Creating a Kubernetes Cluster

Most commands need to be run on all nodes. Pay attention though. Commands to initialize and configure the cluster need to be run only on the master node, whereas kubeadm join commands need to be run only on node1 and node2. There are notes down there, just watch for them.

1. Once we have logged in, we need to elevate privileges using sudo:

   sudo su  
   

2. Create the configuration file for containerd:

   cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf
   overlay
   br_netfilter
   EOF
   

3. Load the modules:

   sudo modprobe overlay
   sudo modprobe br_netfilter
   

4. Set the system configurations for Kubernetes networking:

   cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
   net.bridge.bridge-nf-call-iptables = 1
   net.ipv4.ip_forward = 1
   net.bridge.bridge-nf-call-ip6tables = 1
   EOF
   

5. Apply the new settings:

   sudo sysctl --system
   

6. Add the stable Docker Community Edition repository to yum:

   yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
   

7. Install containerd:

   sudo yum install -y containerd.io
   

8. Create the default configuration folder for containerd:

   sudo mkdir -p /etc/containerd
   

9. Generate the default containerd configuration, and save it to the newly created default file:

   sudo containerd config default | sudo tee /etc/containerd/config.toml
   

10. Restart containerd to ensure the new configuration file is used:

    sudo systemctl restart containerd
    

11. Verify that containerd is running:

    sudo systemctl status containerd
    

12. Disable swap:

    sudo swapoff -a
    

13. Set SELinux in permissive mode (effectively disabling it):

     sudo setenforce 0
     sudo sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config
    

14. Add the Kubernetes repository (this overwrites any existing configuration in /etc/yum.repos.d/kubernetes.repo):

    cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
    [kubernetes]
    name=Kubernetes
    baseurl=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/
    enabled=1
    gpgcheck=1
    gpgkey=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/repodata/repomd.xml.key
    exclude=kubelet kubeadm kubectl cri-tools kubernetes-cni
    EOF
    

15. Install kubelet, kubeadm and kubectl:

    sudo yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
    

16. Enable the kubelet service before running kubeadm:

    sudo systemctl enable --now kubelet
    

Note: Complete the following section on the MASTER ONLY!

1. Initialize the cluster using the IP range for Flannel:

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

2. Copy the kubeadmn join command that is in the output. We will need this later.

3. Exit sudo, copy the admin.conf to your home directory, and take ownership:

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

4. Deploy Flannel:

   kubectl apply -f https://github.com/flannel-io/flannel/releases/latest/download/kube-flannel.yml
   

5. Check the cluster state:

   kubectl get pods --all-namespaces
   

Note: Complete the following steps on the NODES ONLY!

1. Run the join command that you copied earlier, this requires running the command prefaced with sudo on the nodes (if we hadn't run sudo su to begin with). Then we'll check the nodes from the master.

   kubectl get nodes
   

Note: These commands will only be run on the master node.

1. Create a simple deployment:

   kubectl create deployment nginx --image=nginx
   

2. Inspect the pod:

   kubectl get pods
   

3. Scale the deployment:

   kubectl scale deployment nginx --replicas=4
   

4. Inspect the pods. We should have four now:

   kubectl get pods