Book Image

Learn Docker - Fundamentals of Docker 18.x

By : Dr. Gabriel N. Schenker
Book Image

Learn Docker - Fundamentals of Docker 18.x

By: Dr. Gabriel N. Schenker

Overview of this book

Docker containers have revolutionized the software supply chain in small and big enterprises. Never before has a new technology so rapidly penetrated the top 500 enterprises worldwide. Companies that embrace containers and containerize their traditional mission-critical applications have reported savings of at least 50% in total maintenance cost and a reduction of 90% (or more) of the time required to deploy new versions of those applications. Furthermore they are benefitting from increased security just by using containers as opposed to running applications outside containers. This book starts from scratch, introducing you to Docker fundamentals and setting up an environment to work with it. Then we delve into concepts such as Docker containers, Docker images, Docker Compose, and so on. We will also cover the concepts of deployment, orchestration, networking, and security. Furthermore, we explain Docker functionalities on public clouds such as AWS. By the end of this book, you will have hands-on experience working with Docker containers and orchestrators such as SwarmKit and Kubernetes.
Table of Contents (21 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Pods


Contrary to what is possible in a Docker Swarm, you cannot run containers directly in a Kubernetes cluster. In a Kubernetes cluster, you can only run pods. Pods are the atomic unit of deployment in Kubernetes. A pod is an abstraction of one or many co-located containers that share the same Kernel namespaces, such as the network namespace. No equivalent exists in the Docker SwarmKit. The fact that more than one container can be co-located and sharing the same network namespace is a very powerful concept. The following diagram illustrates two pods:

Kubernetes pods

In the preceding diagram, we have two pods, Pod 1 and Pod 2. The first pod contains two containers, while the second one only contains a single container. Each pod gets an IP address assigned by Kubernetes that is unique in the whole Kubernetes cluster. In our case, these are the IP addresses 10.0.12.3 and 10.0.12.5. Both are part of a private subnet managed by the Kubernetes network driver.

A pod can contain one to many containers...