How to Install Kubernetes Cluster on Ubuntu 20.04 LTS
This tutorial will help you with step by step procedure for installing and configuring kubernetes multinode cluster with Docker on Ubuntu 20.04 LTS using Kubeadm and Kubectl.
Let’s get started.
How to Install Kubernetes Cluster on Ubuntu 20.04 LTS
Our Lab Setup:
Prerequisites:
1. Minimum 2 CPU’s with 4Gb Memory is required.
2. Make an entry of each host in /etc/hosts file for name resolution on all kubernetes nodes as below or configure it on DNS if you have DNS server.
Below are the steps to install the cluster once the VMs are provisioned.
I have created a detailed video on how to create VMs on google cloud and install the cluster using kubeadm, below is the link.
Ports and Protocols
When running Kubernetes in an environment with strict network boundaries, such as on-premises datacenter with physical network firewalls or Virtual Networks in Public Cloud, it is useful to be aware of the ports and protocols used by Kubernetes components
Control plane
| 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 | 10259 | kube-scheduler | Self |
| TCP | Inbound | 10257 | kube-controller-manager | Self |
Although etcd ports are included in control plane section, you can also host your own etcd cluster externally or on custom ports.
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 |
Set up the Docker and Kubernetes repositories:
Download the GPG key for docker in both master and worker node1 and node2
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
Add the docker repository in both master and worker node1 and node2
We can get the latest release versions from https://docs.docker.com
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
Add the GPG key for Kubernetes in both master and worker node1 and node2
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
Add the kubernetes repository in both master and worker node1 and node2
Check for the latest release in https://packages.cloud.google.com/apt/dists
cat << EOF | sudo tee /etc/apt/sources.list.d/kubernetes.listdeb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
Update the repository in both master and worker node1 and node2
# Update the repositries
sudo apt-get update
Install Docker and Kubernetes packages in both master and worker node1 and node2
Note that if you want to use a newer version of Kubernetes, change the version installed for kubelet, kubeadm, and kubectl and be sure that all three use the same version. These version should support the Docker CE version.
# Use the same versions to avoid issues with the installation.
sudo apt-get install -y docker-ce=5:19.03.13~3-0~ubuntu-$(lsb_release -cs) kubelet=1.19.4-00 kubeadm=1.19.4-00 kubectl=1.19.4-00
To hold the versions so that the versions will not get accidently upgraded in both master and worker node1 and node2
sudo apt-mark hold docker-ce kubelet kubeadm kubectl
Enable the iptables bridge in both master and worker node1 and node2
#Set a value in the sysctl file , to allow proper network settings for Kubernetes on all the servers.
echo "net.bridge.bridge-nf-call-iptables=1" | sudo tee -a /etc/sysctl.conf
#To make the changes to take immediate effect for the iptables
sudo sysctl -p
On the Kubernetes master server
Initialize the cluster by passing the cidr value and the value will depend on the type of network CLI you choose.
Use either Flannel or Calico ( we are using Calico in this lab)
# For flannel network
sudo kubeadm init --pod-network-cidr=10.244.0.0/16
# Copy your join command and keep it safe.
# Below is a sample
sudo kubeadm join 10.128.0.2:6443 --token swi0ci.jq9l75eg8lvpxz6g --discovery-token-ca-cert-hash sha256:2c3cdfa898334b0dfc0f73bbccb998d03f61252ee50f0405c85ba735ff90b4d1
# For Calico network
sudo kubeadm init --pod-network-cidr=192.168.0.0/16
# Copy your join command and keep it safe.
sudo kubeadm join 10.128.0.2:6443 --token swi0ci.jq9l75eg8lvpxz6g --discovery-token-ca-cert-hash sha256:2c3cdfa898334b0dfc0f73bbccb998d03f61252ee50f0405c85ba735ff90b4d1
To start using the cluster with current user . ( Do this command on master only)
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
To set the flannel networking ( Do this on master only)
# Use this if you have initialized the cluster with Flannel network add on.
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
To set up the Calico network ( Do this on master only)
# Use this if you have initialized the cluster with Calico network add on.
kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml
Check the nodes
# Check the status on the master node.
kubectl get nodes
On each of Kube node server
Joining the node to the cluster:
sudo kubeadm join $controller_private_ip:6443 --token $token --discovery-token-ca-cert-hash $hash
TIP
If the joining code is lost, it can retrieve using below command
kubeadm token create --print-join-command
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