Listing local images in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What command lists all local Docker images on your machine?

The command docker images shows all Docker images stored locally.

beginner

What information does docker images display?

It shows the repository name, tag, image ID, creation date, and size of each local image.

intermediate

How can you list images with a specific repository name?

Use docker images <repository_name> to filter images by repository.

intermediate

What does the -a or --all option do with docker images?

It shows all images including intermediate image layers, not just the top-level images.

advanced

How do you list images with their digests?

Use docker images --digests to see image digests along with other details.

Which command lists all local Docker images?

A docker ps

B docker images

C docker run

D docker pull

docker images lists all local images. docker ps lists running containers.

What does the docker images -a command show?

A All images including intermediate layers

B Only images from Docker Hub

C Only running containers

D Only top-level images

The -a option shows all images including intermediate layers.

How do you filter images by repository name?

A docker images --filter repository=name

B docker images -f name

C docker images name

D docker images --name

Using docker images <repository_name> filters images by repository.

Which field is NOT shown by default in docker images output?

A Image digest

B Tag

C Repository

D Image ID

Image digest is shown only with --digests option.

What does the Tag column represent in docker images?

A The creation date

B The image size

C The container ID

D The version or variant of the image

Tag shows the version or variant of the image.

Explain how to list all local Docker images and what key details you see in the output.

Think about the command that shows images and what columns it displays.

Describe how to filter Docker images by repository name and why this might be useful.

Consider how to narrow down the list to images from one source.

Practice

1. What does the docker images command do?

easy

A. Lists all local Docker images stored on your machine

B. Shows running Docker containers

C. Deletes all Docker images

D. Builds a new Docker image from a Dockerfile

Solution

1. Step 1: Understand the purpose of docker images

   This command is designed to show all Docker images saved locally on your computer.

2. Step 2: Differentiate from other Docker commands

   Commands like docker ps show running containers, and docker build creates images, so they are not correct here.

3. Final Answer:

   Lists all local Docker images stored on your machine -> Option A

4. Quick Check:

   docker images = list local images [OK]

Hint: Remember: images = saved pictures, containers = running apps [OK]

Common Mistakes:

• Confusing images with running containers
• Thinking it deletes images
• Mixing it up with build command

2. Which of these is the correct syntax to list all local Docker images?

easy

A. docker list images

B. docker image list -a

C. docker show images

D. docker images

Solution

1. Step 1: Recall the exact command for listing images

   The standard command is docker images to list local images.

2. Step 2: Check other options for correctness

   docker list images and docker show images are invalid commands. docker image list -a is a valid command but lists all images including intermediate layers, which is more advanced than the basic listing.

3. Final Answer:

   docker images -> Option D

4. Quick Check:

   Correct syntax = docker images [OK]

Hint: Use exact command: docker images, no extra words [OK]

Common Mistakes:

• Adding extra words like 'list' or 'show'
• Using incorrect flags or subcommands
• Confusing 'image' and 'images'

3. What will be the output of the command docker images if you have two images named app with tags v1 and v2?

medium

A. It will list images but without tags

B. It will list only the latest image

C. It will list both images with their tags and IDs

D. It will show an error about duplicate image names

Solution

1. Step 1: Understand how Docker images are listed

   The docker images command shows all images, including multiple tags for the same image name.

2. Step 2: Confirm output details

   Both images named app with tags v1 and v2 will appear separately with their tags and image IDs.

3. Final Answer:

   It will list both images with their tags and IDs -> Option C

4. Quick Check:

   docker images lists all tags separately [OK]

Hint: Each tag is a separate image entry in the list [OK]

Common Mistakes:

• Assuming only one tag shows
• Expecting an error for duplicate names
• Thinking tags are hidden

4. You ran docker images -l but got an error. What is the problem?

medium

A. The -l flag is invalid for docker images

B. You need to run the command as root

C. You must specify an image name with -l

D. The Docker daemon is not running

Solution

1. Step 1: Check the meaning of -l flag

   The -l flag is not a valid option for docker images. It causes a syntax error.

2. Step 2: Consider other possible causes

   Running as root or daemon status would cause different errors. The -l flag does not require an image name.

3. Final Answer:

   The -l flag is invalid for docker images -> Option A

4. Quick Check:

   Invalid flag = error [OK]

Hint: Use only supported flags with docker images [OK]

Common Mistakes:

• Assuming -l lists latest images
• Thinking root permission fixes flag errors
• Confusing daemon errors with syntax errors

5. You want to list all local Docker images but only show the repository and tag columns. Which command should you use?

hard

A. docker images --filter "repository,tag"

B. docker images --format "{{.Repository}}:{{.Tag}}"

C. docker images --only repository tag

D. docker images --columns repository tag

Solution

1. Step 1: Understand formatting option in docker images

   The --format flag lets you customize output columns using Go template syntax.

2. Step 2: Check each option's validity

   --format "{{.Repository}}:{{.Tag}}" correctly formats output to show only repository and tag. Other options are invalid or unsupported.

3. Final Answer:

   docker images --format "{{.Repository}}:{{.Tag}}" -> Option B

4. Quick Check:

   Use --format with Go templates for custom columns [OK]

Hint: Use --format with {{.Repository}} and {{.Tag}} [OK]

Common Mistakes:

• Using unsupported flags like --only or --columns
• Confusing --filter with formatting
• Incorrect template syntax