CoreOS was built in 2013, for the internet; focusing on making it reliable and secure. Its focus was for developers/companies to run their applications without worrying about security.
It was acquired in 2018 by RedHat, for application services in the hybrid cloud. Combined with Red Hat OpenShift, it will power the Linux Container platform stack, using its automation technologies.
The development of some of the new open source tools, that are becoming parts and parcels of present-day cloud computing systems, is the focus of the Red Hat team for CoreOS. Some of these are Prometheus (container monitoring system), Kubernetes (container orchestrator), Container Linux (lightweight container-centric OS), etcd(distributed key-value store).
The coreOS is organized using a building block architecture, the first building block, etcd, helping service discovery and the second building block, docker, for container management.
Service discovery in CoreOs containers is made possible through etcd. Such that data is circulated throughout your clusters running Linux containers. Making it possible for each container within the cluster to announce its existence to all neighboring containers. For automatic data packet routing to containers, within the cluster. This first and really crucial building block makes the incremental addition of machines to your etcd cluster possible. Helping it scale seamlessly.
Container management in CoreOS is made possible, through Docker. Within it, all your code and applications have their run time environment. Through Docker, your separate services such as database, HTTP server and caching are organized into containers. With their read and write processes connected with etcd.