Kubernetes Installation in RedHat/CentOS

Welcome! In this article, we are going to look at how to configure Kubernetes cluster for container orchestration.

Before reading this article, you should know basic core concepts of kubernetes components and basic administration in Redhat OS or CentOS

Prerequisites:

• Hosts - 2 or 3 Machines (node) requiredRAM - 4 GB
• Storage - 50 GB
• CPU - 2 CPU

Let’s start how to install and configure Kubernetes in Redhat Enterprise Linux.

Here we are going to configure Kubernetes cluster using 4 VM’s.

• One VM – Master Node
• Other three VM’s – Worker Nodes

Steps for Kubernetes Cluster Configuration

Step1: Set Hostname with its IP address

Add the Hostname of all Hosts with those IP address (Consider all Hosts or VM as Nodes)

Run the below command to go Hosts file location to change host name with its IP

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nano /etc/hosts

“Hostname with its IP (We need separate IP for each host or node)” 

We just gave the below names

• Master node name – k8master
• Worker nodes name – knode1, knode2, knode3

Step 2: Update OS

Keep the OS Up to date

Run the below Command to update OS

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yum update -y

Step 3: Disable SElinux 

By disabling the SElinux, all containers can easily access the host filesystem.

We can Disable SElinux by two methods

1. Run the below command

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setenforce 0

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

2. Go to SELinux configuration file and disable it

Run the below command

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nano /etc/sysconfig/selinux and type SELINUX=disabled

Step 4: Disable or Off the SWAP

By disabling the SWAP, kubelet will work perfectly.

Run the below command to disable SWAP:

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swapoff -a && sed -i '/swap/d' /etc/fstab

Step 5: To Allow Ports in Firewall or Disable Firewall

By allowing the below ports or disabling firewall, all containers, network drivers, and pods are communicating across the kubernetes cluster properly

Run the following command to allow ports in firewall:

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firewall-cmd --permanent --add-port=6443/tcp

firewall-cmd --permanent --add-port=2379-2380/tcp

firewall-cmd --permanent --add-port=10250/tcp

firewall-cmd --permanent --add-port=10251/tcp

firewall-cmd --permanent --add-port=10252/tcp

firewall-cmd --permanent --add-port=10255/tcp

firewall-cmd –-reload

Run the below command to disable firewall (This step is not recommended for production environment, but in this article, we are going to do disable firewall)

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systemctl stop firewalld

systemctl disable firewalld

Step 6: To update the IP Tables run the following command

By updating IP Tables, Port forwarding and Filtering process will work perfectly

Run the below command to update the IP tables:

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modprobe br_netfilter

echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables

Step 7: To Install Docker and Kubernetes in nodes, need to configure docker and Kubernetes repositories

Kubernetes: - Run the below command to add Kubernetes repo

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nano /etc/yum.repos.d/kubernetes.repo

Paste the below details in nano editor

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[kubernetes]

name=Kubernetes

baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64

enabled=1

gpgcheck=1

repo_gpgcheck=1

gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg

        https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg

You can see below screenshot I have added the above details in all four VM’s and save the file

Docker:- Run the below command to add docker repo

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

To download external packages:- Run the below command to get all docker and Kubernetes packages from docker and google repos without any issues

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subscription-manager repos --enable=rhel-7-server-extras-rpms

Up to this, you can see all the steps in below snap.

Step 8: To install the docker and Kubernetes components

Run the following command to install the Kubenetes/Docker (kublet kubeadm kubectl docker)

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yum install kubelet kubeadm kubectl docker -y

Step 9: To start and enable Kubernetes and docker services

Run the below commands to start:

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systemctl start docker && systemctl enable docker

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systemctl start kubelet && systemctl enable kubelet

Step 10: To run cluster configuration in Master node, this step should follow only in master node

Run the below command to start cluster configuration in master node

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kubeadm init --apiserver-advertise-address=10.1.5.46 --ignore-preflight-errors all --pod-network-cidr=10.244.0.0/16 --token-ttl 0

apiserver address must be masternode IP (10.1.5.46) address

You can see the below output

After the successful start of kubadm master, we need to run the above-shown command from the non-root or root user then only a user can control the kubectl commands.

Run the command

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mkdir -p $HOME/.kube

sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

Run the command

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sudo chown $(id -u):$(id -g) $HOME/.kube/config

Step 11: To check the all pods are running successful in cluster 

Run the command you can see all pods in namespaces

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kubectl get pods –all-namespaces

You can see the coredns service not yet started, still in pending, So that we need to install flannel network plugin to run coredns to start pod network communication.

Step 12: To Install Flannel Pod network driver

Run the below command to install POD network

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kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Now you can see coredns and all pods in namespaces are in ready and running successfully.

Step 13: To Taint master node as a Master 

Run the below command to taint the master node and make as a master.

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kubectl taint nodes --all node-role.kubernetes.io/master-

Step 14: Join the Worker Nodes to Master Node.

Run the token which produced by master node in other nodes to join to the cluster. 

Generated Token:-

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kubeadm join 10.1.5.46:6443 –token lixbn2.aea4n63ypd42578

Run the command to check all the nodes are connected to cluster or not

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Kubectl get nodes

Step 15: To Install and configure Kubernetes Dashboard

Run the Below Command to install the dashboards

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kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.0.0-beta8/aio/deploy/recommended.yaml

Create a service account dashboard(username) for dashboard to access it

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kubectl create serviceaccount dashboard -n default

Run the Below command to give admin access to user(dashboard) to bind with cluster for accessing dashboard.

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kubectl create clusterrolebinding dashboard-admin -n default  --clusterrole=cluster-admin --

serviceaccount=default:dashboard

Run the below command to generate the secret key for user(dashboard), to access Kubernetes dashboard

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kubectl get secret $(kubectl get serviceaccount dashboard -o jsonpath="{.secrets[0].name}") -o jsonpath="{.data.token}" | base64 --decode

You can see the generated key below, copy and save it.

To start the dashboard service, Run the below command.

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kubectl proxy

Paste and Go to the below URL in Master Node and click the token radio button and then paste the generated access token.

http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/.

After signing in you can see the Kubernetes dashboard

In the end, we completed our Kubernetes cluster configuration setup successfully.

I hope you love this article; please share and like it.

Cheers,

Gokulakrishna