Set docker local registry credentials for default service account

[alborotogarcia]

Hi k3d team!

Having in mind that there are rate limits from mirantis on docker hub, I find that it may be useful having docker config json already set to k3d default service account, eg. via a path param or by simply introducing them at k3d boostrap, so that any image could be pulled using docker user credentials by default.

And I don't know if local docker registry could be also used as storage to cache images, as I see is done for rancher/k3d-proxy and rancher/k3s images.

[iwilltry42]

Hi @alborotogarcia , thanks for starting this discussion!
k3d itself doesn't manage things inside the cluster per-se, but we could do some "kubectl magic" once the cluster is up to inject this kind of changes. That may be unstable though.
You can mount auto-deploy manifests to the cluster, but there I'm not sure if you'd be able to modify the default service account (it's namespaced anyway, isn't it?).

Anyway, a better solution, that would work right away for the whole cluster is, to add your dockerhub auth credentials to containerd using the registry-config (registries.yaml), similar to how it's described here: https://k3d.io/usage/guides/registries/#authenticated-registries (also see https://rancher.com/docs/k3s/latest/en/installation/private-registry/ -> allows you to configure containerd like described here: containerd/cri#835 (comment)).