Step‑by‑Step Guide to Deploy a Kubernetes Cluster on CentOS 7

1. Preparation

1.1 Host Planning

Define three hosts (master, node1, node2) with IP 192.168.100.101‑103, CentOS 7, 2 CPU × 2 GB RAM, 50 GB disk.

1.2 Upgrade Kernel

Refer to https://www.cnblogs.com/wangyuanguang/p/18051798 for kernel upgrade.

1.3 Set Hostname and /etc/hosts

hostnamectl set-hostname master
hostnamectl set-hostname node1
hostnamectl set-hostname node2
vim /etc/hosts
192.168.100.101 master
192.168.100.102 node1
192.168.100.103 node2

1.4 Disable SELinux and firewalld

systemctl stop firewalld
systemctl disable firewalld
sed -i 's/enforcing/disabled/' /etc/selinux/config
setenforce 0

1.5 Disable swap

swapoff -a

1.6 Enable bridge‑netfilter

cat > /etc/sysctl.d/k8s.conf <<EOF
net.ipv4.ip_forward = 1
net.ipv4.tcp_tw_recycle = 0
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system

2. Install Docker

2.1 Configure daemon

vim /etc/docker/daemon.json
{
  "registry-mirrors": [
    "https://hub-mirror.c.163.com",
    "https://registry.aliyuncs.com",
    "https://registry.docker-cn.com",
    "https://docker.mirrors.ustc.edu.cn"
  ],
  "data-root": "/data/docker",
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": { "max-size": "300m","max-file": "3" },
  "live-restore": true
}

3. Install Kubernetes components

3.1 Add Alibaba Cloud yum repo

cat > /etc/yum.repos.d/kubernetes.repo <<EOF
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF

3.2 Install kubeadm, kubelet, kubectl

yum install -y kubelet-1.28.2 kubeadm-1.28.2 kubectl-1.28.2
systemctl start kubelet
systemctl enable kubelet

4. Initialize the cluster

4.1 Master initialization

kubeadm init \
  --apiserver-advertise-address=192.168.100.101 \
  --image-repository registry.aliyuncs.com/google_containers \
  --kubernetes-version v1.28.0 \
  --service-cidr=10.140.0.0/16 \
  --pod-network-cidr=10.240.0.0/16

Parameters: --apiserver-advertise-address selects the master NIC; --pod-network-cidr matches the CNI plugin (Flannel uses 10.240.0.0/16); --service-cidr defines the service network; --image-repository points to a domestic mirror; --kubernetes-version pins the version.

4.2 Common errors and fixes

Four typical pre‑flight or post‑init issues are described with solutions: (1) container runtime not running – edit /etc/containerd/config.toml to enable the cri plugin; (2) leftover manifests after a failed init – run kubeadm reset; (3) missing bridge‑nf‑call‑iptables – load br_netfilter module; (4) kubelet not starting – ensure the pause image is available and restart containerd.

4.3 Configure kubectl

mkdir -p $HOME/.kube
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config
# for root users
echo "export KUBECONFIG=/etc/kubernetes/admin.conf" > /etc/profile.d/kubeconfig.sh
source /etc/profile.d/kubeconfig.sh

4.4 Join worker nodes

kubeadm join 192.168.100.101:6443 \
  --token <TOKEN> \
  --discovery-token-ca-cert-hash sha256:<HASH>

5. Install CNI plugin

5.1 Flannel

mkdir /data/k8s && cd /data/k8s
wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
sed -i 's/10.244.0.0/10.240.0.0/' kube-flannel.yml
kubectl apply -f kube-flannel.yml

6. Test the cluster

kubectl create deployment nginx --image=nginx
kubectl expose deployment nginx --port=80 --type=NodePort
kubectl get svc

7. Common kubectl commands

Examples include kubectl get pod -o wide -n namespace, kubectl apply -f xxx.yaml, kubectl delete -f xxx.yaml, kubectl describe pod pod-name, kubectl logs pod-name, kubectl top node|pod, and kubectl exec -ti pod-name /bin/bash for troubleshooting and resource inspection.