In most cases, your CI workflow should work fine with our official images which are used by default. However, you might want to consider using a custom Docker image in the following situations:
- Your build has dependencies that take a long time to install if installed as part of your CI workflow.
- You want to build a project written in a language not officially supported by Shippable.
- You are using a combination of languages and tools not supported together in any official images.
- You want to run CI in your own Docker image to better simulate your production environment.
This sample shows you how you can build a custom Docker image which can then be used to execute your CI workflow. The complete tutorial is at http://docs.shippable.com/ci/tutorial/build-custom-ci-image/