Getting Started with Kubernetes - Second Edition

Jonathan Baier

• Éditeur: Packt Publishing
• Année: 2017
• ISBN:
  9781787284135
• Édition: 2
• Sujet: Ciencia de la computación
• Sous-sujet: Virtualización

Learn how to schedule and run application containers using Kubernetes.About This Book• Get well-versed with the fundamentals of Kubernetes and get it production-ready for deployments• Confidently manage your container clusters and networks using Kubernetes• This practical guide will show you container application examples throughout to illustrate the concepts and features of KubernetesWho This Book Is ForThis book is for developers, sys admins, and DevOps engineers who want to automate the deployment process and scale their applications. You do not need any knowledge about Kubernetes.What You Will Learn• Download, install, and configure the Kubernetes codebase• Understand the core concepts of a Kubernetes cluster• Be able to set up and access monitoring and logging for Kubernetes clusters• Set up external access to applications running in the cluster• Understand how CoreOS and Kubernetes can help you achieve greater performance and container implementation agility• Run multiple clusters and manage from a single control plane• Explore container security as well as securing Kubernetes clusters• Work with third-party extensions and toolsIn DetailKubernetes has continued to grow and achieve broad adoption across various industries, helping you to orchestrate and automate container deployments on a massive scale.This book will give you a complete understanding of Kubernetes and how to get a cluster up and running. You will develop an understanding of the installation and configuration process. The book will then focus on the core Kubernetes constructs such as pods, services, replica sets, replication controllers, and labels. You will also understand how cluster level networking is done in Kubernetes.The book will also show you how to manage deployments and perform updates with minimal downtime. Additionally, you will learn about operational aspects of Kubernetes such as monitoring and logging. Advanced concepts such as container security and cluster federation will also be covered. Finally, you will learn about the wider Kubernetes ecosystem with OCP, CoreOS, and Tectonic and explore the third-party extensions and tools that can be used with Kubernetes.By the end of the book, you will have a complete understanding of the Kubernetes platform and will start deploying applications on it.Style and approachThis straightforward guide will help you understand how to move your container applications into production through best practices and a step-by-step walkthrough tied to real-world operational strategies.

Introduction to Kubernetes

In this book, we will help you learn to build and manage Kubernetes clusters. You will be given some of the basic container concepts and the operational context, wherever possible. Throughout the book, you'll be given examples that you can apply as you progress through the book. By the end of the book, you should have a solid foundation and even dabble in some of the more advance topics such as federation and security.

This chapter will give a brief overview of containers and how they work as well as why management and orchestration is important to your business and/or project team. The chapter will also give a brief overview of how Kubernetes orchestration can enhance our container management strategy and how we can get a basic Kubernetes cluster up, running, and ready for container deployments.

This chapter will include the following topics:

• Introducing container operations and management
• Why container management is important?
• The advantages of Kubernetes
• Downloading the latest Kubernetes
• Installing and starting up a new Kubernetes cluster
• The components of a Kubernetes cluster

A brief overview of containers

Over the past three years, containers have grown in popularity like wildfire. You would be hard-pressed to attend an IT conference without finding popular sessions on Docker or containers in general.

Docker lies at the heart of the mass adoption and the excitement in the container space. As Malcom McLean revolutionized the physical shipping world in the 1950s by creating a standardized shipping container, which is used today for everything from ice cube trays to automobiles (you can refer to more details about this in point 1 in the References section at the end of the chapter), Linux containers are revolutionizing the software development world by making application environments portable and consistent across the infrastructure landscape. As an organization, Docker has taken the existing container technology to a new level by making it easy to implement and replicate across environments and providers.

What is a container?

At the core of container technology are control groups (cgroups) and namespaces. Additionally, Docker uses union filesystems for added benefits to the container development process.

Cgroups work by allowing the host to share and also limit the resources each process or container can consume. This is important for both, resource utilization and security, as it prevents denial-of-service attacks on the host's hardware resources. Several containers can share CPU and memory while staying within the predefined constraints.

Namespaces offer another form of isolation for process interaction within operating systems. Namespaces limit the visibility a process has on other processes, networking, filesystems, and user ID components. Container processes are limited to see only what is in the same namespace. Processes from containers or the host processes are not directly accessible from within this container process. Additionally, Docker gives each container its own networking stack that protects the sockets and interfaces in a similar fashion.

Composition of a container

Union filesystems are also a key advantage of using Docker containers. Containers run from an image. Much like an image in the VM or Cloud world, it represents state at a particular point in time. Container images snapshot the filesystem, but tend to be much smaller than a VM. The container shares the host kernel and generally runs a much smaller set of processes, so the filesystem and boot strap period tend to be much smaller. Though those constraints are not strictly enforced. Second, the union filesystem allows for efficient storage, download, and execution of these images.

The easiest way to understand union filesystems is to think of them like a layer cake with each layer baked independently. The Linux kernel is our base layer; then, we might add an OS such as Red Hat Linux or Ubuntu. Next, we might add an application such as Nginx or Apache. Every change creates a new layer. Finally, as you make changes and new layers are added, you'll always have a top layer (think frosting) that is a writable layer.

Layered filesystem

What makes this truly efficient is that Docker caches the layers the first time we build them. So, let's say that we have an image with Ubuntu and then add Apache and build the image. Next, we build MySQL with Ubuntu as the base. The second build will be much faster because the Ubuntu layer is already cached. Essentially, our chocolate and vanilla layers, from the preceding Layered filesystem figure, are already baked. We simply need to bake the pistachio (MySQL) layer, assemble, and add the icing (the writable layer).

Why are containers so cool?

Containers on their own are not a new technology and have in fact been around for many years. What truly sets Docker apart is the tooling and ease of use they have brought to the community. Modern development practices promote the use of Continuous Integration and Continuous Deployment. These techniques, when done right, can have a profound impact on your software product quality.

The advantages of Continuous Integration/Continuous Deployment

ThoughtWorks defines Continuous Integration as a development practice that requires developers to integrate code into a shared repository several times a day. By having a continuous process of building and deploying code, organizations are able to instill quality control and testing as part of the everyday work cycle. The result is that updates and bug fixes happen much faster and the overall quality improves.

However, there has always been a challenge in creating development environments that match that of testing and production. Often inconsistencies i...