Create a Cluster

Kubernetes cluster, Minikube

Using Minikube to Create a Cluster

  • Kubernetes cluster: a highly available cluster of computers that are connected to work as a single unit

  • you can deploy an application to a cluster without tying them to a specific machine

  • containerizing applications makes sure that they are packaged in a way that decouples them from individual hosts

    • containerized apps are more flexible and available than apps that are installed directly onto specific machines

  • Kubernetes automates the distribution and scheduling of application containers across a cluster in a more efficient way

  • a Kubernetes cluster consists of two types of resources:

    • the Master coordinates the cluster

    • Nodes are the workers that run applications

  • The master manages the cluster by coordinating all activities

    • schedules applications

    • maintaining applications' desired state

    • scales applications

    • rolls out new updates

  • A node is a virtual machine (VM) or a physical computer that serves as a worker machine in a Kubernetes cluster

    • each node has a Kubelet, an agent for managing the node and communicating with the Kubernetes master

    • the node should have tools for handling container operations

      • e.g. Docker or rkt

    • a Kubernetes cluster that handles production traffic should have a minimum of three nodes

Masters manage the cluster and the nodes that are used to host the running applications.

  • when deploying apps to Kubernetes, you tell the master to start the application containers

  • the master schedules the containers to run on the cluster's nodes

  • the nodes communicate with the master using the Kubernetes API, which the master exposes

  • end users can use the Kubernetes API directly to interact with the cluster

  • a Kubernetes cluster can be deployed on either physical or virtual machines

  • you can use Minikube to start with Kubernetes development

    • Minikube: a lightweight Kubernetes implementation that creates a VM on your local machine and deploys a simple cluster containing a single node

      • available for Linux, macOS, Windows

    • provides basic bootstrapping operations for working with your cluster

      • e.g. start, stop, status, delete

Interactive Tutorial: Creating a Cluster

Cluster up and running

minikube version - check that minikube is properly installed

$ minikube version
minikube version: v1.8.1
commit: cbda04cf6bbe65e987ae52bb393c10099ab62014

minikube start - start the cluster

$ minikube start
* minikube v1.8.1 on Ubuntu 18.04
* Using the none driver based on user configuration
* Running on localhost (CPUs=2, Memory=2460MB, Disk=145651MB) ...
* OS release is Ubuntu 18.04.4 LTS
* Preparing Kubernetes v1.17.3 on Docker 19.03.6 ...
  - kubelet.resolv-conf=/run/systemd/resolve/resolv.conf
* Launching Kubernetes ...
* Enabling addons: default-storageclass, storage-provisioner
* Configuring local host environment ...
* Waiting for cluster to come online ...
* Done! kubectl is now configured to use "minikube"

  • once you run those commands, you'll have a running Kubernetes cluster in your online terminal

  • Minikube started a VM that has a Kubernetes cluster running inside

Cluster version

  • you can use the kubectl command line interface to interact with Kubernetes

kubectl version - check if kubectl is installed

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"17", GitVersion:"v1.17.3", GitCommit:"06ad960bfd03b39c8310aaf92d1e7c12ce618213", GitTreeState:"clean", BuildDate:"2020-02-11T18:14:22Z", GoVersion:"go1.13.6", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"17", GitVersion:"v1.17.3", GitCommit:"06ad960bfd03b39c8310aaf92d1e7c12ce618213", GitTreeState:"clean", BuildDate:"2020-02-11T18:07:13Z", GoVersion:"go1.13.6", Compiler:"gc", Platform:"linux/amd64"}

  • you can see both the client version and the server version once you run kubectl version

    • client version: kubectl version

    • server version: Kubernetes version installed on the master

  • you can also see details about the build

Cluster details

kubectl cluster-info - view the cluster details

$ kubectl cluster-info
Kubernetes master is running at https://172.17.0.41:8443
KubeDNS is running at https://172.17.0.41:8443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

kubectl get nodes - view the nodes in the cluster

$ kubectl get nodes
NAME       STATUS   ROLES    AGE     VERSION
minikube   Ready    master   3m13s   v1.17.3

  • shows all nodes that can be used to host applications

  • we have one node that is ready (to accept applications for deployment)

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