Jump right into Kubernetes development with career-focused lessons and hands-on practice.

DevOps for Developers

Kubernetes is a powerful container management tool that's taking the world by storm. This detailed course will help you master it.

In this course, you'll start with the fundamentals of Kubernetes and what the main components of a cluster look like. You'll then learn how to use those components to build, test, deploy, and upgrade applications, as well as how to achieve state persistence once your application is deployed. You'll also learn how to secure your deployments and manage resources, which are crucial DevOps skills.

By the time you're done, you'll have a firm grasp on what Kubernetes is, as well as the skills to deploy your own clusters and applications with confidence.

A Practical Guide to Kubernetes

# Understanding ReplicaSets
> **Note:** Most applications should be scalable fault tolerant. While Pods do not provide those features, **ReplicaSets** do.

Previously, we learned that Pods are the smallest unit in Kubernetes. We also learned that Pods are _not_ fault tolerant. If a Pod is created without a controller and subsequently destroyed, Kubernetes does nothing to remedy the problem.

The first Controller we'll explore is called **ReplicaSet**. Its primary function is to ensure that a specified number of replicas of a Pod match the Pod's actual state (almost) all the time. This means that ReplicaSets make Pods scalable.

We can think of ReplicaSets as a *self-healing* mechanism. As long as elementary conditions are met (e.g., enough memory and CPU), Pods associated with a ReplicaSet are guaranteed to run. They provide fault tolerance and high availability.

 If you're familiar with Replication-Controllers, it is worth mentioning that the ReplicaSet is the next-generation *ReplicationController*. The only significant difference is that ReplicaSet has extended support for selectors. Everything else is the same. ReplicationController is considered deprecated, so we'll focus only on ReplicaSet.

> **Note:** ReplicaSet's primary function is to ensure that the specified number of replicas of service are (almost) always running.

Let's explore ReplicaSet in this chapter through examples to see how it works.





Learn about ReplicaSets and their significance in Kubernetes. 

Getting Started with ReplicaSets

Learn about ReplicaSets and their significance in Kubernetes.