Creating a Kubernetes Cluster

Install Docker and Kubernetes on All Servers

Nodes

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, reload systemd, then 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 Kubernetes repo:

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 v1.14.0:

yum install -y kubelet-1.14.0-0 kubeadm-1.14.0-0 kubectl-1.14.0-0 kubernetes-cni-0.7.5

Enable the kubelet service. The kubelet service will fail to start until the cluster is initialized, this is expected:

systemctl enable kubelet

Master

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, reload systemd, then 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 Kubernetes repo:

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 v1.14.0:

yum install -y kubelet-1.14.0-0 kubeadm-1.14.0-0 kubectl-1.14.0-0 kubernetes-cni-0.7.5

Enable the kubelet service. The kubelet service will fail to start until the cluster is initialized, this is expected:

systemctl enable kubelet

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.

Nodes

Login back to the node and run the kubeadm command from master

kubeadm join 10.0.1.100:6443 --token 8j9ng5.9dmce3s6rnhyx6ez \
    --discovery-token-ca-cert-hash sha256:48adc8e2ae7e83d92ec143f1720c4652da7c4703f0ca0197bf9d7a3bf6b5210b

Master

Exit sudo, copy the admin.conf to your home directory, and take ownership.

exit 
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/flannel-io/flannel/master/Documentation/kube-flannel-old.yaml

Check the cluster state:

kubectl get pods --all-namespaces
kubectl get nodes

Create and Scale a Deployment Using kubectl

Master

Create a simple deployment:

kubectl create deployment nginx --image=nginx

Inspect the pod:

kubectl get pods

Scale the deployment:

kubectl scale deployment nginx --replicas=4

Inspect the pods. We should have four now:

kubectl get pods