Kubernetes K8s Setup on CentOS:7 with easy steps.

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Taking inspiration from and dedicated to our training guru, Shri Maninder sir.

Hey everyone! In this article, we'll learn how to set up a Kubernetes (k8s) cluster on a Linux CentOS 7 machine. You can do this either on cloud servers or virtual machines within your infrastructure.

If you are trying to set up a Kubernetes (k8s) cluster on an Ubuntu machine, try this article link: https://rakeshkumarjangid.hashnode.dev/how-to-setup-kubernetes-cluster-over-cloud-on-ubuntu-os, So let's start...

k8s Setting up on-premise virtual machines OR Cloud AWS Ec2 Instances.

Cluster Type	Specifications	OS Type
On-Primise VM (1 Master + 2 Worker)	4 GRB RAM, 2 Core, 20 GB storage in each machine	Centos:7
Cloud AWS	T2.Medium or up	AWS Linux

Step 1: Check your IP or create a network using `#nmcli`

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Note: This Step-1 is only for On-Primise VMs, not for cloud AWS instances. and execute this step-1 on all cluster nodes including the master node .

# cat /etc/os-release
# nmcli con show
NAME    UUID                                  TYPE      DEVICE
ens160  4443b0e3-1b19-3b0e-9861-7f0fbf825f6c  ethernet  ens160

*VMs Nodes-Private-IP*	VMs Node-Hostname
192.168.1.1	master.localhost.com
192.168.1.2	w1.localhost.com
192.168.1.3	w2.localhost.com

# hostnamectl set-hostname master.localhost.com && exec bash
# nmcli con mod ens160 ipv4.addresses 192.168.1.1/24 ipv4.gateway 192.168.1.255 ipv4.dns 8.8.8.8
# nmcli con up ens160

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Note: In the shortcut edit /etc/sysconfig/network-scripts/ifcfg-ensp* file.

# vi /etc/sysconfig/network-scripts/ifcfg-ensp***

IPADDR= ?   
NETMASK= ? 
GATEWAY=? 
DNS1=?

Mention the hostname and IP address in the /etc/hosts file

# vi /etc/hosts

192.168.1.1     www.master.localhost.com
192.168.1.2     www.w1.localhost.com
192.168.1.3     www.w2.localhost.com

:wq!

Step 2: Disable swap memory, selinux & firewall

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

# setenforce 0
# sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config

# systemctl disable firewalld && systemctl stop firewalld

# free -h
# sestatus
# systemctl statuts firewalld

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NOTE: Only From the master node, we'll generate a public key and then share it with the other worker nodes.

# ssh-keygen -t rsa
# ssh-copy-id -i /root/.ssh/id_rsa.pub root@192.168.1.X

Step 4: Install Docker-CE Engine (Execute on all master + slave nodes both)

# yum-config-manager --add-repo https://download.docker.com/linux/centos/dockerce.repo
# yum install -y yum-utils device-mapper-persistent-data lvm2
# yum install docker-ce-20* -y
# systemctl start docker && systemctl enable docker

Step 5: To update or add kernel arguments for both infra environments, and enable the bridge for all nodes including master.

# cat <<EOF > /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF

# sysctl --system

Step 6: Add Kubernetes Yum Repo from Google

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Note: Execute on all cluster nodes including the master node

# 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

Step 7: Install kubeadm, kubelet, kubectl packages

# yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes

Step 8: Start kubelet services agent

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Note: Execute on all cluster nodes including master node

# systemctl restart kubelet ; systemctl enable kubelet ; systemctl status kubelet

Step 9: Start Docker Host, containerd services (On all nodes including master)

# systemctl enable docker && systemctl restart docker

Step 10: Initialize kubeadm init command `(On Master Node only)`

# kubeadm init

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We will join the Worker node with the Master Node inside the Cluster in the future, so keep the output safe.

# echo "kubeadm join 172.31.4.165:6443 --token kw9d4k.l44fcziztb3br21a \
 --discovery-token-ca-cert-hash
sha256:2952821ac60c0ddb079cc82bd621a72e61aae08a4e700c4f8d457058d7f51dd7" > ~/join.txt

Step 11: Start cluster configuration at `MASTER NODE Only` with regular user.

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

Step 12: Download CNI Weave net `(Execute only on Master Node)` → ( Treated as Router)

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Official weave net link: <Official web page link>

$ https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml

Step 13: Go to the output of Step 10 and find the <`kubeadm join>` code and copy it at each worker node.

# kubeadm join 172.31.4.165:6443 --token kw9d4k.l44fcziztb3br21a \
 --discovery-token-ca-cert-hash
sha256:2952821ac60c0ddb079cc82bd621a72e61aae08a4e700c4f8d457058d7f51dd7

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Tip: If we forget join/hash code then we can run the following command :

# kubeadm token create --print-join-command

Step-14: Check the connected cluster status at the Master Node

$ kubectl get nodes -o wide

NAME                 STATUS    ROLES     AGE       VERSION   INTERNAL-IP     EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION      CONTAINER-RUNTIME
master.localhost.com   Ready     master    1d        1.27.2    192.168.1.1    <none>       CentOS Linux 7 (Core)   4.19.0-19-amd64     docker://20.10.7
w1.localhost.com       Ready     <none>    1d        1.27.2    192.168.1.2    <none>       CentOS Linux 7 (Core)   4.19.0-19-amd64     docker://20.10.7
w2.localhost.com       Ready     <none>    1d        1.27.2    192.168.1.3    <none>       CentOS Linux 7 (Core)   4.19.0-19-amd64     docker://20.10.7

$ kubectl get ns
$ kubectl get pods -n kube-system -o wide
$ kubect api-resources
$ kubectl get po -n kube-system -o wide

Congratulations to all. Thanks you sir

Kubernetes K8s Setup on CentOS:7 with easy steps.

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