BuildKit for improved builds in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is BuildKit in Docker?

BuildKit is a modern build engine for Docker that improves build speed, efficiency, and adds new features like better caching and parallel build steps.

beginner

How do you enable BuildKit when running a Docker build?

You enable BuildKit by setting the environment variable DOCKER_BUILDKIT=1 before running the docker build command.

intermediate

Name one key advantage of using BuildKit over the traditional Docker build engine.

BuildKit supports parallel build steps, which means it can build different parts of the image at the same time, making builds faster.

intermediate

What is a practical way BuildKit improves caching during Docker builds?

BuildKit uses smarter caching that can reuse parts of previous builds even if some steps change, reducing the time needed for rebuilds.

advanced

How can BuildKit help with multi-platform Docker images?

BuildKit can build images for multiple platforms (like Linux and Windows) in one command, simplifying cross-platform builds.

How do you activate BuildKit for a Docker build?

A Use --enable-buildkit flag in docker build

B Set DOCKER_BUILDKIT=1 environment variable

C Install a separate BuildKit package

D BuildKit is enabled by default, no action needed

You enable BuildKit by setting the environment variable DOCKER_BUILDKIT=1 before running docker build.

What is one benefit of BuildKit's parallel build steps?

A It speeds up the build by running steps simultaneously

B It allows building multiple images at once

C It reduces the size of the final image

D It automatically updates Docker to the latest version

BuildKit speeds up builds by running independent build steps in parallel.

Which feature helps BuildKit reuse parts of previous builds?

A Layer squashing

B Automatic tagging

C Image compression

D Smarter caching

BuildKit uses smarter caching to reuse unchanged parts of previous builds.

BuildKit can build images for multiple platforms in one command. Which platforms are commonly supported?

A FreeBSD and AIX

B Android and iOS

C Linux and Windows

D MacOS and Solaris

BuildKit supports building images for Linux and Windows platforms.

What is the default build engine in Docker if BuildKit is not enabled?

A Legacy builder

B Kaniko

C BuildKit

D Docker Compose

Without enabling BuildKit, Docker uses the legacy builder engine.

Explain how BuildKit improves Docker build performance and caching.

Think about how BuildKit runs tasks and reuses previous work.

Describe the steps to enable and use BuildKit in a Docker build process.

Focus on environment setup and command usage.

Practice

1. What is the main purpose of enabling BuildKit in Docker builds?

easy

A. To speed up builds and provide smarter build features

B. To disable caching during Docker builds

C. To automatically push images to Docker Hub

D. To run containers in debug mode

Solution

1. Step 1: Understand BuildKit's role

   BuildKit is designed to improve Docker build speed and add smarter features like better caching and parallel steps.

2. Step 2: Compare options

   Options A, C, and D describe unrelated Docker features. Only To speed up builds and provide smarter build features correctly describes BuildKit's purpose.

3. Final Answer:

   To speed up builds and provide smarter build features -> Option A

4. Quick Check:

   BuildKit purpose = speed and smart builds [OK]

Hint: BuildKit improves build speed and features, not disables or pushes [OK]

Common Mistakes:

• Thinking BuildKit disables cache
• Confusing BuildKit with image pushing
• Assuming BuildKit runs containers

2. Which command correctly enables BuildKit for a Docker build?

easy

A. docker build --enable-buildkit .

B. docker build --buildkit=enable .

C. docker build -buildkit 1 .

D. DOCKER_BUILDKIT=1 docker build .

Solution

1. Step 1: Recall how to enable BuildKit

   BuildKit is enabled by setting the environment variable DOCKER_BUILDKIT=1 before running the docker build command.

2. Step 2: Analyze options

   Only DOCKER_BUILDKIT=1 docker build . uses the correct environment variable syntax. Options B, C, and D use invalid flags or syntax.

