Book Image

The Kubernetes Book

By : Nigel Poulton, Pushkar Joglekar
Book Image

The Kubernetes Book

By: Nigel Poulton, Pushkar Joglekar

Overview of this book

Kubernetes is the leading orchestrator of cloud-native apps. With knowledge of how to work with Kubernetes, you can easily deploy and manage applications on the cloud or in your on-premises data center. The book begins by introducing you to Kubernetes and showing you how to install it. You’ll learn how to use Kubernetes Services and bring stable and reliable networking to apps that are deployed on Kubernetes. You'll delve deep into the powerful storage subsystem of Kubernetes and learn how to leverage the variety of external storage backends in your applications. As the book progresses, it shows you how to use features such as DaemonSets, Helm, and RBAC to enhance your Kubernetes applications. You'll explore the six categories of identifying vulnerabilities and look at a few ways to prevent and mitigate them. You'll also look at ways to secure the software delivery pipeline by discussing some image-related best practices. The book ends by sharing with you some resources that’ll help take your Kubernetes knowledge to the next level. By the end of the book, you’ll have the confidence and skills to leverage all the features of Kubernetes to develop scalable applications.
Table of Contents (23 chapters)
Free Chapter
1
Chapter 1
3
Chapter 2
5
Chapter 3
7
Chapter 4
9
Chapter 5
11
Chapter 6
13
Chapter 7
15
Chapter 8
17
Chapter 9
19
Chapter 10
21
Chapter 11

DaemonSets

DaemonSets manage Pods and are a resource in the apps API group. They're useful when you need a replica of a particular Pod running on every node in the cluster. Some examples include monitoring Pods and logging Pods that you need to run on every node in the cluster.

As you'd expect, it implements a controller and a watch loop. This means that you can dynamically add and remove nodes from the cluster, and the DaemonSet will ensure you always have one Pod replica on each of them.

The following command shows two DaemonSets in the kube-system namespace that exist on a newly installed three-node cluster.

The output is trimmed so that it fits the page:

kubectl get ds -n kube-system
NAME         DESIRED  CURRENT  READY  NODE SELECTOR
kube-proxy   3        3        3      beta.kubernetes.io/arch=amd64
weave-net    3        3        3      <none>

Notice that the desired state for each DaemonSet is three replicas. You do not need to specify this in...