Image layers concept in Docker - Mini Project: Build & Apply

Understanding Docker Image Layers

📖 Scenario: You are learning how Docker builds images in layers. Each command in a Dockerfile creates a new layer. This helps Docker reuse layers and save space.Imagine you want to create a Docker image for a simple web server. You will write a Dockerfile step-by-step to see how layers are created.

🎯 Goal: Build a Dockerfile step-by-step to understand how each command creates a new image layer. You will write commands to create the base image, add files, install packages, and finally run the server.

📋 What You'll Learn

Write a Dockerfile with exact commands

Use FROM to set the base image

Use RUN to install packages

Use COPY to add files

Use CMD to set the container start command

💡 Why This Matters

🌍 Real World

Docker image layers help save space and speed up builds by reusing unchanged layers.

💼 Career

Understanding image layers is essential for efficient Dockerfile writing and optimizing container builds in DevOps roles.

1

Create the base image layer

Write a Dockerfile line that uses FROM to set the base image to python:3.12-slim.

Docker

# Write the FROM command to set base image
# Your code here

Need a hint?

The FROM command sets the starting point for your image.

2

Add a layer to copy your app files

Add a line to the Dockerfile that uses COPY to copy the local folder app/ to /app inside the image.

Docker

FROM python:3.12-slim
# Add COPY command to copy app folder
# Your code here

Need a hint?

The COPY command adds your application files into the image.

3

Add a layer to install dependencies

Add a line to the Dockerfile that uses RUN to install the package flask using pip.

Docker

FROM python:3.12-slim
COPY app/ /app
# Add RUN command to install flask
# Your code here

Need a hint?

The RUN command runs commands inside the image to install software.

4

Set the command to run the app

Add a line to the Dockerfile that uses CMD to run python /app/server.py when the container starts.

Docker

FROM python:3.12-slim
COPY app/ /app
RUN pip install flask
# Add CMD command to run the server
# Your code here

Need a hint?

The CMD command tells Docker what to run when the container starts.