The Open Container Initiative (OCI), a Linux Foundation Project, has finally decided to address one of the biggest criticisms of Docker containers -- lack of an open, standard container image format. In response to market demands, OCI has created a container image format specification project to create standard specs. The project is hosted on GitHub.

It’s a positive outcome of the pressure CoreOS has been putting on Docker and OCI to address issues like security, naming and an open image format. Docker's reluctance to address these issues lead CoreOS to come out with their own solutions -- rkt ("rocket"), an alternative of Docker and App Container (appc) specs.

The reluctance from OCI can be attributed to the fact that the body was formed recently and they wanted to keep a very narrow focus on their goal. But major players like VMWare, Google and Red Hat backed rkt by CoreOS, sending out a very a strong message. These heavyweight are also members of OCI, so their support for rkt and appc carried a lot of weight.

Eventually, OCI decided to expand its focus. CoreOS praised the move by OCI and wrote in a blog post, “Today the OCI’s focus has broadened to include a new OCI Image Format Spec, an open specification for a container image, the build artifact that contains everything needed to run a piece of software”

OCI will use Version 2.2 of Docker image as the base for specs development. This image format has already included many features that CoreOS developed for their own appc spec project.

The main goal of the Container Image Format specs project is to create a software shipping container image format spec (OCI Image Format) with security and naming as components. The OCI Image Format specs project has set four primary objectives for itself:

A serialized image format (base layer)

A process of hashing the image format for integrity and content-addressing (base layer)

Signatures that are based on signing image content address (optional layer)

Naming that is federated based on DNS and can be delegated (optional layer)

OCI’s Image Format specs project includes members from various stakeholders of the container technology, including Vincent Batts, Red Hat (TOB member); Jonathan Boulle, CoreOS; Jason Bouzane, Google (TOB member); Brendan Burns, Google; Stephen Day, Docker; Brandon Philips, CoreOS; and John Starks, Microsoft. Additionally, TOB members include: Michael Crosby, Docker; Pavel Emelyanov, Virtuozzo; John Gossman, Microsoft; Greg Kroah-Hartman, The Linux Foundation; Dr. Diogo Monica, Docker; and Chris Wright, Red Hat.

According to the roadmap of the Container Image Format specs project, the initial version of the project is expected to be released by June.

“We hope the OCI image format quickly becomes the single shared industry standard that all future build, storage, and runtime products employ,” said Jonathan Boulle of CoreOS in a blog post.