Exercise: pull and smoke-test an image

Originally published on docker.learnio.dev — part of the Docker fundamentals course. View this lesson on the original site.

Exercise: pull and smoke-test an image

Practice the chapter 2 verification habit: pull a public image, run it, prove it answers HTTP, and inspect what Docker stored locally.

Work through the steps before you open the solution lesson.

Goal

• pull nginx:stable-alpine from a registry
• run it with a published port on loopback
• confirm HTTP with curl
• inspect tags and digests on your machine

Tasks

1. Pull the image:

docker pull nginx:stable-alpine

2. Run it in the background with name smoke-nginx, publishing container port 80 to 127.0.0.1:8080.

3. Confirm HTTP responds:

curl -I http://127.0.0.1:8080

4. List the image with digest information:

docker image ls --digests nginx

5. Inspect one line of identity metadata:

docker image inspect --format '{{.RepoTags}} {{.RepoDigests}}' nginx:stable-alpine

6. Read recent container logs, then stop and remove the container.

Checklist

• curl returns a successful HTTP status (for example 200)
• docker image ls --digests shows a repo digest for the image
• You can explain the difference between the tag you used and the digest Docker recorded

What is next

Open Solution: pull and smoke-test an image, then take the chapter 2 quiz.

GitHub example

Academy repo: 2-images-layers/exercise-pull-smoke

From Docker fundamentals — Images, layers, tags, and everyday commands