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

# Exploring the AWS ELB

We need a way to access the cluster. So far, we have seen that we can interact with the Kubernetes API. Every time we executed `kubectl`, it communicated with the cluster through the API server. That communication is established through AWS Elastic Load Balancer (ELB). Let’s take a quick look at it.

The output (limited to the relevant parts) is as follows:

{
  "LoadBalancerDescriptions": [
    {
      ...
      "ListenerDescriptions": [
        {
          "Listener": {
            "InstancePort": 443, 
            "LoadBalancerPort": 443, 
            "Protocol": "TCP", 
            "InstanceProtocol": "TCP"
          }, 
          ...
      "Instances": [
        {
          "InstanceId": "i-01f5c2ca47168b248"
        }, 
        {
          "InstanceId": "i-0305e3b2d3da6e1ce"
        }, 
        {
          "InstanceId": "i-04291ef2432b462f2"
        }
      ], 
      "DNSName": "api-devops23-k8s-local-ivnbim-1190013982.us-east-2.elb.amazonaws.com", 
      ...
      "LoadBalancerName": "api-devops23-k8s-local-ivnbim", 
      ...

Judging from the `Listener` section, we can see that only port `443` is opened,  allowing only SSL requests. 

The three instances belong to managers. We can safely assume that this load balancer is used only for access to Kubernetes API. In other words, we are still missing access to worker nodes through which we’ll be able to communicate with our applications. We’ll come back to this issue in a moment.

The entry that matters, from a user’s perspective, is `DNSName`. This is the address we need to use if we want to communicate with the Kubernetes API server. The load balancer is there to ensure that we have a fixed address and that requests will be forwarded to one of the healthy masters.

Finally, the name of the load balancer is `api-devops23-k8s-local-ivnbim`. It is important that you remember that it starts with `api-devops23`. You'll see soon why the name matters.

## Looking into the `kubectl` configuration
We can confirm that the `DNSName` is indeed the door to the API by examining `kubectl` configuration.

Learn how the different components in our cluster communicate with each other.

Accessing the Cluster: Understanding the Protocol

Exploring the AWS ELB