Why images are blueprints for containers in Docker - See It in Action

Why Images Are Blueprints for Containers

📖 Scenario: You are learning how Docker works. Docker uses images and containers to run applications. Think of an image as a recipe or blueprint, and a container as the cake made from that recipe.

🎯 Goal: Understand how Docker images act as blueprints to create containers by creating a simple Docker image and running a container from it.

📋 What You'll Learn

Create a Dockerfile with a base image

Add a configuration variable for the container

Build a Docker image from the Dockerfile

Run a container from the image and display a message

💡 Why This Matters

🌍 Real World

Developers and system administrators use Docker images to package applications and their environments so they can run anywhere consistently.

💼 Career

Understanding Docker images and containers is essential for roles in DevOps, cloud engineering, and software development to build, deploy, and manage applications efficiently.

1

Create a Dockerfile with a base image

Create a file named Dockerfile with the exact content: FROM alpine:latest to use the Alpine Linux base image.

Docker

# Create a Dockerfile with the base image alpine:latest
# Your code here

Need a hint?

The first line in a Dockerfile usually starts with FROM followed by the base image name.

2

Add a configuration variable for the container

Add a line to the Dockerfile to set an environment variable called MESSAGE with the value Hello from container! using ENV MESSAGE="Hello from container!".

Docker

FROM alpine:latest
# Add an environment variable MESSAGE with value "Hello from container!"
# Your code here

Need a hint?

Use the ENV instruction to set environment variables inside the Docker image.

3

Build a Docker image from the Dockerfile

Write the exact command to build a Docker image named myblueprint from the current directory using docker build -t myblueprint ..

Docker

FROM alpine:latest
ENV MESSAGE="Hello from container!"
# Build the Docker image named myblueprint
# Your code here

Need a hint?

Use docker build with -t to tag the image and . to specify the current directory.

4

Run a container from the image and display a message

Write the exact command to run a container from the image myblueprint that prints the environment variable MESSAGE using docker run --rm myblueprint sh -c 'echo $MESSAGE'.

Docker

# Run the container to print the MESSAGE environment variable
# Your code here

Need a hint?

Use docker run --rm to run and remove the container, and sh -c 'echo $MESSAGE' to print the variable.