CoreOS 'Rockets' Ahead With Docker Alternative

By Sean Michael Kerner  |  Posted 2015-02-01 Print this article Print
CoreOS container virtualization

Linux operating system distribution vendor CoreOS aims to expand its own vision for container-based virtualization.

CoreOS is moving forward on its plans to displace the Docker application virtualization technology and expand its own vision for container-based virtualization. CoreOS got its start in 2013 as a clustered operating system project focused on the optimized delivery of Docker containers but has found fault in the Docker model that it aims to correct with its own Rocket approach.

A key part of the CoreOS platform is the etcd system, which provides a shared configuration and scheduler coordination capability that is enabled by a distributed, consistent key-value store. As an open-source effort led by CoreOS, etcd is also used in the Google Kubernetes project as well as Pivotal's Cloud Foundry and Apache Mesos.

On Jan. 28, CoreOS announced etcd version 2.0 and tagged it as the first major stable release of the technology. Prior to etcd 2.0, the most recent version was 0.4.6.

The decision was made to call the new release 2.0 because applications were using etcd code against  what was referred to as the etcd v2 API, Brandon Philips, CoreOS CTO, explained.

"We decided it was better to make our first stable release 2.0 to keep the API version and release versions in sync," Philips told eWEEK. "With over a year and a half of work on etcd, combined with lots of help from the more than 150 developers in the etcd community, etcd 2.0 marks a culmination of development toward a more stable and useful project."

Though etcd development is led by CoreOS developers, Philips noted that etcd is developed as its own open-source project with its own community.  He pointed out that etcd has both Microsoft Windows and Mac OS X builds and can run on other Linux systems such as Debian or Fedora.

The etcd 2.0 release includes improvements designed to guard against accidental misconfiguration. "The big safety features we added were unique IDs to the internal protocol to identify cluster members and clusters," Philips explained.

By adding the unique IDs, there is less risk of virtual machine cloning causing two machines to confuse the cluster, or old cluster members being removed and re-added with stale data from backups.

"We also added a number of nice command line tools and APIs to manage reconfiguring the cluster after machine failures and safely backing up and restoring data from etcd," Philips said. "We made a huge number of improvements to make these sorts of operations safer and easier."

The Rocket Effort

CoreOS first announced the Rocket effort in December 2014, along with the associated App Container Specification technically referred to as appc. With Rocket and appc, the goal is to develop a standard unit for a container in the same way that an Amazon Machine Image (AMI) is a basic unit of deployment for the Amazon Elastic Cloud Compute (EC2) public cloud.

Development is progressing rapidly with new releases of appc and Rocker every few weeks. The most recent update for Rocket was version 0.2.0, which debuted Jan. 23. The Rocket 0.2.0 update incorporates an automatic signature validation feature.

"We want to push this idea that, by default, containers should not run unless the author has signed the code and the user trusts the author," Philips explained. "Securing the back-end Internet is our goal with CoreOS and code signing and signature validation is part of that."


The open-source Docker project, which is still used by CoreOS in its production builds, on Jan. 28 announced several moves to open up its development process. Though the Docker project is trying to improve its development process, CoreOS still has some concerns.

"Our primary concern is that we want the container to be a standard composable unit, which is why we introduced the App Container (appc) spec," Philips said. "Docker is growing to be a platform, which is great, but it isn't the container it set out to be."

While CoreOS doesn't currently see eye-to-eye with Docker, there is potential for detente.

"We would love to work together with Docker to help define the appc spec and ensure that as an industry we are making this composable independent building block of infrastructure," Philips said.

Sean Michael Kerner is a senior editor at eWEEK and Follow him on Twitter @TechJournalist.

 Editor's note: This story was updated to state that the CoreOS Rocket project started in 2014.


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