What is BuildKit in Docker: Features and Usage

BuildKit is a modern build engine for Docker that improves image building speed, efficiency, and flexibility. It enables features like parallel builds, caching, and better output control, making Docker builds faster and more reliable.

How It Works

Think of BuildKit as a smarter kitchen for cooking your Docker images. Instead of preparing one dish at a time, it can work on multiple parts of the recipe simultaneously, saving time. It breaks down the build process into smaller steps and runs them in parallel when possible.

BuildKit also remembers what it has cooked before, so if you make small changes, it only re-cooks the parts that changed. This caching saves a lot of time, especially for big projects. It also gives you better control over the build output, like showing progress in a clear way and allowing secrets or SSH keys to be used safely during the build.

Example

This example shows how to enable BuildKit and build a Docker image using it.

bash

export DOCKER_BUILDKIT=1

docker build -t myapp:latest .

Output

Sending build context to Docker daemon  2.56kB
Step 1/3 : FROM alpine:latest
 ---> a24bb4013296
Step 2/3 : RUN echo "Hello from BuildKit"
 ---> Running in 123abc456def
Hello from BuildKit
Removing intermediate container 123abc456def
 ---> 789xyz123uvw
Step 3/3 : CMD ["echo", "BuildKit is enabled"]
 ---> Running in 456def789abc
Removing intermediate container 456def789abc
 ---> 321uvw654rst
Successfully built 321uvw654rst
Successfully tagged myapp:latest

When to Use

Use BuildKit when you want faster and more efficient Docker image builds. It is especially helpful for large projects with many layers or when you need to build images frequently during development.

BuildKit is also useful when you want to use advanced features like build secrets (for private keys or passwords), SSH forwarding, or better caching strategies. It improves build reliability and can reduce build times significantly in continuous integration (CI) pipelines.

Key Points

• BuildKit speeds up Docker builds by running steps in parallel.
• It uses caching smartly to avoid repeating work.
• Supports advanced features like secrets and SSH forwarding during builds.
• Improves build output readability and control.
• Can be enabled by setting DOCKER_BUILDKIT=1 before building.

Key Takeaways

BuildKit is a faster, more efficient Docker build engine with advanced features.

Enable BuildKit by setting the environment variable DOCKER_BUILDKIT=1.

It improves build speed by running steps in parallel and using smart caching.

BuildKit supports secure use of secrets and SSH keys during image builds.

Ideal for large projects and CI pipelines to reduce build times and increase reliability.