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Kubernetes gobbles rkt for instant-on containers – no Docker required

Building 'Google-like' data centers now easier than ever

CoreOS Fest Cloudy Linux startup CoreOS kicked off its inaugural CoreOS Fest event in San Francisco on Monday with word that its homegrown rkt (pronounced "rocket") container runtime software will be integrated into the Google-derived Kubernetes container orchestration software.

What that means is that Kubernetes will be able to fire up Linux containers all on its own, without relying on the Docker Engine.

"The integration allows Kubernetes to invoke rkt to actually run the container as part of what Kubernetes does," CoreOS CEO Alex Polvi told The Register. "The net result is that the Kubernetes containers now launch rkt containers instead of Docker containers."

Polvi added that the option to run Docker with Kubernetes will still be there, if that's what you prefer. But once the integration with rkt is complete, it will no longer strictly be necessary. One of the features of rkt is that it can download Docker container images and convert them to its own format on the fly, eliminating the need for the additional Docker software.

CoreOS announced rkt and its accompanying App Container specification (appc) in December as a community-developed, standards-based alternative to Docker, which has rapidly risen to prominence as the de facto container technology for Linux.

CoreOS's core product, a lightweight Linux distro designed for hyper-scale cloud deployments, initially relied heavily on Docker for application deployment and management. But the CoreOS team eventually grew frustrated with what they saw as shortcomings of Docker's design – and its security model, in particular – and decided to create an alternative.

App Container gains industry support

The rkt software that resulted is an implementation of the App Container specification. On Monday, CoreOS welcomed the first three community maintainers for that spec, in the form of Google's Tim Hockins, Red Hat's Vincent Batts, and Twitter's Charles Aylward. The trio join CoreOS's own Brandon Philips and Jonathan Boulle, who had been maintaining the spec so far.

Polvi told El Reg that now that these outside maintainers have joined the appc specification effort, one of the goals of CoreOS's two-day event will be to raise awareness and discussion about the project's governance model.

"The project didn't exist four months ago," Polvi said. "So in the meantime we created code and then we created governance for that code and now the governance is actually coming into play, as we have outside maintainers. Because we have outside maintainers is the trigger to talk about it now."

In a canned statement, Batts, a senior Red Hat software engineer, said Shadowman sees containerization as the future of both Linux and software distribution.

"We see a joint responsibility for leaders in container technology to avoid past mistakes and drive toward a common standard, assuring freedom to innovate and consistent expectations," he said.

Google, meanwhile, has been cozying up to CoreOS of late. Its Google Ventures arm led the startup's recent $12m funding round, and CoreOS used Kubernetes as the basis of an enterprise offering called Tectonic, with some support from the Chocolate Factory. The fact that the Kubernetes team will now be returning the favor by integrating rkt only solidifies appc's position as a viable competitor in the Linux container market.

My competitor, my ally

Kubernetes isn't the only project that's taken an interest in rkt and appc. Also on Monday, Apcera, which markets what it calls its Hybrid Cloud Operating System, announced the launch of Kurma, a new container runtime that's based on the appc spec. And while Apcera's offering is a competitor to CoreOS and Kurma is essentially an analog to rkt, Polvi said that's fine with him.

"We're really showing that we have a standard, because there are alternative implementations that weren't written by us at all," he said. "It's not just a CoreOS thing, calling it a standard. We have other vendors now using the standard to build their own tools. And rkt and Kurma will be interoperable because we share App Container."

Apcera isn't the first company to get on board with the appc, either. Earlier this month, VMware announced that it would support rkt as one of the three container runtimes supported on its Project Photon micro-Linux distro, which itself is somewhat of a competitor to CoreOS.

Quay day

Finally, CoreOS used its event to announce upgrades to its Quay hosted container repository service, an alternative to Docker Hub. The improvements are mostly spit n' polish, including a revamped UI and a new caching layer that speeds up builds, but there are some new features, as well.

A feature called "time machine" allows Quay users to roll back their repositories to an earlier state in the event that pushing a new image causes problems, and it maintains a record of past states for up to two weeks. Also, Quay now features support for Git submodiles, Bitbucket, and GitLab.

"Quay is a key offering from CoreOS and we will continue to invest heavily in the container registry as both a standalone product and as a feature of Tectonic," Polvi said. ®

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