kubernetes

Kubernetes

Introduction

• Kubernetes is an open source platform for managing container technologies such as Docker.

• Docker lets you create containers for a pre-configured image and application.

• Kubernetes provides the next step, allowing you to balance loads between containers and run multiple containers across multiple systems.

NOTE: This guide will walk you through how to install Kubernetes on Ubuntu 18.04.

Prerequisites

• 2 or more Linux servers running Ubuntu 18.04
• Access to a user account on each system with sudo or root privileges
• The apt package manager, included by default
• Command-line/terminal window (Ctrl-Alt-T)

Steps to Install Kubernetes on Ubuntu

Set up Docker

Step 1: Install Docker

Kubernetes requires an existing Docker installation. If you already have Docker installed, skip ahead to Step 2.

If you do not have Kubernetes, install it by following these steps:

1. Update the package list with the command:

sudo apt-get update

2. Next, install Docker with the command:

sudo apt-get install docker.io

3. Repeat the process on each server that will act as a node.

4. Check the installation (and version) by entering the following:

docker ––version

Step 2: Start and Enable Docker

1. Set Docker to launch at boot by entering the following:

sudo systemctl enable docker

2. Verify Docker is running:

sudo systemctl status docker

NOTE: To start Docker if it’s not running:

sudo systemctl start docker

3. Repeat on all the other nodes.

Install Kubernetes

Step 3: Add Kubernetes Signing Key

Since you are downloading Kubernetes from a non-standard repository, it is essential to ensure that the software is authentic. This is done by adding a signing key.

1. Enter the following to add a signing key:

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add

NOTE: If you get an error that curl is not installed, install it with:

sudo apt-get install curl

2. Then repeat the previous command to install the signing keys. Repeat for each server node.

Step 4: Add Software Repositories

Kubernetes is not included in the default repositories. To add them, enter the following:

sudo apt-add-repository "deb http://apt.kubernetes.io/ kubernetes-xenial main"

Repeat on each server node.

Step 5: Kubernetes Installation Tools

Kubeadm (Kubernetes Admin) is a tool that helps initialize a cluster. It fast-tracks setup by using community-sourced best practices. Kubelet is the work package, which runs on every node and starts containers. The tool gives you command-line access to clusters.

1. Install Kubernetes tools with the command:

sudo apt-get install kubeadm kubelet kubectl
sudo apt-mark hold kubeadm kubelet kubectl

Allow the process to complete.

2. Verify the installation with:

kubeadm version

3. Repeat for each server node.

Kubernetes Deployment

Step 6: Begin Kubernetes Deployment Start by disabling the swap memory on each server:

sudo swapoff --a

Step 7: Assign Unique Hostname for Each Server Node

Decide which server to set as the master node. Then enter the command:

sudo hostnamectl set-hostname master-node

Next, set a worker node hostname by entering the following on the worker server:

sudo hostnamectl set-hostname worker01

If you have additional worker nodes, use this process to set a unique hostname on each.

Step 8: Initialize Kubernetes on Master Node Switch to the master server node, and enter the following:

sudo kubeadm init --pod-network-cidr=FILL_MASTER_IP_ADDRESS/16

sudo kubeadm init --pod-network-cidr=10.217.70.62/16

Note: Output

Once this command finishes, it will display a kubeadm join message at the end. Make a note of the whole entry. This will be used to join the worker nodes to the cluster.

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 10.217.70.62:6443 --token 4j9b95.1cdx9tadejremcm9 \
    --discovery-token-ca-cert-hash sha256:6c136ea5116ea3cdcbcdc9e7fa0eb941f16ed85ca5e67c73b2d3f9b1e56fc2ea 

Next, enter the following to create a directory for the cluster:

kubernetes-master:~$ mkdir -p $HOME/.kube
kubernetes-master:~$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
kubernetes-master:~$ sudo chown $(id -u):$(id -g) $HOME/.kube/config

Step 9: Deploy Pod Network to Cluster

A Pod Network is a way to allow communication between different nodes in the cluster. This tutorial uses the flannel virtual network.

Enter the following:

sudo kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Allow the process to complete. Verify that everything is running and communicating:

kubectl get pods --all-namespaces

Step 10: Join Worker Node to Cluster

As indicated in Step 7, you can enter the kubeadm join command on each worker node to connect it to the cluster. Switch to the worker01 system and enter the command you noted from Step 7:

kubeadm join 10.217.70.62:6443 --token 4j9b95.1cdx9tadejremcm9 \
    --discovery-token-ca-cert-hash sha256:6c136ea5116ea3cdcbcdc9e7fa0eb941f16ed85ca5e67c73b2d3f9b1e56fc2ea 

Replace the alphanumeric codes with those from your master server. Repeat for each worker node on the cluster. Wait a few minutes; then you can check the status of the nodes.

Switch to the master server, and enter:

kubectl get nodes

The system should display the worker nodes that you joined to the cluster.

Kubernetes Dashboard

Step 11: The Dashboard UI is not deployed by default. To deploy it, run the following command:

kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.0.3/aio/deploy/recommended.yaml

Step 12: To create a sample user account follow the instructions here

Step 13: You can access Dashboard using the kubectl command-line tool by running the following command:

kubectl proxy

Step 14: Kubectl will make Dashboard available at

http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/

Note: The UI can only be accessed from the machine where the command is executed. See kubectl proxy --help for more options.

Important

NOTE: If you have are having problems with master and worker nodes reset the Kubernetes using the following commands

sudo kubeadm reset