Challenge - Dockerfile
- Docker & Kubernetes course
- Beginner
- Lesson 78/82
- 5 min
Write a Dockerfile for a web application.
Challenge: a production-ready Dockerfile
In this challenge you'll combine all the good practices for a Node.js API in a single Dockerfile:
- A small base image with a pinned version
- Cache-friendly order (
package*.jsonfirst) - Only production dependencies
- A non-root user
- A start command in exec form
FROM node:20-alpine
ENV NODE_ENV=production
WORKDIR /app
COPY package*.json ./
RUN npm ci --omit=dev
COPY --chown=node:node . .
USER node
EXPOSE 3000
CMD ["node", "server.js"]Practice Write the Dockerfile
Write the Dockerfile from the card: node:20-alpine; ENV NODE_ENV=production; WORKDIR /app; copy package*.json and run npm ci --omit=dev; copy the code with --chown=node:node; USER node; EXPOSE 3000; node server.js in exec form.
Starter code
# buraya yazSample solution
FROM node:20-alpine
ENV NODE_ENV=production
WORKDIR /app
COPY package*.json ./
RUN npm ci --omit=dev
COPY --chown=node:node . .
USER node
EXPOSE 3000
CMD ["node", "server.js"]Expected output
[+] Building 7.1s (12/12) FINISHED => naming to docker.io/library/api:1.0 done
Practice Add a .dockerignore
Write a .dockerignore for the same project: exclude node_modules, .git, .env, npm-debug.log and Dockerfile.
Starter code
# buraya yazSample solution
node_modules
.git
.env
npm-debug.log
DockerfileExpected output
=> [internal] load .dockerignore => => transferring context: 21.3kB
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 In the Dockerfile above, which step reruns if only server.js changes?
- Only FROM
- None
- COPY --chown=node:node . . and after Correct answer
- All of them including npm ci
Explanation: Since package*.json didn't change, npm ci comes from the cache.
2 Install only the production dependencies.
Question
RUN npm ci ____
Answer
RUN npm ci --omit=devExplanation: npm ci --omit=dev skips devDependencies.
3 Match the practices with their purposes.
| Term | Meaning |
|---|---|
node:20-alpine |
Small, pinned base |
package*.json first |
Cache |
USER node |
Least privilege |
["node", "server.js"] |
Signal handling |