Listing local images in Docker - Mini Project: Build & Apply

Listing Local Docker Images

📖 Scenario: You are working on your computer where you use Docker to manage containers. You want to see which Docker images are saved locally on your machine.

🎯 Goal: Learn how to list all Docker images stored locally using Docker commands.

📋 What You'll Learn

Use the Docker command line interface

List local Docker images with exact command syntax

Display the output of the Docker images list

💡 Why This Matters

🌍 Real World

Developers and system administrators often need to see which Docker images are stored locally to manage disk space and container deployments.

💼 Career

Knowing how to list Docker images is a basic skill for DevOps roles and container management tasks.

1

Open your terminal and check Docker is installed

Type the command docker --version to check if Docker is installed and working.

Docker

# Type docker --version to check Docker installation
# Your code here

Hint

Use the command docker --version to see if Docker is installed.

2

List all local Docker images

Type the command docker images to list all Docker images stored locally on your machine.

Docker

docker --version
# Type docker images to list local Docker images
# Your code here

Hint

The command docker images shows all local images.

3

Add a filter to list images by a specific repository

Use the command docker images nginx to list only images from the nginx repository.

Docker

docker --version
docker images
# Type docker images nginx to filter images by repository
# Your code here

Hint

Adding the repository name after docker images filters the list.

4

Display the final list of all local Docker images

Run the command docker images again to display all local Docker images.

Docker

docker --version
docker images
docker images nginx
# Run docker images to display all images
# Your code here

Hint

The output should show a table with the header REPOSITORY listing all images.

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