Image size and minimal base images in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why choose minimal base images in Docker?

Which of the following is the main advantage of using minimal base images like alpine in Docker containers?

A They include all development tools by default for easier debugging.

B They automatically update to the latest OS version on container start.

C They guarantee compatibility with all Linux distributions.

D They reduce the final image size, improving download and startup speed.

💡 Hint

Think about what affects container download and deployment speed.

Minimal base images like Alpine are very small, which reduces the image size. Smaller images download faster and start quicker, which is a key benefit in container environments.

💻 Command Output

intermediate

Output of Docker image size command

What is the output of the following command if you have a Docker image named myapp built from alpine base?

docker images myapp --format "{{.Repository}}: {{.Size}}"

A myapp: 500MB

B myapp: 50MB

C myapp: 5MB

D myapp: 1GB

💡 Hint

Alpine base images are known for being very small, around 5MB.

Alpine base images are typically around 5MB, so images built on top of Alpine tend to be small unless large layers are added.

❓ Configuration

advanced

Reducing Docker image size with multi-stage builds

Which Dockerfile snippet correctly uses multi-stage builds to reduce the final image size by excluding build tools?

Docker

FROM golang:1.20 AS builder
WORKDIR /app
COPY . .
RUN go build -o myapp

FROM alpine:latest
COPY --from=builder /app/myapp /usr/local/bin/myapp
ENTRYPOINT ["myapp"]

A The snippet uses multi-stage build to copy only the binary, reducing image size.

B The snippet copies the entire builder image, increasing image size.

C The snippet installs build tools in the final image, increasing size.

D The snippet uses the same base image for both stages, no size reduction.

💡 Hint

Look for copying only the necessary files from the builder stage.

Multi-stage builds allow compiling in one stage and copying only the final binary to a minimal base image, reducing the final image size.

❓ Troubleshoot

advanced

Troubleshooting large Docker image size

You notice your Docker image size is unexpectedly large. Which of the following is the most likely cause?

A Using multi-stage builds to separate build and runtime stages.

B Including unnecessary packages and files in the image layers.

C Using a minimal base image like Alpine.

D Removing cache after package installation.

💡 Hint

Think about what adds extra weight to an image.

Including unnecessary packages and files increases image size. Minimal base images and multi-stage builds help reduce size, and removing cache also helps.

✅ Best Practice

expert

Best practice for minimal Docker images with Python apps

Which Dockerfile approach best minimizes image size for a Python application?

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
CMD ["python", "app.py"]

A Use <code>python:3.12-slim</code> with <code>pip install --no-cache-dir</code> to avoid cache files.

B Use <code>python:3.12</code> full image for maximum compatibility.

C Install packages with cache to speed up builds.

D Use <code>python:3.12-alpine</code> without adjusting pip install options.

💡 Hint

Consider both base image size and package installation options.

Using the slim base image reduces base size, and --no-cache-dir prevents pip from storing cache files, minimizing final image size.