Multiple FROM statements in Docker - Mini Project: Build & Apply

Using Multiple FROM Statements in Dockerfiles

📖 Scenario: You are creating a Docker image for a simple web application. You want to use one base image to build the application and another smaller image to run it. This helps keep the final image small and efficient.

🎯 Goal: Build a Dockerfile that uses two FROM statements: one to build the app and one to run the app. You will copy the built files from the first image to the second image.

📋 What You'll Learn

Create a Dockerfile with two FROM statements.

Use node:18 as the first base image to build the app.

Use nginx:alpine as the second base image to serve the app.

Copy the built app files from the first image to the second image.

Expose port 80 in the final image.

💡 Why This Matters

🌍 Real World

Multi-stage Dockerfiles are used to optimize container images by separating build and runtime environments. This reduces image size and improves security.

💼 Career

Understanding multi-stage builds is important for DevOps roles that involve containerization and deployment pipelines.

1

Create the first base image with Node.js

Write the first FROM statement using the exact image node:18. Then create a working directory called /app.

Docker

# Write the first FROM statement and set the working directory
# Your code here

Need a hint?

Start your Dockerfile with FROM node:18 and then add WORKDIR /app on the next line.

2

Add build commands and second base image

Add commands to copy package.json and install dependencies using npm install. Then add a second FROM statement using the exact image nginx:alpine.

Docker

FROM node:18
WORKDIR /app
# Copy package.json and install dependencies
# Add second FROM statement for nginx:alpine
# Your code here

Need a hint?

Use COPY package.json . to copy the file and RUN npm install to install dependencies. Then start the second stage with FROM nginx:alpine.

3

Copy built files and expose port

Copy the built app files from the first stage to /usr/share/nginx/html in the second stage using COPY --from=0 /app/build /usr/share/nginx/html. Then expose port 80.

Docker

FROM node:18
WORKDIR /app
COPY package.json .
RUN npm install
FROM nginx:alpine
# Copy built files from first stage
# Expose port 80
# Your code here

Need a hint?

Use COPY --from=0 to copy files from the first stage. Then add EXPOSE 80 to open the port.

4

Print the final Dockerfile content

Print the entire Dockerfile content as a single string exactly as written in previous steps.

Docker

FROM node:18
WORKDIR /app
COPY package.json .
RUN npm install
FROM nginx:alpine
COPY --from=0 /app/build /usr/share/nginx/html
EXPOSE 80
# Print the Dockerfile content below
# Your code here

Need a hint?

Use a triple-quoted string to store the Dockerfile content and print it.