Steps to install kubernetes cluster manually using CENTOS 7
In this blog, we will show you the Steps to install kubernetes cluster manually using CENTOS 7.
REQUIREMENTS
- 3 Virtual Machine with an internet connection.
- Kubenetes components
OVERVIEW
- Please check the URL https://blog.assistanz.com/google-kubernetes-overview-and-architecture/ to know more about the kubernetes basics and it’s architecture.
INFRASTRUCTURE OVERVIEW
- We are creating two node cluster for this demo.
- The Master IP will be 192.168.3.81.
- Node 1 IP will be 192.68.3.82 and Node 2 IP will be 192.168.3.83.
- We are using the Flannel Network for the POD communication in this demo.
Note: The VM IP’s may change based on your environment
MASTER SERVER CONFIGURATION
- Log in to the master server and we have already set the hostname as k8s-master during OS installation.
- Disable the SELinux using the below commands.
exec bash
setenforce 0
sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux
- Open the sysctl.conf file.
vi /etc/sysctl.conf
- Add the below entries in the conf file to change the Linux host bridge values and save the changes.
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
- open the fstab file.
vi /etc/fstab
- Disable the SWAP by adding the # symbol at the beginning and save the changes.
.
- Restart the VM using the command init 6 to apply the SELinux and SWAP changes.
- Once the VM is back to online, open the host file.
vi /etc/hosts
- Add the below entries in the host file and save the changes.
192.168.3.81 k8s-master
192.168.3.82 k8s-node1
192.168.3.83 k8s-node2
Note: The IP’s may change based on your environment
- Create a new file named kubernetes.repo under yum.repos.d folder using the below command.
vi /etc/yum.repos.d/kubernetes.repo
- Add the below entries and save the changes.
[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
INSTALLING DOCKER AND KUBEADM
- Now, Install the docker and kubeadm using the below command.
yum install -y kubeadm docker
- It will take few minutes to complete the installation.
- Enable and start the docker and kubelet services using commands.
systemctl enable docker && systemctl enable kubelet
systemctl start docker && systemctl start kubelet
NODE(S) CONFIGURATION
- We have already set the hostname for node1 and node2 during OS installation.
- Please follow the above master server configuration steps for the kubernetes node preparation. We have already installed the docker and kubeadm on both the nodes.
CREATING CLUSTER
- We are using the Flannel network for this demo.
- To make the flannel to working properly, we need to specify the network CIDR while configuring the cluster. Use the below command to create a cluster.
kubeadm init --pod-network-cidr=10.244.0.0/16
- It will take few minutes to complete the configuration process.
- Kubernetes cluster has configured successfully.
- Execute the below commands below start using the cluster.
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
- Also, make a note of the kubeadm join command to add the nodes into the cluster.
- We can list the available system PODS using the below command.
kubectl get pods --all-namespaces
- Kube-DNS will be in pending state until we install the POD network for the cluster.
INSTALLING NETWORK
- Use the below command to install the Flannel network.
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.yml
- It will take few minutes to complete the installation.
- The flannel pod will start initiating and it will take few minutes to complete the configuration process.
- We can get the detailed information about a POD using describe option.
kubectl describe pod <pod name> --namespace=kube-system
- After some time, all the system pods are in running state.
ADDING NODES TO THE CLUSTER
- From the node1 use the kubeadm join command to add the nodes into the cluster.
kubeadm join --token 878914.4587d610b5478141 192.168.3.81:6443 --discovery-token-ca-cert-hash sha256:6a23a6a7be997625f53e564a8b510627d035b000f9c288f7487fc9415c3338f1
Note: Token ID,IP and sha256 details will vary based on your environment
- Node has been joined into the cluster successfully.
VERIFICATION
- From the master server, type the below command to list the available nodes in the cluster.
kubectl get nodes
- We can use the same kubeadm join command to add more nodes in future.
TIP
- In case if you forget to make a note of kubeadm join information, use the below command from the master server to retrieve the join information.
kubeadm token create --print-join-command
EXTERNAL LINKS
https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/
VIDEO
Thanks for reading this blog. We hope it was useful for you to learn about installing kubernetes manually on CENTOS 7.
