Challenge, Easy,  on  Containers

Docker 101: Pull a Container Image by Digest

The container image repository registry.iximiuz.com/acme/app contains over a dozen tagged versions of an application. Your team has identified that a specific build - pinned by its digest - needs to be pulled for a deployment.

The target image digest is:

sha256:76d822da72eca8d151be12322d54f9ee5ffc330b74f0da29344f06d85761d114
Container image name format visualized: registry domain, repository path, tag, and digest.

Pull the image by digest

Tags are mutable - someone can push a completely different image under the same tag at any time. Digests, on the other hand, are content-addressable hashes that uniquely and immutably identify a specific image build.

Pull the image registry.iximiuz.com/acme/app using the digest above.

Hint 1

To pull an image by digest, use the @ separator instead of : (which is used for tags). The general form is:

docker pull <registry>/<repo>/<name>@<digest>

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-image-by-digest

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

Stream your changes

labctl content push -fw challenge docker-pull-image-by-digest

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

Start challenge