To build Kubernetes you need to have access to a Docker installation through either of the following methods:
- Run on Mac OS X. The best way to go is to use
boot2docker. See instructions here. - Run on Linux against a local Docker. Install Docker according to the instructions for your OS. The scripts here assume that they are using a local Docker server and that they can "reach around" docker and grab results directly from the file system.
The scripts directly under build/ are used to build and test. They will ensure that the kube-build Docker image is built (based on build/build-image/Dockerfile) and then execute the appropriate command in that container. If necessary (for Mac OS X), the scripts will also copy results out.
The kube-build container image is built by first creating a "context" directory in output/build-image. It is done there instead of at the root of the Kubernetes repo to minimize the amount of data we need to package up when building the image.
Everything in build/build-image/ is meant to be run inside of the container. If it doesn't think it is running in the container it'll throw a warning. While you can run some of that stuff outside of the container, it wasn't built to do so.