Build Dockerfile Build Kit

  Docker BuildKit is a modern build subsystem introduced by Docker to improve the efficiency and performance of building Docker images. It ...

 Docker BuildKit is a modern build subsystem introduced by Docker to improve the efficiency and performance of building Docker images. It provides features like caching, parallel execution, and advanced build syntax that helps speed up the process of creating Docker images.

To build a Docker image using BuildKit, follow these steps:

Step 1: Enable Docker BuildKit

Docker BuildKit is not enabled by default on older Docker versions, but it can be enabled manually in Docker 18.09 and later.

Option 1: Enable BuildKit via Environment Variable (temporary)

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

export DOCKER_BUILDKIT=1

Then, run the build command as usual:

docker build -t <image_name> .

Option 2: Enable BuildKit via Docker Configuration (permanent)

You can enable BuildKit permanently by modifying Docker’s configuration file.

1. Edit the Docker configuration file, typically located at /etc/docker/daemon.json.

2. Add the following JSON configuration:

{

  "features": {

    "buildkit": true

  }

}

Restart the Docker service to apply the changes:

 
sudo systemctl restart docker
Step 2: Build Docker Image Using BuildKit
Once BuildKit is enabled, you can use the docker build command to build images. BuildKit provides several additional features and options to enhance the build process.
Example Command:
DOCKER_BUILDKIT=1 docker build -t <image_name> .
Step 3: Use Advanced Dockerfile Features with BuildKit
BuildKit supports several advanced features that are not available in the traditional Docker build system. These include:
1. Multi-Stage Builds
Multi-stage builds allow you to create intermediate images that are discarded after the final image is created. This is useful to keep the final image smaller by excluding unnecessary build dependencies.
Example Dockerfile with Multi-Stage Build:
   
# Stage 1: Build
FROM node:16 AS build
WORKDIR /app
COPY . .
RUN npm install && npm run build

# Stage 2: Final image
FROM nginx:alpine
COPY --from=build /app/build /usr/share/nginx/html
In this example:
The first stage (build) compiles the app.
The second stage copies only the built app from the build stage to the final image.
2. Cache Import and Export
With BuildKit, you can specify cache import and export strategies, which allows sharing build cache across builds to speed up the process.
Example Dockerfile with Cache Export:

      
# Use a specific build cache from another build
RUN --mount=type=cache,source=/tmp/cache,target=/tmp/cache \
    some_command_to_use_cache

 The --mount=type=cache option allows for caching specific directories and using them between builds, thus avoiding redundant operations.
3. BuildKit Inline Secrets and SSH
BuildKit provides secure ways to pass secrets and SSH keys into the build process without exposing them in the image layers or Dockerfile.
Example Dockerfile with Secrets:
RUN --mount=type=secret,id=my_secret_file some_command
This way, you can securely provide secrets during the build process without exposing them in the Docker image.

 

4. Parallel Builds

BuildKit can execute independent build steps in parallel, which speeds up the build process. For example, multiple stages in the Dockerfile that do not depend on each other can be built in parallel.

Step 4: Build the Docker Image with BuildKit

Once you've configured your Dockerfile with BuildKit features, run the build command:

DOCKER_BUILDKIT=1 docker build -t <image_name> .

If you've enabled BuildKit permanently, you can omit the DOCKER_BUILDKIT=1 environment variable:

docker build -t <image_name> .
Step 5: Use Docker BuildKit Output
BuildKit can generate more structured output than the traditional Docker build system. You can use --progress to customize the output.
For example, to see detailed output during the build:

DOCKER_BUILDKIT=1 docker build --progress=plain -t <image_name> .
You can choose different progress formats:
plain (simple, detailed output)
tty (default, with interactive updates)
json (machine-readable output)
Conclusion
With Docker BuildKit, you can improve the efficiency, performance, and flexibility of your image builds. Key features like multi-stage builds, cache management, inline secrets, and parallel execution help streamline the Docker image build process. Enabling BuildKit can significantly reduce build times and make your builds more efficient, especially for large and complex projects.