Configure Kubernetes cluster on Ubuntu 18.04.1

Depending on availability, you may download and install Ubuntu on either VMware workstation/fusion or get a playground servers on online lab platforms.

System requirements:

Kubernetes Master Node:
VCPU = 2
Memory 2 GB
label= k8-Master
Network Adapter: Bridge Networking
Static IP: <ip>/24
Kubernetes Client Node 1:
VCPU = 1
Memory = 1 GB
label= k8-Worker1
Network Adapter: Bridge Networking
Static IP: <ip>/24
Kubernetes Client Node 2:
VCPU = 1
Memory = 1 GB
label= k8-Worker2
Network Adapter: Bridge Networking
Static IP: <ip>/24

Step1:

Install below pre-requisites on all 3 servers for k8 to function as expected

sudo swapoff /swapfile
apt-get update && sudo apt-get install -y \
  apt-transport-https ca-certificates curl software-properties-common gnupg2
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key --keyring /etc/apt/trusted.gpg.d/docker.gpg add -
add-apt-repository \
  "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) \
  stable"
apt-get update && sudo apt-get install -y \
  containerd.io=1.2.13-2 \
  docker-ce=5:19.03.11~3-0~ubuntu-$(lsb_release -cs) \
  docker-ce-cli=5:19.03.11~3-0~ubuntu-$(lsb_release -cs)
cat <<EOF | sudo tee /etc/docker/daemon.json
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2"
}
EOF
mkdir -p /etc/systemd/system/docker.service.d
systemctl daemon-reload
systemctl restart docker
 
dpkg -l | grep docker
hi  docker-ce                            18.06.3~ce~3-0~ubuntu               amd64        Docker: the open-source application container engine
# sudo apt-mark hold docker-ce
apt-get update && sudo apt-get install -y apt-transport-https curl

verify docker version on all 3 nodes

# sudo docker version

Step 2: Install kubeadm, kubelet and kubectl on all 3 nodes

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

At this moment, kubectl and kubelet command wouldn’t work since we didn’t form k8 cluster

Step3: Bootstrap cluster -

On k8 master node, initialize the cluster and observer if there are any errors.

kubeadm init --pod-network-cidr=10.244.0.0/16
mkdir -p $HOME/.kube
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config
ls -lah $HOME/.kube/config
-rw------- 1 root root 5.4K Nov  2 12:26 /root/.kube/config

Verify and ensure kubectl is responsive on master node

Step 4: Join worker nodes to Master

During kubeadm init operation, you would have got the token and cert details. Join the worker nodes to master with cert and token

kubeadm join <masterip>:6443 --token <token> --discovery-token-ca-cert-hash <cert>

Now from master, verify that all nodes have successfully joined cluster. The nodes are expected to have status ‘NotReady’ at this point

Step 5: Configure Networking

We have setup kube cluster but haven’t configured cluster networking for cluster to be fully operational

On all nodes, update iptables

echo "net.bridge.bridge-nf-call-iptables=1" | sudo tee -a /etc/sysctl.conf

Calico is one of the widely used component for networking in k8. Install it on cluster with below cmds (only on master)

curl https://docs.projectcalico.org/manifests/calico.yaml -O
kubectl apply -f calico.yaml

Check node status with ‘kubectl get nodes’. Create a new pod and ensure status returned as ‘running’

kubectl get nodes
kubectl run nginx --image=nginx
$ kubectl get pods
NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          11s