7.3.3. Build Contexts

When building an image with Docker, a directory is specified to become the build context. This holds true for both manual builds and build triggers because the builds conducted by Red Hat Quay are no different from running docker build on your own machine.

Red Hat Quay build contexts are always the specified subdirectory from the build setup and fallback to the root of the build source if none is specified. When a build is triggered, Red Hat Quay build workers clone the git repository to the worker machine and enter the build context before conducting a build.

For builds based on tar archives, build workers extract the archive and enter the build context. For example:

example
├── .git
├── Dockerfile
├── file
└── subdir
    └── Dockerfile

example
├── .git
├── Dockerfile
├── file
└── subdir
    └── Dockerfile

Imagine the example above is the directory structure for a GitHub repository called "example". If no subdirectory is specified in the build trigger setup or while manually starting a build, the build will operate in the example directory.

If subdir is specified to be the subdirectory in the build trigger setup, only the Dockerfile within it is visible to the build. This means that you cannot use the ADD command in the Dockerfile to add file, because it is outside of the build context.

Unlike the Docker Hub, the Dockerfile is part of the build context on Red Hat Quay. Thus, it must not appear in the .dockerignore file.