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Multi stage builds

Multi-Stage Builds


Multi Stage builds were introduced in Docker 17.05, allowing you to optimize your image builds and share data between different builds.

The ocibuilder allows you to easily define build stages in your specification in order to run a multi-stage build with either Docker or Buildah as the container builder.

Defining a multi-stage build

Multi-stage builds can defined at any build step. Each stage has a name defined under it's metadata field which can be referred to at any following build stage.

For example a simple multi-stage go build can look as follows:

- metadata:
    name: artbegolli/go-service
    - metadata:
        name: go-binary
        image: golang
        platform: alpine
        - docker:
              - ADD . /src
              - RUN cd /src && go build -o goapp
    - metadata:
        name: alpine-stage
        image: alpine
        - docker:
              - WORKDIR /app
              - COPY --from=go-binary /src/goapp /app/
              - ENTRYPOINT ./goapp

The first stage of the build uses the golang:alpine base image to build our go binary and is named go-binary.

Our second build stage refers to just our binary built in the first stage with --from=go-binary and copies this into our new container image and sets an entrypoint.

This ultimately results in a significantly smaller image size by creating a minimal image which just contains our build artifcat.

Future Enhancements

  • Context labels defined for each stage

Docker Multi-Stage Builds