Install Kubernetes with Kubeadm

Installing Kubernetes can be tricky but this is made simpler with kubeadm tool. Whenever we install Kubernetes we need to take care of the parts involved in installation.

INSTALL KUBERNETES USING KUBEADM

Pre-Requisites (Official Documentation)

1. Compatible Linux host(s).
2. First identify how many Leader nodes and How many Follower nodes are to be deployed.
3. Ensure you are having root user access for these nodes.
4. Ensure you are having internet access from these nodes.
5. 2 GB or more of RAM per machine and 2 CPUs or more. Resources of leader will be more than that of follower (any less will leave little room for your apps).
6. Unique hostname, MAC address, and product_uuid for every node.
7. Certain ports are open on your machines.
8. Swap disabled. You MUST disable swap in order for the kubelet to work properly.

Ports Need to be available by default across cluster nodes.

Leader Nodes:

Follower Nodes:

Prepare the Nodes

• Set hostnames for the nodes.

hostnamectl set-hostname kube-leader (on leader server)
hostnamectl set-hostname kube-follower (on follower server)

• Get the IP Adress of all nodes by using ifconfig -a or hostname -i and run on all nodes.

echo "172.31.15.56 kube-leader" >> /etc/hosts
echo "172.31.26.16 kube-follower" >> /etc/hosts

• Check the ping utility.

ping kube-leader
ping kube-follower

• Turn off swap and disable firewall

swapoff -a
sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab
systemctl stop firewalld
systemctl disable firewalld

Install Container Runtime (containerd) [ CentOS / RHEL ]

This step needs to be followed on all nodes [Leader and Follower]

• Steps to install containerd in [CentOS/RHEL]

dnf install -y  yum-utils device-mapper-persistent-data lvm2

dnf config-manager --add-repo=https://download.docker.com/linux/centos/docker-ce.repo

dnf update -y && dnf install -y containerd.io

mkdir -p /etc/containerd

containerd config default > /etc/containerd/config.toml# Restart containerd

systemctl restart containerd

systemctl enable containerd

systemctl status containerd

• Download crictl executable for checking the successfull status of containerd | Official Documentation

VERSION="v1.26.0"
wget https://github.com/kubernetes-sigs/cri-tools/releases/download/$VERSION/crictl-$VERSION-linux-amd64.tar.gz
sudo tar zxvf crictl-$VERSION-linux-amd64.tar.gz -C /usr/local/bin
rm -f crictl-$VERSION-linux-amd64.tar.gz

• Add the below lines in the file: /etc/crictl.yaml

runtime-endpoint: unix:///var/run/containerd/containerd.sock
image-endpoint: unix:///var/run/containerd/containerd.sock
timeout: 2

• Run crictl images and crictl ps -a to ensure containerd is successfully runing.

Install Kubeadm ,Kubectl ,Kubelet

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
gpgkey=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

• Run the Below Command in Leader Node

sudo yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
sudo systemctl enable --now kubelet

• Run the Below Command in Follower Node

sudo yum install -y kubelet kubeadm --disableexcludes=kubernetes
sudo systemctl enable --now kubelet

Initialize cluster using kubeadm

• Get The Leader Node IP Address using the command ifconfig -a or hostname -i
• Use the IP Address in --apiserver-advertise-address flag
• The below command is used only in Leader Nodes

kubeadm init --apiserver-advertise-address=10.184.42.29 --pod-network-cidr=192.168.0.0/16  --service-cidr=192.168.0.0/17

• The above command will output a command like kubeadm join ...... Collect the same command and run it in Follower Nodes.

Install CNI (Container Network Interface) for the cluser

• We are going to install Calico as a CNI in the cluster Run the Below Command in Leader Node

kubectl apply -f https://docs.projectcalico.org/v3.8/manifests/calico.yaml

Verify the Kubernetes Cluster Installation

• Run the below command only in leader nodes.

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

• Verify the cluster is working fine by using the below command. kubectl get nodes kubectl get pods --all-namespaces