Getting Started Tutorial for Learning Kubernetes

Table of contents

• Introduction
• What is Kubernetes
• Kubernetes High Level Architecture
• Control Plane
• Node
• Kubernetes Tools
• What is Minikube
• Minikube Installation
• Install Curl
• Install docker
• Install Minikube
• Minikube Run
• Output of minikube start and status
• Install Kubectl
• Verify and Run Minikube Cluster
• Conclusion
• Bibliography

Introduction

• This article intended for the purpose of getting started with Kubernetes basics
• It also explains about setting up the labs environment to run the basic Kubernetes commands.
• You can consider this blog as scribble pad that is used while getting started with Kubernetes

What is Kubernetes

• Kubernetes (also called a K8s) is a Container orchestration open-source platform.
• Kubernetes builds upon 15 years of experience of running production workloads at Google, combined with best-of-breed ideas and practices from the community.
• We can manage containerised workloads and services, that facilitates both declarative configuration and automation.
• It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.
• Refer Documentation for more details

Kubernetes High Level Architecture

Kubernetes to two major building blocks,
1. Kubernetes Control Plane (or Master Node as called previously)
2. Nodes (or Worker Node as called previously)

Control Plane

Kubernetes Control Plane has four major components,
1. Kube API Server : This component exposes Kubernetes API and acts as a front end of k8s control plane. kubectl is used to interact with API servers.
2. ETCD : Secure key-value store
3. Kube Scheduler : Watches newly created Pod with and selects node for those pods to run
4. Controller Manager : This component manages the four controller processes of Kubernetes

• Node Controller
• Job Controller
• End-point Controller
• Service account & Token Controller

Node

A node consists of,
1. Kubelet : An agent that runs on each node in the cluster. It makes sure that containers are running in a Pod.
2. Kube-proxy : kube-proxy is a network proxy that runs on each node in your cluster, implementing part of the Kubernetes Service concept.
3. Container Runtime : The container runtime is the software that is responsible for running containers.
Kubernetes supports several container runtimes: Docker, containerd, CRI-O, and any implementation of the Kubernetes CRI (Container Runtime Interface).
4. Pods : Pods are the smallest deploy-able units of computing that we can create and manage in Kubernetes.
A Pod (as in a pod of whales or pea pod) is a group of one or more containers, with shared storage and network resources, and a specification for how to run the containers.

Refer Kubernetes Component Documentation for more details.

Kubernetes Tools

There are various tools available to learn Kubernetes by doing the setup in Workstation

• Minikube
• Kind
• Kubectl
• Kubeadm

As part of learning and to practice Kubernetes, we will pick-up minikube installation steps and practice lessons.

Refer documentation for more details

What is Minikube

• minikube is a CLI tool that lets you run Kubernetes locally on any workstation.
• It runs a single-node Kubernetes cluster on our personal computer (including Windows, macOS and Linux OS) so we can try out Kubernetes learning, and for any daily development work.
• Minikube cluster packs both the master and worker components for us to get started with managing the container.
• Below diagram depicts the minikube single node cluster,

Minikube Installation

• In order to getting started with minikube, we need to install below components in our workstation

  • Install curl command
  • Install docker
  • Install minikube
  • Install kubectl (optional)

• I have carried out the steps in Ubuntu 21.04 based operating system

• Refer minikube documentation for installation steps for other operating systems

Install curl

sudo apt update
sudo apt install curl -y

Install docker

# Update the apt package index, and install the latest version of Docker Engine and containerd, 
# or go to the next step to install a specific version:
sudo apt update -y
sudo apt install -y docker-ce docker-ce-cli containerd.io

# Add current user to 'docker' user group to invoke minikube (otherwise, the .sock permission denied error will occur)
sudo usermod -aG docker $USER
newgrp docker

# Verify that Docker Engine is installed correctly by running the hello-world image.
sudo docker run hello-world

Install Minikube

cd /tmp
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube_latest_amd64.deb
sudo dpkg -i minikube_latest_amd64.deb

Minikube Run

• Start minikube cluster and provide docker as the container runtime engine

$ minikube start --driver=docker

Output of minikube start and status

• It will show up the below output in console

😄  minikube v1.22.0 on Ubuntu 21.04
✨  Using the docker driver based on user configuration
👍  Starting control plane node minikube in cluster minikube
🚜  Pulling base image ...
💾  Downloading Kubernetes v1.21.2 preload ...
    > preloaded-images-k8s-v11-v1...: 502.14 MiB / 502.14 MiB  100.00% 7.75 MiB
    > gcr.io/k8s-minikube/kicbase...: 361.09 MiB / 361.09 MiB  100.00% 5.08 MiB
🔥  Creating docker container (CPUs=2, Memory=3900MB) ...
🐳  Preparing Kubernetes v1.21.2 on Docker 20.10.7 ...
    ▪ Generating certificates and keys ...
    ▪ Booting up control plane ...
    ▪ Configuring RBAC rules ...
🔎  Verifying Kubernetes components...
    ▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5
🌟  Enabled addons: storage-provisioner, default-storageclass
💡  kubectl not found. If you need it, try: 'minikube kubectl -- get pods -A'
🏄  Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default

• Minikube status command,

$ minikube status
minikube
type: Control Plane
host: Running
kubelet: Running
apiserver: Running
kubeconfig: Configured

Install Kubectl

Please note, Installation of Kubectl is options, because minikube comes packed desired version of kubectl
so, if we don't install kubectl explicitly, then we can invoke kubectl commands as below,

minikube kubectl -- <expected kubectl command>

If we explicitly installed kubectl, then we can invoke kubectl commands directly as below,

kubectl <expected kubectl command>

Kubectl installation steps,
Run below commands to install kubectl in ubuntu

sudo snap install kubectl --classic
kubectl version

Verify and Run Minikube Cluster

• We can use kubectl commands to verify the installed cluster and other details.
• We can use it to access our new cluster created using minikube

kubectl get po -A

or

minikube kubectl -- get po -A

• It shows the below output, which shows the deployed single node cluster created using minikube
• Please note components from control plane and worker node available as part of minikube deployment

$ kubectl get po -A
NAMESPACE              NAME                                         READY   STATUS    RESTARTS   AGE
kube-system            coredns-558bd4d5db-4tncm                     1/1     Running   5          9d
kube-system            etcd-minikube                                1/1     Running   5          9d
kube-system            kube-apiserver-minikube                      1/1     Running   5          9d
kube-system            kube-controller-manager-minikube             1/1     Running   5          9d
kube-system            kube-proxy-wtzn9                             1/1     Running   5          9d
kube-system            kube-scheduler-minikube                      1/1     Running   5          9d
kube-system            storage-provisioner                          1/1     Running   10         9d
kubernetes-dashboard   dashboard-metrics-scraper-7976b667d4-cssj8   1/1     Running   5          9d
kubernetes-dashboard   kubernetes-dashboard-6fcdf4f6d-kqr78         1/1     Running   10         9d

• Then, we can try performing the creation of new k8s deployments,

minikube kubectl -- create deployment hello-minikube --image=k8s.gcr.io/echoserver:1.4
minikube kubectl -- expose deployment hello-minikube --type=NodePort --port=8080

minikube kubectl -- get services hello-minikube
minikube service hello-minikube

• The entire Minikube cluster can be visualised using the below command,

minikube dashboard

Conclusion

• We have come to the end of kubernetes getting started tutorial - part 1
• Try this out and start hands-on with Kubernetes
• We will see, next level topics like deployment of pods and services in part 2

Bibliography

Kubernetes official documentation
Minikube documentation