Docker layer caching in CI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the base image in a Dockerfile.

Docker

FROM [1]

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

ARUN apt-get update

Bubuntu:20.04

CCOPY . /app

DCMD ["bash"]

Attempts:

3 left

💡 Hint

Common Mistakes

Using RUN or COPY instead of a base image after FROM.

Leaving FROM instruction empty.

The FROM instruction sets the base image for the Docker build. Here, ubuntu:20.04 is a valid base image.

2fill in blank

medium

Complete the GitHub Actions step to restore Docker cache using actions/cache.

Docker

- name: Restore Docker cache
  uses: actions/cache@v3
  with:
    path: /tmp/.buildx-cache
    key: ${{ runner.os }}-docker-[1]

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

Abuildx-cache

Bdockerfile

Ccache-key

Dimage-tag

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated strings like 'dockerfile' or 'image-tag' as cache keys.

Not including runner.os in the key for OS-specific caching.

The cache key should be unique to the build context. buildx-cache is commonly used to identify the Docker build cache.

3fill in blank

hard

Fix the error in the Docker build command to enable cache from a local directory.

Docker

docker buildx build --cache-from=type=local,src=[1] --cache-to=type=local,dest=/tmp/.buildx-cache .

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A/tmp/.buildx-cache

B/var/lib/docker

C/cache/buildx

D/home/user/cache

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated directories that do not contain the cache.

Mismatching cache-from and cache-to paths.

The --cache-from option should point to the directory where the cache was saved, here /tmp/.buildx-cache.

4fill in blank

hard

Fill both blanks to create a Docker build command that pushes the image and uses cache correctly.

Docker

docker buildx build --push --tag myimage:latest --cache-from=type=[1],src=/tmp/.buildx-cache --cache-to=type=[2],dest=/tmp/.buildx-cache .

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Alocal

Bregistry

Cinline

Dgha

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing different cache types for from and to options.

Using 'registry' or 'inline' when local caching is intended.

Using local for both --cache-from and --cache-to means the cache is stored and retrieved from a local directory.

5fill in blank

hard

Fill all three blanks to define a GitHub Actions job step that builds, caches, and pushes a Docker image.

Docker

- name: Build and push Docker image
  run: |
    docker buildx build \
    --tag myapp:latest \
    --cache-from=type=[1],src=/tmp/.buildx-cache \
    --cache-to=type=[2],dest=/tmp/.buildx-cache \
    --push .
  env:
    DOCKER_BUILDKIT: [3]

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

Alocal

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using different cache types for from and to.

Forgetting to enable BuildKit by setting DOCKER_BUILDKIT=1.

The cache types for from and to are both local. Setting DOCKER_BUILDKIT to 1 enables BuildKit, which supports advanced caching.