Kubeadm with Calico Pod Network

  The kubeadm tool helps you bootstrap a minimum viable Kubernetes cluster that conforms to best practices.

The kubeadm tool is good if you need:

  • A simple way for you to try out Kubernetes, possibly for the first time.
  • A way for existing users to automate setting up a cluster and test their application.
  • A building block in other ecosystem and/or installer tools with a larger scope.

Before you begin

To follow this guide, you need:

  • One or more machines running a deb/rpm-compatible Linux OS; for example: Ubuntu or CentOS.
  • 2 GiB or more of RAM per machine--any less leaves little room for your apps.
  • At least 2 CPUs on the machine that you use as a control-plane node.
  • Full network connectivity among all machines in the cluster. You can use either a public or a private network.

Check required ports

Control-plane node(s)

Protocol

Direction

Port Range

Purpose

Used By

TCP

Inbound

6443*

Kubernetes API server

All

TCP

Inbound

2379-2380

etcd server client API

kube-apiserver, etcd

TCP

Inbound

10250

Kubelet API

Self, Control plane

TCP

Inbound

10251

kube-scheduler

Self

TCP

Inbound

10252

kube-controller-manager

Self

Worker node(s)

Protocol

Direction

Port Range

Purpose

Used By

TCP

Inbound

10250

Kubelet API

Self, Control plane

TCP

Inbound

30000-32767

NodePort Services†

All

 

Installing runtime

By default, Kubernetes uses the Container Runtime Interface (CRI) to interface with your chosen container runtime.

If you don't specify a runtime, kubeadm automatically tries to detect an installed container runtime by scanning through a list of well known Unix domain sockets.

Runtime

Path to Unix domain socket

Docker

/var/run/docker.sock

containerd

/run/containerd/containerd.sock

CRI-O

/var/run/crio/crio.sock


If both Docker and containerd are detected, Docker takes precedence. This is needed because Docker 18.09 ships with containerd and both are detectable even if you only installed Docker. If any other two or more runtimes are detected, kubeadm exits with an error.

Installing kubeadm, kubelet and kubectl

·       kubeadm: the command to bootstrap the cluster.

·       kubelet: the component that runs on all of the machines in your cluster and does things like starting pods and containers.

·       kubectl: the command line util to talk to your cluster.

Infrastructure

Lets Create 3 VirtualMachines(VMs) (1 Master Node and 2 Worker node). There must be network connectivity among these VMs

Installation on Ubuntu (Both on Master and Worker Nodes)

sudo apt-get update && sudo apt-get install -y apt-transport-https curl

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

cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list

deb https://apt.kubernetes.io/ kubernetes-xenial main

EOF

sudo apt-get update

sudo apt-get install -y kubelet kubeadm kubectl

sudo apt-mark hold kubelet kubeadm kubectl

 


Installation on RHEL/CentOS (Both on Master and Worker Nodes)

In case if you are using CentOS/RHEL

cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-\$basearch
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg \
   https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
exclude=kubelet kubeadm kubectl
EOF
 
# Set SELinux in permissive mode (effectively disabling it)
sudo setenforce 0
sudo sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config
sudo yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
sudo systemctl enable --now kubelet


Create Master Server

On master machine run the below command

1.  kubeadm init --apiserver-advertise-address=<<Master ServerIP>> --pod-network-cidr=192.168.0.0/16

2.  mkdir -p $HOME/.kube

3.  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

4.  sudo chown $(id -u):$(id -g) $HOME/.kube/config

yaml file is to be applied

5.  Run the join command on each of the worker node which you want to join in the cluser.

 kubectl apply -f <.yml>

7.  Run kubectl get nodes command on master node

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