rkt

"rkt is the next-generation container manager for Linux clusters. Designed for security, simplicity, and composability within modern cluster architectures, rkt discovers, verifies, fetches, and executes application containers with pluggable isolation. rkt can run the same container with varying degrees of protection, from lightweight, OS-level namespace and capabilities isolation to heavier, VM-level hardware virtualization.

rkt’s primary interface comprises a single executable, rather than a background daemon, and rkt leverages this design to easily integrate with existing init systems, like systemd, and with advanced cluster orchestration environments, like Kubernetes. rkt implements a modern, open, standard container format, the App Container (appc), but can also execute other container images, like those created with Docker.

rkt is open source software written in the Go programming language, from the team that develops CoreOS Linux, etcd, flannel, and dozens of other projects for enterprise container clusters.

Some of rkt's key features and goals include:

• Pod-native: rkt's basic unit of execution is a pod, linking together resources and user applications in a self-contained environment.
• Security: rkt is developed with a principle of "secure-by-default", and includes a number of important security features like support for SELinux, TPM measurement, and running app containers in hardware-isolated VMs.
• Composability: rkt is designed for first-class integration with init systems (like systemd, upstart) and cluster orchestration tools (like Kubernetes and Nomad), and supports swappable execution engines.
• Open standards and compatibility: rkt implements the appc specification, supports the Container Networking Interface specification, and can run Docker images and OCI images. Broader native support for OCI images and runtimes is in development.

The rkt v1.x series provides command line user interface and on-disk data structures stability for external development. Any major changes to those primary areas will be clearly communicated, and a formal deprecation process conducted for any retired features.

Check out the roadmap for more details on the future of rkt.

To get started quickly using rkt for the first time, start with the "trying out rkt" document. Also check rkt support on your Linux distribution. For an end-to-end example of building an application from scratch and running it with rkt, check out the getting started guide."

https://coreos.com/rkt/

https://medium.com/@adriaandejonge/moving-from-docker-to-rkt-310dc9aec938