install Kubernetes cluster

notes.txt

The first thing that we are going to do is use SSH to log in to all machines. Once we have logged in, we need to elevate privileges using sudo.
sudo su  
Disable SELinux.
setenforce 0
sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux
Enable the br_netfilter module for cluster communication.

modprobe br_netfilter
echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables
Ensure that the Docker dependencies are satisfied.

yum install -y yum-utils device-mapper-persistent-data lvm2
Add the Docker repo and install Docker.
yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
yum install -y docker-ce
Set the cgroup driver for Docker to systemd, then reload systemd, enable and start Docker
sed -i '/^ExecStart/ s/$/ --exec-opt native.cgroupdriver=systemd/' /usr/lib/systemd/system/docker.service
systemctl daemon-reload
systemctl enable docker --now
Add the repo for Kubernetes.
cat << EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg
https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF
Install Kubernetes.
yum install -y kubelet kubeadm kubectl
Enable the kubelet service. The kubelet service will fail to start until the cluster is initialized, this is expected.
systemctl enable kubelet
*Note: Complete the following section on the MASTER ONLY!
Initialize the cluster using the IP range for Flannel.
kubeadm init --pod-network-cidr=10.244.0.0/16
Copy the kubeadmn join command that is in the output. We will need this later.
Exit sudo and copy the admin.conf to your home directory and take ownership.
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Deploy Flannel.
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
Check the cluster state.

kubectl get pods --all-namespaces
Note: Complete the following steps on the NODES ONLY!

Run the join command that you copied earlier, this requires running the command as sudo on the nodes. Then check your nodes from the master.

kubectl get nodes