Check out the new Buildah project logo. Isn’t it sweet?

Getting Started with Buildah

I’ve been working with Linux containers at Red Hat since OpenShift used cartridges. With the help of some colleagues in Redwood City, I built a Red Hat MRG Messaging (Qpid) broker cartridge. When OpenShift moved to Docker, in 2013, I contributed all the original Docker man pages. I also got to contribute some of the original content to the Project Atomic web site (this site).

I’m very excited to see the Project Atomic efforts in the area of the Open Container Initiative (OCI) and specifically Buildah. After trying out the great work that the team have contributed, I discovered I had the start of a pretty useful introductory tutorial, and decided to see if I could contribute that content upstream. That pull request was merged recently. So let’s get started.

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Using Buildah with container registries

Prerequisite: Buildah version 0.9 or greater.

First some terminology. In the container image space, Docker popularized two terms:

• Container image registry
• Container image repository

The container image registry, or registry, is a shared data store for pushing and pulling container images. It has a well-known API for such requests. Docker Hub is an example of a public registry. Various vendors and developers store their images on Docker Hub. Most organizations I’ve dealt with don’t wish to pull images from a public registry for reasons such as security or network bandwidth usage. Instead they would prefer to use a local private registry.

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Building a Buildah Container Image for Kubernetes

Background

Dan Walsh (@rhatdan) asked me to look into building a working Buildah container image. This was not just a cool experiment. It has a real purpose. As many readers know, Dan is not a fan of big fat daemons. This has become less of an issue when running containers in Kubernetes as there is an alternative with CRI-O. CRI-O provides kubernetes a standard interface to OCI compliant runtimes. runC is the reference implementation of the OCI runtime specification. Kubernetes calls the runtC runtime through CRI-O and runC then talks to the Linux kernel to run a container. This bypasses the need for the Docker daemon, and containerd. With CRI-O, there is no requirement for the Docker daemon for a kubernetes cluster to run containers.

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