Docker Containerization Dockerfile and Image Building 2

Question 1

What defines a multi-stage Docker build?

Accepted Answer

Using multiple FROM instructions in one Dockerfile to copy artifacts between stages and produce a lean final image

Answer

Multi-stage builds use multiple FROM instructions, allowing intermediate stages (e.g., a compiler image) to build artifacts that are then copied into a minimal final image, reducing image size.

Question 2

Which 'docker build' flag allows you to stop at a specific named stage in a multi-stage Dockerfile?

Accepted Answer

--target

Answer

The --target flag tells Docker to build only up to and including the specified named stage, which is useful for debugging or producing intermediate artifacts.

Question 3

How does Docker layer caching improve build performance?

Accepted Answer

Docker reuses cached layers from previous builds when Dockerfile instructions and their context have not changed

Answer

Docker caches each image layer; if an instruction and its inputs haven't changed since the last build, Docker reuses the cached layer and skips re-executing that step.

Question 4

Which base image is most commonly recommended for minimizing Docker image size in production?

Accepted Answer

alpine:latest

Answer

Alpine Linux is a minimal distribution (~5MB) that is widely used as a base image to keep Docker images small, reducing pull times and attack surface.

Question 5

What happens to Docker's build cache when a Dockerfile instruction changes?

Accepted Answer

The changed layer and all subsequent layers are invalidated and rebuilt

Answer

Docker invalidates the cache starting at the changed instruction, so that changed layer and every layer after it are rebuilt to ensure correctness.

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Docker Containerization Dockerfile and Image Building 2