In this post we’ll go through step by step instructions on how to setup a multi-node Kubernetes cluster. We’ll be using centos vm’s for the purpose of this post
Setting up the Master node
1 – Disable swap
The idea of kubernetes is to tightly pack instances to as close to 100% utilized as possible. All deployments should be pinned with CPU/memory limits. So if the scheduler sends a pod to a machine it should never use swap at all. You don’t want to swap since it’ll slow things down.
swapoff -a
2 – Remove the swap reference from the fstab file (/etc/fstab)
#/root/swap swap swap sw 0 0
3 – Disable SELinux enforcement
setenforce 0
4 – Change SELinux to permissive (/etc/selinux/config)
SELINUX=permissive
5 – Install Docker
sudo yum install -y docker
6 – Start and Enable docker
systemctl start docker systemctl enable docker
7 – Create the kubernetes repo file
cat < /etc/yum.repos.d/kubernetes.repo [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
8 – Install the kubernetes packages kubelet, kubeadm,
kubectl
sudo yum install -y kubelet kubeadm kubectl
9 – Start and Enable kubelet
systemctl enable kubelet systemctl start kubelet
10 – Network changes for containers
cat < /etc/sysctl.d/k8s.conf net.bridge.bridge-nf-call-ip6tables = 1 net.bridge.bridge-nf-call-iptables = 1 EOF
11 – And for the above network setting to take place execute the below command
sysctl --system
12 – Set the pod network CIDR
kubeadm init --pod-network-cidr=10.244.0.0/16
Your Kubernetes master 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/ You can now join any number of machines by running the following on each node as root: kubeadm join --token 6065d6.90ab98e756bd01b3 172.31.123.145:6443 --discovery-token-ca-cert-hash sha256:611b3df6515064293e1a8c7583a64f9d72e660c68011d981d6759b7017311c7b
note down the above token command which will be later used on the worker nodes to join this master
Set the proper permissions to the kube config
mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config
13 – Apply ip address to containers using flannel(flannel is a virtual network that attaches IP addresses to containers)
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.yml
Check the nodes using kubectl
[root@nikhitkumar4 user]# kubectl get nodes NAME STATUS ROLES AGE VERSION nikhitkumar4.server.com Ready master 2d v1.9.2
Our master is ready.
Now that our master node is ready lets set up our worker node. Follow the same steps on the worker nodes. once you have completed running all the above steps on the worker nodes. run the kube join command that you got from the master in all the worker nodes
kubeadm join --token 6065d6.90ab98e756bd01b3 172.31.123.145:6443 --discovery-token-ca-cert-hash sha256:611b3df6515064293e1a8c7583a64f9d72e660c68011d981d6759b7017311c7b
Then check the kubectl get nodes command to check the nodes connected
[root@nikhitkumar4 user]# kubectl get nodes NAME STATUS ROLES AGE VERSION nikhitkumar4.server.com Ready master 16d v1.9.2 nikhitkumar5.server.com NotReady 16d v1.9.2
We have completely set up our kubernetes multinode cluster
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