kubernets cluster

Kubernetes is an open source container orchestration system that helps users automate the management of multiple containerized applications. This article will introduce how to deploy a Kubernetes cluster on a CentOS server.

Environmental preparation

1. Install Docker

Install Docker on all nodes.

sudo yum install -y docker

sudo systemctl start docker

sudo systemctl enable docker

 

2. Install kubeadm

Install kubeadm, kubelet and kubectl on all nodes.

sudo tee /etc/yum.repos.d/kubernetes.repo <<EOF
[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
EOF

sudo yum install -y kubelet kubeadm kubectl

sudo systemctl start kubelet

sudo systemctl enable kubelet

3. Close the swap partition

Kubernetes does not support the use of swap partitions, so swap needs to be turned off.

sudo swapoff -a

sudo sed -i '/swap/d' /etc/fstab

 

Initialize the Kubernetes master node

Initialize the Kubernetes cluster on the master node.

sudo kubeadm init --pod-network-cidr=10.244.0.0/16

After the command is executed, it will output information similar to the following:

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.0.10:6443 --token abcdef.1234567890abcdef \
    --discovery-token-ca-cert-hash sha256:0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef

Copy sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/configthe output of the command and execute it on the local machine.

ssh user@master_ip sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

 Then install the pod network plugin on your local machine.

kubectl apply -f https://docs.projectcalico.org/v3.14/manifests/calico.yaml

 After the master node is initialized, you can use the following command to view the status:

kubectl get nodes

Join a Kubernetes worker node

Execute the following command on the server that needs to be added as a working node:

sudo kubeadm join 192.168.0.10:6443 --token abcdef.1234567890abcdef \
    --discovery-token-ca-cert-hash sha256:0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
 

 

where 192.168.0.10is the IP address of the master node, and the details of the join command have been output when the master node is initialized.

After the worker node joins, you can use the following command to view the status:

kubectl get nodes

 

deploy application

Now the Kubernetes cluster is ready to deploy applications. Here is a simple Nginx example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - containerPort