docker / buildx

Multi-Platform Builds

Motivation: The buildx command enables you to build images for multiple architectures, simplifying the process of deploying to diverse environments. It accomplishes this by leveraging features like manifest lists, QEMU emulation, and cross-compilation.

Building Multi-Platform Images

The buildx command offers several options for building multi-platform images:

1. Using --platform Flag:

This option specifies the architecture and operating system you want to build for. You can specify multiple platforms using the --platform flag multiple times.

Example:

buildx build --platform linux/amd64 --platform linux/arm64 .

This command builds the image for both AMD64 and ARM64 architectures.

2. Using --output Flag:

The --output flag allows you to specify the output type. You can use type=manifest to generate a manifest list.

Example:

buildx build --output type=manifest .

This command builds a manifest list that contains images for all the supported platforms.

3. Using --push Flag:

You can directly push the built manifest list to a registry using the --push flag.

Example:

buildx build --push .

This command builds a manifest list and pushes it to the default registry.

4. Using QEMU Emulation:

buildx utilizes QEMU emulation to allow building images for architectures that your host machine doesn’t natively support.

Example:

buildx build --platform linux/arm64 --use qemu .

This command uses QEMU to emulate an ARM64 environment for building the image.

5. Building on Multiple Nodes:

You can use buildx to build images on multiple nodes by using the buildx create command to create a builder instance. This builder instance can then be used to distribute builds across multiple nodes.

Example:

buildx create --name multi-platform-builder --driver docker-container
          buildx use multi-platform-builder

This command creates a builder instance named multi-platform-builder and makes it the active builder. You can then use the buildx build command to build images on this instance.

6. Cross-Compiling with Dockerfile Stages:

Dockerfile stages allow you to build different parts of the image for different platforms using the --platform flag. This helps to optimize the build process by only rebuilding the necessary parts.

Example:

FROM golang:1.17-alpine AS builder
          RUN GOOS=linux GOARCH=arm64 go build -o myapp .
          
          FROM alpine:latest
          COPY --from=builder /myapp /myapp
          CMD ["/myapp"]

7. Exploring Dockerfile Cross-Compilation Helpers:

Libraries like tonistiigi/xx can simplify the process of cross-compiling within Dockerfiles.

Source of Information and Code Files: