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Creating a Kubernetes Cluster

Hands-On Lab

 

Photo of Michael McClaren

Michael McClaren

Linux Training Architect I in Content

Length

01:30:00

Difficulty

Beginner

In this hands-on lab, we will install and configure a Kubernetes cluster consisting of 1 master and 2 nodes. Once the installation and configuration are complete, we will have a 3-node Kubernetes cluster that uses Flannel as the network overlay.

What are Hands-On Labs?

Hands-On Labs are scenario-based learning environments where learners can practice without consequences. Don't compromise a system or waste money on expensive downloads. Practice real-world skills without the real-world risk, no assembly required.

Creating a Kubernetes Cluster

Introduction

In this hands-on lab, we will install and configure a Kubernetes cluster consisting of 1 master and 2 nodes. Once the installation and configuration are complete, we will have a 3-node Kubernetes cluster that uses Flannel as the network overlay.

Logging In

Use the credentials provided on the hands-on lab overview page to log into the master and server nodes as cloud_user. It's probably a good idea to have three terminals open, one for each node.

Install Docker and Kubernetes on All Servers

Most of these commands need to be run on each of the nodes. Pay attention though. Down at Step 10, we are going to do a little bit on just the master, and down at Step 15 we'll run something on just the nodes. There are notes down there, just be watching for them.

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

    sudo su  
  2. Disable SELinux:

    setenforce 0
    sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux
  3. Enable the br_netfilter module for cluster communication:

    modprobe br_netfilter
    echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables
  4. Ensure that the Docker dependencies are satisfied:

    yum install -y yum-utils device-mapper-persistent-data lvm2
  5. Add the Docker repo and install Docker:

    yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
    yum install -y docker-ce
  6. Set the cgroup driver for Docker to systemd, reload systemd, then enable and start Docker:

    sed -i '/^ExecStart/ s/$/ --exec-opt native.cgroupdriver=systemd/' /usr/lib/systemd/system/docker.service
    systemctl daemon-reload
    systemctl enable docker --now
  7. Add the Kubernetes repo:

    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=0
    repo_gpgcheck=0
    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 Kubernetes:

    yum install -y kubelet kubeadm kubectl
  9. Enable the kubelet service. The kubelet service will fail to start until the cluster is initialized, this is expected:

    systemctl enable 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://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
  5. Check the cluster state:

    kubectl get pods --all-namespaces

    Note: Complete the following steps on the NODES ONLY!

  6. 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

Create and Scale a Deployment Using kubectl

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

Conclusion

We got it done. We've created Kubernetes cluster, and deployed Nginx on it. Then we scaled up to four pods. Congratulations!