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App Container and the Open Container Project

Today we’re pleased to announce that CoreOS, Docker, and a large group of industry leaders are working together on a standard container format through the formation of the Open Container Project (OCP). OCP is housed under the Linux Foundation, and is chartered to establish common standards for software containers. This announcement means we are starting to see the concepts behind the App Container spec and Docker converge. This is a win for both users of containers and our industry at large.

In December 2014 we announced rkt, a new container runtime intended to address issues around security and composability in the container ecosystem. At the same time, we started App Container (appc), a specification defining a container image format, runtime environment and discovery protocol, to work towards the goal of a standard, portable shipping container for applications. We believe strongly that open standards are key to the success of the container ecosystem.

We created App Container to kickstart a movement toward a shared industry standard. With the announcement of the Open Container Project, Docker is showing the world that they are similarly committed to open standards. Today Docker is the de facto image format for containers, and therefore is a good place to start from in working towards a standard. We look forward to working with Docker, Google, Red Hat and many others in this effort to bring together the best ideas across the industry.

As we participate in OCP, our primary goals are as follows:

  • Users should be able to package their application once and have it work with any container runtime (like Docker, rkt, Kurma, or Jetpack)
  • The standard should fulfill the requirements of the most rigorous security and production environments
  • The standard should be vendor neutral and developed in the open

App Container

We believe most of the core concepts from App Container will form an important part of OCP. Our experience developing App Container will play a critical role as we begin collaboration on the OCP specification. We anticipate that much of App Container will be directly integrated into the OCP specification, with tweaks being made to provide greater compatibility with the existing Docker ecosystem. The end goal is to converge on a single unified specification of a standard container format, and the success of OCP will mean the major goals of App Container are satisfied. Existing appc maintainers Brandon Philips and Vincent Batts will be two of the initial maintainers of OCP and will work to harmonize the needs of both communities in the spirit of a combined standard. At the same time we will work hard to ensure that users of appc will have a smooth migration to the new standard.

Continuing work on rkt

CoreOS remains committed to the rkt project and will continue to invest in its development. Today rkt is a leading implementation of appc, and we plan on it becoming a leading implementation of OCP. Open standards only work if there are multiple implementations of the specification, and we will develop rkt into a leading container runtime around the new shared container format. Our goals for rkt are unchanged: a focus on security and composability for the most demanding production environments.

We are excited the industry is converging a format that combines the best ideas from appc, rkt and Docker to achieve what we all need to succeed: a well-defined shared standard for containers.

For more information and to see the draft charter and founding formation of the OCP, go to