Reducing final image size by 80 percent in Docker - Mini Project: Build & Apply

Reducing final image size by 80 percent

📖 Scenario: You are working on a Docker project where the final image size is too large. Large images take longer to download and use more storage. Your goal is to reduce the final Docker image size by 80% using best practices.

🎯 Goal: Build a Dockerfile that creates a small final image by using a multi-stage build and a minimal base image.

📋 What You'll Learn

Create a Dockerfile with a multi-stage build

Use python:3.12-slim as the base image in the first stage

Use python:3.12-alpine as the base image in the final stage

Copy only necessary files from the build stage to the final stage

Install only required dependencies in the final image

Print the final image size after building

💡 Why This Matters

🌍 Real World

Reducing Docker image size helps in faster deployments, less storage use, and better performance in cloud environments.

💼 Career

DevOps engineers and developers often optimize Docker images to improve CI/CD pipelines and production deployments.

1

Create the initial Dockerfile with a base image

Create a Dockerfile starting with the base image python:3.12-slim using the FROM instruction.

Docker

# Create a Dockerfile starting with FROM python:3.12-slim
# Your code here

Need a hint?

Use the FROM keyword followed by python:3.12-slim to specify the base image.

2

Add a build stage with dependencies installation

Add a build stage named builder using FROM python:3.12-slim AS builder. Then add a line to install pip packages flask and requests using RUN pip install flask requests.

Docker

FROM python:3.12-slim
# Add a build stage named builder and install flask and requests
# Your code here

Need a hint?

Use AS builder to name the stage. Use RUN pip install flask requests to install packages.

3

Create the final minimal image stage

Add a final stage starting with FROM python:3.12-alpine. Copy the installed packages from the builder stage using COPY --from=builder /usr/local/lib/python3.12/site-packages /usr/local/lib/python3.12/site-packages. Also copy the /usr/local/bin folder from builder to the final image. Set the default command to python3.

Docker

FROM python:3.12-slim AS builder
RUN pip install flask requests
# Add final stage with python:3.12-alpine and copy installed packages
# Your code here

Need a hint?

Use COPY --from=builder to copy files from the build stage. Use CMD ["python3"] to set the default command.

4

Build the image and print its size

Build the Docker image with tag small-python-app using docker build -t small-python-app .. Then run docker images small-python-app --format "{{.Size}}" to print the final image size.

Docker

# Build the image with tag small-python-app
# Print the image size
# Your code here

Need a hint?

Use docker build -t small-python-app . to build. Use docker images small-python-app --format "{{.Size}}" to show size.