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

1. Preparation

1.1 Host Planning

master  192.168.100.101  CentOS7  2*2  50G
node1   192.168.100.102  CentOS7  2*2  50G
node2   192.168.100.103  CentOS7  2*2  50G

1.2 Upgrade Kernel Version

Reference: https://www.cnblogs.com/wangyuanguang/p/18051798

1.3 Set Hostname and Hosts Mapping

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. Deploy Docker

2.1 Docker Daemon Configuration (example)

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. Deploy Kubernetes Base Commands

3.1 Add Alibaba Cloud yum repo for k8s

cat > /etc/yum.repos.d/kubernetes.repo <<EOF
[kubernetes]
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 List Available Packages

yum --disablerepo="*" --enablerepo="kubernetes" list available

3.3 Install kubeadm, kubectl, kubelet

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

4. Deploy Cluster

4.1 Initialize Master

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

Parameter notes:

--apiserver-advertise-address   Specify the master interface for cluster communication.
--pod-network-cidr               CIDR for the pod network (Flannel example: 10.240.0.0/16).
--service-cidr                   CIDR for the service network.
--image-repository               Use a domestic mirror for Kubernetes images.
--kubernetes-version            Pin a specific version to avoid network lookups.

4.2 Error Handling

Problem 1: container runtime not running (containerd CRI not implemented).

# Edit /etc/containerd/config.toml and comment out the line:
#disabled_plugins = ["cri"]
# Then restart containerd and re‑run kubeadm init.

Problem 2: Re‑initializing after a failed init leaves manifest files. kubeadm reset Problem 3: Missing bridge netfilter sysctl. modprobe br_netfilter Problem 4: kubelet timeout waiting for control‑plane.

# Ensure the pause image is available, e.g.:
sandbox_image = "registry.aliyuncs.com/google_containers/pause:3.6"
systemctl daemon-reload
systemctl restart containerd.service

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 jcdduw.3wfskykjk7gwdf1u \
  --discovery-token-ca-cert-hash sha256:dd3cb5208a4ca032e85a5a30b9b02f963aff2fece13045cf8c74d7b9ed7f6098

4.5 Remove a Node

# Drain the node
kubectl drain node2 --delete-local-data --force --ignore-daemonsets
# Delete the node object
kubectl delete node node2
# On the removed node, clean up:
kubeadm reset -f

5. Install CNI Network Plugin

Choose one of the following (Flannel is recommended on cloud VMs).

5.1 Install Flannel

mkdir /data/k8s && cd /data/k8s
wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
# Adjust the pod network CIDR if needed
sed -i 's/10.244.0.0/10.240.0.0/' kube-flannel.yml
kubectl apply -f kube-flannel.yml

Verify pods are running:

kubectl get pods -n kube-flannel

6. Cluster Testing

# Create a test deployment
kubectl create deployment nginx --image=nginx
# Expose it as NodePort
kubectl expose deployment nginx --port=80 --type=NodePort
# Verify services on all nodes
kubectl get svc

Check the service from the other nodes as well.

7. Common kubectl Commands

# List resources
kubectl get <component>   # e.g., kubectl get pod
# Apply a yaml file or directory
kubectl apply -f xxx.yaml
# Delete resources defined in a yaml file
kubectl delete -f xxx.yaml
# Describe a pod for detailed status
kubectl describe pod <pod-name>
# View pod logs
kubectl logs <pod-name>
# Show resource usage
kubectl top node   # or kubectl top pod
# Exec into a pod
kubectl exec -ti <pod-name> -- /bin/bash