Challenge ·Easy

Docker 101: Pull Container Images from Different Registries

Ivan Velichko
by  Ivan Velichko · on
Containers
Pull container images using the 'docker pull' command and explore how the image name determines its source registry and repository.
#container-image#docker#container-registry#containers-101

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In this challenge, you'll pull container images from different registries using the docker pull command.

Container image name format visualized: registry domain, repository path, tag, and digest.

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

Hint 1

The docker pull command downloads an image from a registry. Try docker pull --help to see how to use it.

Hint 2

Docker is smart enough to expand short image names. Running docker pull nginx is equivalent to docker pull docker.io/library/nginx:latest, where docker.io is the registry domain of Docker Hub, and library/nginx is the repository path.

Docker Hub is not the only container registry out there. Let's pull an image from Google Container Registry (GCR) - gcr.io/distroless/static-debian13 is a good candidate.

Hint 3

When pulling from a non-Docker Hub registry, you must use the fully-qualified image reference, including the registry domain and the tag.

To solidify your knowledge, let's pull 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-debian13:nonroot, the domain is gcr.io, the repository path is distroless/static-debian13, 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.

How to Author Challenges on iximiuz Labs

Instead of providing a subpar online editing experience, iximiuz Labs offers a helper CLI tool called labctl, allowing you to use your favorite text editor (or a full-featured IDE) to write content from the comfort of your local machine.

Install labctl CLI

curl -sf https://labs.iximiuz.com/cli/install.sh | sh

This will download and install the latest version of the labctl CLI. You only need to do this once per workstation.

Authorize labctl

labctl auth login

This will open a browser window asking you to authorize labctl to access your account. You need to do it after a fresh install of labctl and repeat it whenever the auth session expires.

Pull challenge content

labctl content pull challenge docker-pull-container-images

This will create a local copy of the challenge content in a directory named docker-pull-container-images. You only need to do this once per challenge.

Stream your changes

labctl content push -fw challenge docker-pull-container-images

Run this command in a separate terminal to continuously upload your changes to the server while editing the challenge in your favorite text editor or IDE.

You can also use labctl to create, list, and delete your content. Learn more about the available commands: labctl content --help

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