How to Build a Fully Functional Kubernetes Cluster on CentOS 7 in Minutes

Installation requirements and environment preparation for a Kubernetes cluster on CentOS 7.6.

# System: centos7.6
# Hardware: 2 CPU, 2G RAM
# Internet access, swap disabled
# Docker pre-installed

Prepare three servers

Server IPs and names:

192.168.106.102 – k8s-master

192.168.106.103 – k8s-node01

192.168.106.104 – k8s-node02

Initialize system environment (run on all three servers)

1.1 Disable firewall

systemctl stop firewalld
systemctl disable firewalld

1.2 Disable SELinux and swap

sed -i 's/enforcing/disabled/' /etc/selinux/config
setenforce 0
swapoff -a  # temporary; permanent requires editing fstab

1.3 Set hostnames and update /etc/hosts

hostnamectl set-hostname K8S-master   # on master (102)
hostnamectl set-hostname K8S-node01   # on node01 (103)
hostnamectl set-hostname K8S-node02   # on node02 (104)

cat >> /etc/hosts <<EOF
192.168.106.102 K8S-master
192.168.106.103 K8S-node01
192.168.106.104 K8S-node02
EOF

1.4 Enable bridge traffic to iptables

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

1.5 Sync time

ntpdate time.windows.com
cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime

1.6 Configure Alibaba Cloud yum repo and install Kubernetes packages

cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64/
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF

yum install -y kubelet-1.18.0 kubeadm-1.18.0 kubectl-1.18.0
systemctl enable kubelet

Deploy Kubernetes master node

kubeadm init \
  --apiserver-advertise-address=192.168.106.102 \
  --image-repository registry.aliyuncs.com/google_containers \
  --kubernetes-version v1.18.0 \
  --service-cidr=10.96.0.0/12 \
  --pod-network-cidr=10.244.0.0/16

Copy the kubeadm join command shown at the end of the init output to add worker nodes.

Install pod network plugin (Flannel)

wget http://120.78.77.38/file/kube-flannel.yaml
kubectl apply -f kube-flannel.yaml
# Alternatively pull the image first
docker pull lizhenliang/flannel:v0.11.0-amd64
kubectl apply -f kube-flannel.yaml
kubectl get pods -n kube-system

Add worker nodes to the master

kubeadm join 192.168.106.102:6443 --token 7w0oxu.drdkjuzirow3dvj7 \
  --discovery-token-ca-cert-hash sha256:e30452be8217affa2f11229e45cb2ed9dfa4424c82d5f354d9813ce789f58fdb

Verify cluster

kubectl get nodes
kubectl get pods -n kube-system

Install Kubernetes dashboard

wget http://120.78.77.38/file/kubernetes-dashboard.yaml
kubectl apply -f kubernetes-dashboard.yaml
kubectl get pods -n kubernetes-dashboard
kubectl get pod -n kubernetes-dashboard -o wide

Access the dashboard at https://192.168.106.104:30001 using Firefox, create a service account and cluster role binding to obtain a token, then log in.