Introduction to Kubernetes

This repository contains the source code for creating a local Kubernetes cluster setup using either K3d or Rancher Kubernetes Engine (RKE). It also contains a set of manifest files to deploy a basic application to your local K8s cluster.

Slide Deck

The slide deck for the Introduction to Kubernetes course can be found in the slide-deck folder.

Install Rancher Desktop

Rancher Desktop, download the latest version of _Rancher Desktop_for your desktop operating system.

Install kubectl

This link for kubectl will cover the full installation of kubectl. Download and install kubectl for your desktop operating system.

Create Local Kubernetes Cluster with K3d

k3d is a lightweight wrapper to run k3s (Rancher Lab’s minimal Kubernetes distribution) in docker.

K3d Requirements/Prerequisites

• Docker
• Install K3d

Provision Cluster with K3d

The first step is to ensure that the docker engine is running on your machine. Once you've verified that, you can proceed to create a cluster with the following command:

k3d cluster create example-cluster --servers 3 --agents 2

Delete Cluster with K3d

You can delete a cluster with the following command:

k3d cluster delete example-cluster

Create Local Kubernetes Cluster with RKE

RKE is a CNCF-certified Kubernetes distribution that runs entirely within Docker containers.

RKE Requirements/Prerequisites

• Rancher Kubernetes Engine (RKE)
• Virtual Box
• Vagrant

Create Virtual Machines (VMs)

To spin up the virtual machines, run the following command at the root level of the project directory:

vagrant up

Once the VMs are up and running, you can check their status with vagrant status or by connecting to anyone of them using vagrant ssh [hostname]. Once you've confirmed that all machines are running with no issues, copy over the generated SSH keys from your workstation/host to each guest machine with the following commands:

ssh-copy-id root@[relevant ip address]

When prompted, enter the root user password configured in the bootstrap node script.

Provision/Create Kubernetes Cluster with RKE

To provision the cluster on the VMs, run the rke config command. You will be presented with a series of questions to which the answers will be used to declare the cluster config in a generated cluster.yml file upon completion. Alternatively, you can create the cluster.yml file and populate it with your desired configuration. Once you have the cluster.yml file, run the following command:

rke up

When the cluster has been provisioned, the following files will be generated in the root directory:

• cluster.rkestate - the cluster state file
• kube_config_cluster.yml - kube config file

To add the cluster to your context, copy the kube config file:

cp kube_config_cluster.yml ~/.kube/config

If you do not have a ./kube directory on your machine you will have to create one.

The last step will be to check that you can connect to your cluster:

kubectl cluster-info

or

kubectl config current-context

kubectl Exercises

No matter what cluster you are using k3s, k3d, RKE or even Rancher Desktop, you should be able to leverage the manifests located in the manifests folder. These are good to test out the kubectl and one of the aforementioned Kubernetes clusters.

Check your kubectl context

This command will let you know what of the many clusters your kubectl is pointed to:

kubectl config view

You should see something similar to this in the response:

current-context: rancher-desktop

Create a Pod

In your terminal change directories to the manifests folder in this GitHub repository.

Once you are in this directory you can run the following command to create a pod:

kubectl apply -f pod.yaml 

And you should see something like this as a response:

pod/express-test created

Describe a Pod

The describe command will give you the details on a particular object in the cluster. We are going to describe the pod that we just created:

kubectl describe pod express-test

The responses should look like something below (might not be exact):

Name:         express-test
Namespace:    default
Priority:     0
Node:         lima-rancher-desktop/192.168.5.15
Start Time:   Mon, 25 Oct 2021 08:40:45 -0400
Labels:       app=express-test
Annotations:  <none>
Status:       Running
IP:           10.42.0.36
IPs:
  IP:  10.42.0.36
Containers:
  express-test:
    Container ID:   containerd://f6d08505d3509140d575ff0e76762f622d26e8c3cc1d54b20713eb49ba91b3e2
    Image:          lukondefmwila/express-test:latest
    Image ID:       docker.io/lukondefmwila/express-test@sha256:c53f609cb6daadc3e161745c969b7446694205925fe2ce33f461b5c980cbd8ef
    Port:           8080/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Mon, 25 Oct 2021 08:40:54 -0400
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-2kwb2 (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-2kwb2:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-2kwb2
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                 node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age    From               Message
  ----    ------     ----   ----               -------
  Normal  Scheduled  8m12s  default-scheduler  Successfully assigned default/express-test to lima-rancher-desktop
  Normal  Pulling    8m12s  kubelet            Pulling image "lukondefmwila/express-test:latest"
  Normal  Pulled     8m3s   kubelet            Successfully pulled image "lukondefmwila/express-test:latest" in 8.463684s
  Normal  Created    8m3s   kubelet            Created container express-test
  Normal  Started    8m3s   kubelet            Started container express-test

Delete a Pod

The delete command can delete an object from your cluster. In this we will delete the pod we just created:

kubectl delete pod express-test

The output should look something like this:

pod "express-test" deleted