Book Image

Learning CoreOS

By : Kingston Smiler. S, Shantanu Agrawal
Book Image

Learning CoreOS

By: Kingston Smiler. S, Shantanu Agrawal

Overview of this book

CoreOS is an open source operating system developed upon the Linux kernel. The rise of CoreOS is directly related to the rise of Docker (a Linux container management system). It is a minimal operating system layer and takes a different approach to automating the deployment of containers. The major difference between CoreOS and other Linux distributions is that CoreOS was designed to deploy hundreds of servers. CoreOS immensely helps the users to create systems, which are easy to scale and manage, making life easier for all, be it developer, QA, or deployer. This book is all about setting up, deploying, and using CoreOS to manage clusters and clouds. It will help you understand what CoreOS is and its benefits as a cloud orchestration platform. First, we’ll show you how to set up a simple CoreOS instance with single node in the cluster and how to run a Docker container inside the CoreOS instance. Next, you’ll be introduced to Fleet and systemd, and will deploy and distribute Docker services across different nodes in cluster using Fleet. Later, you’ll be briefed about running services in a cluster with constraints, publishing the services already running on the cluster to new services, and making your services interact with each other. We conclude by teaching you about advanced container networking. By the end of the book, you will know the salient features of CoreOS and will be able to deploy, administrate, and secure a CoreOS environment.
Table of Contents (15 chapters)
Learning CoreOS
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Introduction to Weave


We learned before that applications running inside Docker have no knowledge of the IP address of the host machine. Hence, they are not in position to register their IP for the service, since another container running outside the host has to use the host IP address for accessing the service.

If an IP address of the host machine is passed as an environment variable, service information can be stored in etcd and read by the service user as illustrated in Chapter 5, Discovering Services Running in Cluster. This approach requires the application code to be aware of how services can be discovered.

Weave simplifies service discovery and does a lot more. Weave provides a mechanism to connect applications running inside a Docker container irrespective of where they are deployed. Since application services are running as a Docker container, the ease of communication of micro-services running in Docker containers is very important.

Weave registers the named containers automatically...