Kubernetes Notes

Installation Instructions

CentOS Installation

Prerequisites : Kubernetes will not install if you have swap running, so we need to turn that off: - sudo swapoff -a - In /etc/fstab, comment out line /root/swap swap swap sw 0 0

1. Install Docker

   1.1. yum update -y && yum install -y docker 1.2 systemctl enable docker

2. Install Kubernetes

   2.1 Add Kubernetes Repository Key

    cat <<EOF > /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
   

   2.2 Turn off SELINUX

   • setenforce 0
   • In /etc/selinux/config, change from SELINUX=enforcing to SELINUX=permissive

   2.3 Install Kubernetes packages

   • yum install -y kubelet kubeadm kubectl

   2.4 Start Kubernetes service and persist on reboot

   • systemctl enable kubelet && systemctl start kubelet

   2.5 Apply Network Settings for Pod Intercommunication

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

   2.6 Apply Changes

   • sysctl --system

3. Configure Kubernetes

   3.1 kubeadm init--pod-network-cidr=10.255.0.0/16

   3.2 Make a note of the code that you'll need to run on your Worker nodes to join them to the cluster. It will look something like this

   • kubeadm join 172.31.25.30:6443 --token z7lmk4.v3fhppz3xg63c7uy --discovery-token-ca-cert-hash sha256:e458b4b0519674db89f4678315f11dc29366b0c7d5c7eb43d9125d5838f55e19

   3.3 Create and Configure Kubernetes Home Directory

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

4. Install Flannel for Pod Networking

   4.1 kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.yml

5. Confirm Your Master Node is Online

   5.1 kubectl get nodes

   • You should see the Hostname of your server in Master Role and Ready status.

Firewall Rules

Master Nodes

Protocol	Port	Program
TCP	6443*	Kubernetes API Server
TCP	2379-2380	etc Server Client API
TCP	10250	Kubelet API
TCP	10251	kube-scheduler
TCP	10252	kube-controller-manager
TCP	10255	Read-Only Kubelet API

Worker Nodes

Protocol	Port	Program
TCP	10250	Kubelet API
TCP	10255	Read-Only Kubelet api
TCP	30000-32767	NodePort Services