Multi-stage builds for static sites in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the Dockerfile line to use the official Node.js image for building the static site.

Nginx

FROM [1] as builder

Drag options to blanks, or click blank then click option'

Aalpine:latest

Bnginx:latest

Cubuntu:20.04

Dnode:18-alpine

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'nginx' image for building which lacks Node.js.

Using a full Ubuntu image which is unnecessarily large.

The node:18-alpine image is a lightweight Node.js image suitable for building static sites.

2fill in blank

medium

Complete the command to copy package files before installing dependencies in the build stage.

Nginx

COPY [1] ./

Drag options to blanks, or click blank then click option'

Apackage*.json

Bsrc/

Cdist/

Dnginx.conf

Attempts:

3 left

💡 Hint

Common Mistakes

Copying source code folder before installing dependencies.

Copying nginx configuration in build stage.

Copying package*.json files allows installing dependencies before copying source code.

3fill in blank

hard

Fix the error in the command that copies the built static files from the builder stage to the nginx image.

Nginx

COPY --from=builder [1] /usr/share/nginx/html

Drag options to blanks, or click blank then click option'

A/app/build/

B/build/

C/src/

D/dist/

Attempts:

3 left

💡 Hint

Common Mistakes

Using source folders instead of build output.

Using wrong paths that cause missing files in nginx.

The build output is usually in the /build/ directory inside the builder stage.

4fill in blank

hard

Fill both blanks to set the working directory in the build stage and expose the default nginx port.

Nginx

WORKDIR [1]
EXPOSE [2]

Drag options to blanks, or click blank then click option'

A/app

B8080

C80

D/usr/share/nginx/html

Attempts:

3 left

💡 Hint

Common Mistakes

Exposing port 8080 which is not default for nginx.

Setting working directory to nginx html folder in build stage.

The build stage uses /app as working directory. Nginx exposes port 80 by default.

5fill in blank

hard

Fill all three blanks to complete the multi-stage Dockerfile that builds and serves a static site with nginx.

Nginx

FROM [1] as builder
WORKDIR [2]
RUN npm install && npm run build
FROM [3]
COPY --from=builder /build/ /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

Drag options to blanks, or click blank then click option'

Anode:18-alpine

B/app

Cnginx:stable-alpine

Dubuntu:20.04

Attempts:

3 left

💡 Hint

Common Mistakes

Using ubuntu image for nginx stage which is unnecessarily large.

Not setting working directory before running npm commands.

The first stage uses Node.js alpine image and sets working directory to /app. The second stage uses nginx stable alpine image to serve the built files.

Practice

1. What is the main benefit of using multi-stage builds for static sites with nginx?

easy

A. It automatically updates static files without rebuilding the image.

B. It allows running multiple nginx servers in one container.

C. It reduces the final image size by separating build and serve stages.

D. It enables dynamic content generation inside the nginx container.

Solution

1. Step 1: Understand multi-stage build purpose

   Multi-stage builds separate the build process from the final image, so only necessary files are included.

2. Step 2: Identify benefits for static sites

   This separation reduces the final image size and improves security by excluding build tools from the runtime image.

3. Final Answer:

   It reduces the final image size by separating build and serve stages. -> Option C

4. Quick Check:

   Multi-stage builds = smaller images [OK]

Hint: Remember: build tools stay out of final image for smaller size [OK]

Common Mistakes:

• Thinking multi-stage runs multiple nginx servers
• Believing static files update automatically without rebuild
• Confusing static site builds with dynamic content generation

2. Which Dockerfile snippet correctly copies static files from a builder stage to the nginx stage?

easy

A. COPY --to=builder /app/dist /usr/share/nginx/html

B. COPY /app/dist /usr/share/nginx/html --from=builder

C. COPY /usr/share/nginx/html /app/dist --from=builder

D. COPY --from=builder /app/dist /usr/share/nginx/html

Solution

1. Step 1: Recall correct COPY syntax for multi-stage

   The syntax is COPY --from=stage source_path destination_path.

2. Step 2: Match snippet to syntax

   COPY --from=builder /app/dist /usr/share/nginx/html uses COPY --from=builder /app/dist /usr/share/nginx/html which is correct.

3. Final Answer:

   COPY --from=builder /app/dist /usr/share/nginx/html -> Option D

4. Quick Check:

   COPY --from=stage source dest = correct [OK]

Hint: COPY uses --from=stage before source path [OK]

Common Mistakes:

• Placing --from after paths
• Using --to instead of --from
• Reversing source and destination paths

3. Given this Dockerfile snippet, what will be the size impact on the final image?

FROM node:18 AS builder
WORKDIR /app
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html

medium

A. Final image will be small because only nginx and static files are included.

B. Final image will be empty because build files are not copied.

C. Final image will be large because node is included.

D. Final image will contain both node and nginx layers.

Solution

1. Step 1: Analyze multi-stage build layers

   The builder stage uses node to build files, but the final stage uses nginx:alpine only.

2. Step 2: Understand what is copied to final image

   Only the /app/dist folder from builder is copied into nginx image, so node and build tools are excluded.

3. Final Answer:

   Final image will be small because only nginx and static files are included. -> Option A

4. Quick Check:

   Multi-stage excludes build tools = smaller image [OK]

Hint: Final image excludes builder tools, so size stays small [OK]

Common Mistakes:

• Assuming node stays in final image
• Thinking build files are missing
• Believing both node and nginx layers combine

4. You wrote this Dockerfile but the static files are missing in the nginx container:

FROM node:18 AS builder
WORKDIR /app
COPY . .
RUN npm run build

FROM nginx:alpine
COPY /app/dist /usr/share/nginx/html

What is the error?

medium

A. COPY command misses --from=builder to copy from the build stage.

B. npm run build did not generate files in /app/dist.

C. nginx:alpine image does not support static files.

D. WORKDIR is not set in the nginx stage.

Solution

1. Step 1: Check COPY command in final stage

   The COPY command lacks --from=builder, so it copies from the current stage which is empty.

2. Step 2: Understand multi-stage copy syntax

   To copy files from builder stage, COPY must use --from=builder to access that stage's files.

3. Final Answer:

   COPY command misses --from=builder to copy from the build stage. -> Option A

4. Quick Check:

   Missing --from=builder causes empty copy [OK]

Hint: Always use --from=builder to copy from build stage [OK]

Common Mistakes:

• Forgetting --from=builder in COPY
• Assuming build files auto-copy without --from
• Blaming nginx image for missing files

5. You want to optimize your multi-stage Dockerfile for a static site by minimizing layers and image size. Which approach is best?

hard

A. Combine build and nginx in one stage to avoid copying files.

B. Use a builder stage to create static files, then copy only those files into a minimal nginx image.

C. Install node and build tools inside the nginx image to keep one image.

D. Copy the entire project folder into nginx image to ensure all files are present.

Solution

1. Step 1: Understand multi-stage build best practices

   Best practice is to separate build tools from runtime to keep images small and secure.

2. Step 2: Choose approach minimizing layers and size

   Using a builder stage to create static files, then copying only those files into a minimal nginx image achieves this.

3. Final Answer:

   Use a builder stage to create static files, then copy only those files into a minimal nginx image. -> Option B

4. Quick Check:

   Separate build and serve stages = optimized image [OK]

Hint: Build separately, copy only static files to nginx [OK]

Common Mistakes:

• Combining build and serve increases image size
• Installing build tools in nginx image adds unnecessary layers
• Copying entire project wastes space and layers