Over the past two years, containerization technology has had a tremendous growth in popularity. While Docker has been at the center of this ecosystem, there is an increasing number of players in the container space. There are already a number of alternatives to the containerization and Docker implementation itself (rkt, Garden, and so on). In addition, there is a rich ecosystem of third-party tools that enhance and complement your container infrastructure. While Kubernetes is designed to manage the state of a container and the orchestration, scheduling, and networking side of this ecosystem, the bottom line is that all of these tools form the basis to build cloud-native applications.

As we mentioned at the very beginning of this book, one of the most attractive things about containers is their ability to package our application for deployment across various environment tiers (that is, development, testing, and production) and various infrastructure providers (GCP, AWS, on-premises, and so on).

To truly support this type of deployment agility, we need not only the containers themselves to have a common platform, but also the underlying specifications to follow a common set of ground rules. This will allow for implementations that are both flexible and highly specialized. For example, some workloads may need to be run on a highly secure implementation. To provide this, the implementation will have to make more intentional decisions about some aspects of the implementation. In either case, we will have more agility and freedom if our containers are built on some common structures that all implementations agree on and support.

In the following pages, we'll explore the building blocks of the many competing standards in the Kubernetes ecosystem. We'll explain how they're changing and developing and what part they may play in the future.

One of the examples that we'll explore more deeply in this third edition is the CRI-O project, which came to be after the creation of the OCI Charter. Let's make sure we understand the importance of that mission.