This content originally appeared on DEV Community and was authored by Saravanan G
Kubernetes Learning Series - Part II
Table of contents
- Introduction
- Kubernetes High Level Architecture
- Control Plane
- Node
- Kubernetes Tools
- What is Minikube
- Minikube Installation Steps
- Install Curl
- Install docker
- Install Minikube
- Minikube Run
- Sample Output of minikube start and status
- Install Kubectl
- Verify and Run Minikube Cluster
- Conclusion
- Bibliography
Introduction
- In this article we will discuss the Kubernetes architecture and how to set up the lab environment to run the Kubernetes commands.
- This blog is part of the Kubernetes Learning series
- In the previous blog, we discussed about architecture decision that provides when to choose k8s for our application deployments
Kubernetes High Level Architecture
- Let us now discuss Kubernetes Architecture and components
- Kubernetes has two major building blocks,
- Kubernetes
Control Plane(orMaster Nodeas called previously) -
Nodes(orWorker Nodeas called previously)
- Kubernetes
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 getting started with Kubernetes by doing the setup in User Workstation
- Tools that provide local cluster,
- Minikube
- Kind
- Tools to interact with Kubernetes
- Kubectl
- Kubeadm
As part of learning and to practice Kubernetes, we will pick-up minikube installation steps.
Refer documentation for more details
What is Minikube
-
minikubeis a CLI tool that lets you run Kubernetes cluster 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,
Version information
While writing this article, Kubernetes version is 1.23.0 and minikube version is 1.25.2
Minikube Installation Steps
-
In order to getting started with
minikube, we need to install below components in our workstation- Install
curlcommand - Install
docker - Install
minikube - Install
kubectl
- Install
I have carried out the steps in
Ubuntu 21.04based operating systemRefer
minikubedocumentation 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
minikubecluster and provide docker as the container runtime engine
$ minikube start --driver=docker
- If we want to run
minikubewith specific version of kubernetes, it can done using the option--kubernetes-version,
minikube start --kubernetes-version=v1.11.10
Sample 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
-
minikubecomes with the desired version ofkubectlso, if we don't installkubectlexplicitly, then we can invokekubectlcommands as below,
minikube kubectl -- <expected kubectl command>
- Otherwise, follow the
kubectlinstallation doc to install it - If we installed
kubectl, then we can invokekubectlcommands as below,
kubectl <expected kubectl command>
Kubectl installation steps for Ubuntu,
Run below commands to install kubectl
sudo snap install kubectl --classic
kubectl version
Verify and Run Minikube Cluster
- We can use
kubectlcommands 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
- 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 covered kubernetes architecture understanding and gone through the setup of lab for k8s hands-on
- Try out and start hands-on with Kubernetes and let me know your feedback
- This article previously published on my dev community personal profile, re-publishing for the benefit of a wider audience.
- Hope this article is helpful to people getting started with kubernetes.
Thanks for reading!
Heads up for Next Blog
We will further explore topics like deployment of pods and services in next blog
Follow me and share your thoughts,
Bibliography
Kubernetes official documentation
Minikube documentation
This content originally appeared on DEV Community and was authored by Saravanan G
Saravanan G | Sciencx (2022-04-18T10:43:35+00:00) Kubernetes Learning Part II – Understanding of Kubernetes Architecture and Hands-on Lab Setup. Retrieved from https://www.scien.cx/2022/04/18/kubernetes-learning-part-ii-understanding-of-kubernetes-architecture-and-hands-on-lab-setup/
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