CoreOS launches Rocket, a Docker alternative

CoreOS Inc., the Linux operating system services company, announced Rocket, its new command line tool for running app containers. The company released a prototype version on GitHub to begin gathering feedback from the open source community.

App containers, created by Docker in 2013, give developers a simpler way to build, ship and run distributed applications. The Docker platform consists of the Docker Engine, a portable, lightweight runtime and packaging tool, and Docker Hub, a cloud service for sharing applications and automating workflows.

With Docker, developers can build any app in any language and be sure they’ll run on any platform.

However,  according to CoreOS CEO and co-founder Alex Polvi on the Core Blog, Docker has now morphed from a “composable building block” to a complex platform that includes tools for launching cloud servers, systems for clustering and a wide range of functions that are “all compiled into one monolithic binary running primarily as root on your server.”

Polvi said he still supports Docker’s original premise for containers, but thinks Docker is moving away from the simple composable building block first envisioned.

CoreOS has built a new container format, called App Container, the company’s back-to-basics specification of an image format, container runtime and discovery mechanism. Rocket itself is a command line tool, rkt, for running App Containers.

CoreOS, a top Docker contributor, said it will continue contributing to the Docker open-source project, even as it continues work on Rocket. 

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