Docker layer caching in CI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Docker layer caching in CI?

Docker layer caching in CI means saving parts of the Docker image build steps so that future builds can reuse them. This makes builds faster by not repeating unchanged steps.

beginner

How does Docker layer caching speed up builds?

Docker breaks images into layers for each build step. If a layer hasn’t changed, Docker reuses it instead of rebuilding. This saves time and computing resources.

intermediate

Why is Docker layer caching challenging in CI environments?

CI systems often start fresh environments for each build, so cached layers are lost unless explicitly saved and restored between builds.

intermediate

Name a common method to enable Docker layer caching in CI pipelines.

One common method is to push built image layers to a remote Docker registry after a build, then pull them before the next build to reuse cached layers.

intermediate

What is the role of the Dockerfile order in layer caching?

The order of commands in a Dockerfile affects caching. Changes early in the file invalidate all following layers, so placing stable commands first helps maximize cache reuse.

What happens if a Docker build step changes in a CI pipeline with caching enabled?

A The build fails

B All steps are rebuilt from the start

C No steps are rebuilt

D Only the changed step and following steps are rebuilt

Docker rebuilds the changed step and all steps after it, but reuses cached layers before the change.

Why might Docker layer caching not work automatically in CI systems?

A CI systems delete all files after each build

B Docker does not support caching

C CI environments are often clean and do not keep previous cache layers unless saved

D Dockerfiles are incompatible with CI

CI environments usually start fresh, so cached layers must be saved and restored explicitly.

Which of these helps improve Docker layer caching efficiency?

A Randomizing Dockerfile commands

B Placing frequently changing commands at the end of the Dockerfile

C Using only one RUN command

D Avoiding any caching

Placing changing commands at the end keeps earlier layers stable and cached.

What is a common way to share Docker cache between CI builds?

A Using a shared Docker registry to push and pull images

B Rebuilding everything every time

C Disabling Docker caching

D Using a different Dockerfile each time

Pushing and pulling images from a registry allows reuse of cached layers across builds.

Which Docker command helps to build an image using cache from a remote registry?

A docker build --cache-from

B docker run --cache

C docker pull --cache

D docker push --cache

The --cache-from option tells Docker to use layers from a specified image as cache.

Explain how Docker layer caching works and why it is useful in CI pipelines.

Think about how Docker saves time by not repeating work.

Describe strategies to enable Docker layer caching in a CI environment.

Consider how to keep cache available between fresh CI runs.