Listing local images in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the command to list all local Docker images?

You run the command docker images on a system with three images: alpine:latest, ubuntu:20.04, and nginx:1.21. What will the command output show?

Docker

docker images

A

REPOSITORY   TAG       IMAGE ID       CREATED        SIZE
alpine       latest    abc123def456   2 weeks ago    5.5MB
ubuntu       20.04     def456abc123   3 weeks ago    72.9MB
nginx        1.21      123abc456def   1 week ago     133MB

B

REPOSITORY   TAG       IMAGE ID       CREATED        SIZE
alpine       latest    abc123def456   2 weeks ago    5.5MB
ubuntu       20.04     def456abc123   3 weeks ago    72.9MB

C

REPOSITORY   TAG       IMAGE ID       CREATED        SIZE
nginx        1.21      123abc456def   1 week ago     133MB

D

REPOSITORY   TAG       IMAGE ID       CREATED        SIZE
none         none      none          none           none

💡 Hint

The docker images command lists all local images with their tags and sizes.

The docker images command shows all local images. Since there are three images, all appear in the output with their details.

🧠 Conceptual

intermediate

Which Docker command lists only image IDs of local images?

You want to see just the image IDs of all local Docker images without other details. Which command will do this?

A docker images --format "{{.ID}}"

B docker images --ids

C docker list images --id-only

D docker images -q --all

💡 Hint

Use the --format option with a Go template to customize output.

The docker images --format "{{.ID}}" command lists only the image IDs. Option A is close but -q alone lists IDs; --all is not needed here.

❓ Troubleshoot

advanced

Why does docker images show no images after pulling one?

You run docker pull nginx successfully, but then docker images shows no images. What could cause this?

A The image pull failed silently and no image was downloaded.

B You are connected to a different Docker context or daemon than where the image was pulled.

C Docker images command requires sudo privileges to show images.

D The image was pulled but immediately deleted by a cleanup process.

💡 Hint

Check if Docker is using the same context or daemon for both commands.

Docker contexts or daemons can be switched. Pulling an image in one context and listing images in another shows no images.

🔀 Workflow

advanced

What is the correct sequence to list images, remove one, then verify removal?

You want to list all images, remove the image with ID abc123, then confirm it is removed. Which sequence of commands is correct?

A 2,1,3

B 1,3,2

C 1,2,3

D 3,1,2

💡 Hint

You must list images first to see what is available before removing.

First list images to confirm the image ID, then remove it, then list again to verify removal.

✅ Best Practice

expert

Which command safely lists all local images including intermediate layers?

You want to see all local Docker images including intermediate layers that are not tagged. Which command achieves this?

A docker images --include-untagged

B docker images --filter intermediate=true

C docker images --show-intermediate

D docker images --all

💡 Hint

Use the option that shows all images, not just tagged ones.

The --all option lists all images including intermediate layers. Other options do not exist or are invalid.