3. Final Answer:

   DOCKER_BUILDKIT=1 docker build . -> Option D

4. Quick Check:

   Enable BuildKit with env var DOCKER_BUILDKIT=1 [OK]

Hint: Set DOCKER_BUILDKIT=1 before docker build command [OK]

Common Mistakes:

• Using invalid flags like --buildkit=enable
• Trying to pass BuildKit as a docker build option
• Forgetting to set environment variable

3. What output difference will you see when running DOCKER_BUILDKIT=1 docker build . compared to a normal build?

medium

A. More detailed and clearer build step output

B. No output is shown during the build

C. Build output is shown in JSON format only

D. Build output is slower and less informative

Solution

1. Step 1: Understand BuildKit output changes

   BuildKit provides clearer, more detailed output with progress bars and parallel step info.

2. Step 2: Compare output options

   More detailed and clearer build step output matches this behavior. Options B and D are incorrect because output is shown and faster. Build output is shown in JSON format only is wrong because JSON output is not default.

3. Final Answer:

   More detailed and clearer build step output -> Option A

4. Quick Check:

   BuildKit output = clearer and detailed [OK]

Hint: BuildKit shows clearer, detailed build progress output [OK]

Common Mistakes:

• Expecting no output during build
• Thinking output is JSON by default
• Assuming BuildKit slows down output

4. You tried to enable BuildKit with docker build --buildkit=1 . but it failed. What is the likely cause?

medium

A. BuildKit is not supported on your Docker version

B. The flag --buildkit=1 is invalid; BuildKit must be enabled via environment variable

C. You need to add --enable-buildkit flag instead

D. You must run docker build as root to enable BuildKit

Solution

1. Step 1: Check how BuildKit is enabled

   BuildKit is enabled by setting the environment variable DOCKER_BUILDKIT=1, not by a docker build flag.

2. Step 2: Analyze the error cause

   Using --buildkit=1 is invalid syntax, causing the failure. Options B, C, and D are incorrect because BuildKit is supported in recent Docker versions, no such flag exists, and root is not required.

3. Final Answer:

   The flag --buildkit=1 is invalid; BuildKit must be enabled via environment variable -> Option B

4. Quick Check:

   BuildKit enabled only by env var, not flags [OK]

Hint: BuildKit enabled only by DOCKER_BUILDKIT=1 env var [OK]

Common Mistakes:

• Trying to enable BuildKit with invalid flags
• Assuming root permission is needed
• Believing BuildKit is disabled on all Docker versions

5. You want to speed up your Docker build by using BuildKit and also use a cache from a previous build stored locally. Which command correctly achieves this?

hard

A. docker build --cache-from=type=local,src=/path/to/cache .

B. docker build --buildkit=1 --cache-from=local:/path/to/cache .

C. DOCKER_BUILDKIT=1 docker build --cache-from=type=local,src=/path/to/cache .

D. DOCKER_BUILDKIT=1 docker build --cache-from=local:/path/to/cache .

Solution

1. Step 1: Enable BuildKit correctly

   BuildKit must be enabled by setting DOCKER_BUILDKIT=1 environment variable before the docker build command.

2. Step 2: Use correct cache-from syntax

   BuildKit supports advanced cache-from syntax like --cache-from=type=local,src=path. DOCKER_BUILDKIT=1 docker build --cache-from=type=local,src=/path/to/cache . uses this correctly. Options B and C use invalid flags or syntax. docker build --cache-from=type=local,src=/path/to/cache . misses enabling BuildKit.

3. Final Answer:

   DOCKER_BUILDKIT=1 docker build --cache-from=type=local,src=/path/to/cache . -> Option C

4. Quick Check:

   Enable BuildKit + correct cache-from syntax = DOCKER_BUILDKIT=1 docker build --cache-from=type=local,src=/path/to/cache . [OK]

Hint: Set DOCKER_BUILDKIT=1 and use --cache-from=type=local,src=path [OK]

Common Mistakes:

• Using --buildkit=1 flag instead of env var
• Incorrect cache-from syntax
• Forgetting to enable BuildKit