BuildKit for improved builds in Docker - Commands & Configuration

Introduction

Building Docker images can be slow and inefficient. BuildKit is a modern builder that speeds up builds, reduces image size, and improves caching to save time and resources.

When you want faster Docker image builds for your application.

When you need to use advanced caching to avoid rebuilding unchanged parts.

When you want to build multi-stage Dockerfiles more efficiently.

When you want better output logs that are easier to read.

When you want to build images with secrets or SSH keys safely.

Commands

This command enables BuildKit for your Docker client session to improve build performance and features.

Terminal

export DOCKER_BUILDKIT=1

Expected Output

No output (command runs silently)

Builds the Docker image named 'my-app' using BuildKit, which is enabled by the environment variable set earlier.

Terminal

docker build -t my-app:latest .

Expected Output

#1 [internal] load build definition from Dockerfile

#1 sha256:abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890

#1 transferring dockerfile: 123B done

#1 DONE 0.1s



#2 [internal] load .dockerignore

#2 sha256:123456abcdef123456abcdef123456abcdef123456abcdef123456abcdef123456

#2 transferring context: 2B done

#2 DONE 0.1s



#3 [internal] load metadata for docker.io/library/python:3.10-slim

#3 sha256:abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef

#3 DONE 1.2s



#4 [1/5] FROM docker.io/library/python:3.10-slim@sha256:abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef

#4 DONE 0.0s



#5 [2/5] WORKDIR /app

#5 DONE 0.0s



#6 [3/5] COPY requirements.txt ./

#6 DONE 0.0s



#7 [4/5] RUN pip install -r requirements.txt

#7 DONE 3.5s



#8 [5/5] COPY . .

#8 DONE 0.1s



#9 exporting to image

#9 sha256:abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef

#9 exporting layers

#9 writing image sha256:abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef done

#9 naming to docker.io/library/my-app:latest done



Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them

→

-t - Assigns a name and optionally a tag to the image

Lists the available BuildKit builder instances to verify BuildKit is active and see builder details.

Terminal

docker buildx ls

Expected Output

NAME/NODE       DRIVER/ENDPOINT             STATUS  PLATFORMS

default *       docker-container           running linux/amd64, linux/arm64, linux/arm/v7

Key Concept

If you remember nothing else from this pattern, remember: enabling BuildKit speeds up Docker builds and improves caching automatically.

Common Mistakes

Not enabling BuildKit before running docker build.

Docker uses the older builder by default, missing out on speed and caching improvements.

Run 'export DOCKER_BUILDKIT=1' in your terminal before building images.

Using outdated Docker versions that do not support BuildKit.

BuildKit requires Docker 18.09 or newer to work properly.

Update Docker to the latest stable version to use BuildKit features.

Summary

Enable BuildKit by setting the environment variable DOCKER_BUILDKIT=1.

Build images with 'docker build' to get faster builds and better caching.

Use 'docker buildx ls' to check active BuildKit builders and platforms.