't have to be typed in.

Additional Information

No response

[mook-as]

See relevant minikube PR — we can set worker.containerd.namespace in buildkitd.toml for that.

[jandubois]

See relevant minikube PR — we can set worker.containerd.namespace in buildkitd.toml for that.

That doesn't sounds right. The default namespace should be the same for all nerdctl commands, not just build. The obvious mechanism is to set CONTAINERD_NAMESPACE=k8s.io.

IF #1279 is implemented (and it is currently being considered for the release after 1.1.0), then this would already work (when set on the host).

We could still add a configuration option in the GUI to set this inside the VM, the way we already provide a default for CONTAINERD_ADDRESS.