Challenge, Easy,  on  Containers

List All Tags in a Container Repository

Ivan Velichko
by  Ivan Velichko

A single container repository can have dozens or even hundreds of tags in it: semantic version releases (v1.0.0, v1.0.1, v1.0.2-rc.1), per-commit builds (sha-1234567890), moving pointers like latest or stable, etc. Being able to list those tags is useful when you need to see what was published, pick the right version to deploy, check whether a CI build pushed the expected image, or clean up old tags without guessing.

The registry API allows you to list all tags in a repository using the GET /v2/<repo>/tags/list endpoint, but surprisingly Docker still doesn't have a command to do this via the CLI.

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

In this challenge, you'll practice listing the tags in a container repository.

Your task is to enumerate all tags currently published under the registry.iximiuz.com/acme/search-indexer repository and save them to ~/tags.txt - one tag per line (tag names only - no registry domain, no repository path, no digests). The order doesn't matter, but the set of tag names must match the repository's tag list exactly.

Hint 1: Tools for the job

While docker doesn't have a command to list tags in a remote repository, there are several tools that can help you - crane, regctl, and even a plain curl call to the registry API.

Hint 2: Calling the registry API

The registry API exposes the tag list as a JSON document at the /v2/<repo>/tags/list endpoint.

To construct the full URL, you need to combine the scheme (https://), the registry domain (registry.iximiuz.com), the repository path (with slashes), and the tags listing endpoint (/tags/list).

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 list-tags-in-container-repository

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

Stream your changes

labctl content push -fw challenge list-tags-in-container-repository

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