Docker as a Build Environment in CI/CD

There are several uses for Docker at this stage of development, even if you don't end up packaging your application as a container image. ## Docker as a build environment Containers are reproducible, isolated environments that yield predictable results. Building and testing your application in a Docker container makes it easier to prevent unexpected behaviors from occurring. Using a Dockerfile, you define the exact requirements for the build environment, including programming runtimes, operating system, binaries, and more. Using Docker to manage your build environment also eases maintenance. For example, updating to a new version of a programming runtime can be as simple as changing a tag or digest in a Dockerfile. No need to SSH into a pet VM to manually reinstall a newer version and update the related configuration files. Additionally, just as you expect third-party open source packages to be secure, the same should go for your build environment. You can scan and index a builder image, just like you would for any other containerized application. The following links provide instructions for how you can get started using Docker for building your applications in CI: - [GitHub Actions](https://docs.github.com/en/actions/creating-actions/creating-a-docker-container-action) - [GitLab](https://docs.gitlab.com/runner/executors/docker.html) - [Circle CI](https://circleci.com/docs/using-docker/) - [Render](https://render.com/docs/docker) ### Docker in Docker You can also use a Dockerized build environment to build container images using Docker. That is, your build environment runs inside a container which itself is equipped to run Docker builds. This method is referred to as "Docker in Docker". Docker provides an official [Docker image](https://hub.docker.com/_/docker) that you can use for this purpose. ## What's next Docker maintains a set of official GitHub Actions that you can use to build, annotate, and push container images on the GitHub Actions platform. See [Introduction to GitHub Actions](github-actions/_index.md) to learn more and get started.

This section details the benefits of using Docker as a build environment in continuous integration, emphasizing reproducibility, isolation, and predictable results. It explains how Dockerfiles allow defining precise build requirements, easing maintenance, and enhancing security by enabling the scanning and indexing of builder images. The passage also highlights the 'Docker in Docker' approach for building container images within a Dockerized build environment and suggests official Docker images for this purpose. It concludes by pointing to Docker's official GitHub Actions for building, annotating, and pushing container images on the GitHub Actions platform, directing the reader to an introduction on GitHub Actions for more information.