Pulling Container Images Using ctr

In this containerd challenge, you'll need to pull images from different container registries using the ctr command.

Let's start with a simple one - pull an nginx image from Docker Hub.

Hint 1 💡

Unlike with the docker command, you can't just run ctr pull nginx. The ctr command has a subcommand for working with images. Try ctr image --help to see how to use it.

Hint 2 💡

The ctr image pull command takes a fully-qualified image reference as an argument. The famous docker run nginx is actually a shorthand for docker run docker.io/library/nginx:latest. Try adapting this sacred knowledge to ctr image pull.

Docker Hub is not the only container registry supported by containerd. Let's try pulling an image from another source - Google Container Registry (GCR) - gcr.io/distroless/static-debian12 is a good candidate.

Hint 3 💡

Getting a cryptic failed to resolve reference: object required error? Make sure you're using the fully-qualified image reference, including the tag!

To solidify your knowledge, let's try pulling an image from one more registry - the GitHub Container Registry (GHCR). This time, you'll need to come up with the image example yourself.

Hint 4 💡

A fully-qualified image reference consists of three parts: the registry domain, the repository path, and the tag. For example, in gcr.io/distroless/static-debian12:nonroot, the domain is gcr.io, the repository path is distroless/static-debian12, and the tag is nonroot.

Hint 5 💡

The GitHub Container Registry domain is ghcr.io.

Hint 6 💡

On GHCR, the image repository path is typically the same as the code repository path. For example, images of the github.com/openfaas/faas-netes project are hosted at ghcr.io/openfaas/faas-netes.