Master Node<\/strong> \u2013 This machine generally acts as the control plane and runs the cluster database and the API server (which the kubectl CLI communicates with).<\/p>\n\n\n\n Our 3-node Kubernetes Cluster<\/strong> will look something like this:<\/p>\n\n\n\n For Kubernetes<\/strong> to work, you will need a containerization engine. As mentioned, we will be using Docker-CE<\/strong>.<\/p>\n\n\n\n The following institutions will be performed on CentOS 8 Master-Node<\/strong>.<\/p>\n\n\n\n On your CentOS 8 Master-Node<\/strong>, set the system hostname and update DNS in your \/etc\/hosts<\/strong> file.<\/p>\n\n\n\n Next, ping your worker-node-1<\/strong> and worker-node-2<\/strong> to check if your updated host file is working correctly using the ping command.<\/p>\n\n\n\n Next, disable Selinux<\/strong>, as this is required to allow containers to access the host filesystem, which is needed by pod networks and other services.<\/p>\n\n\n\n Setting setenforce<\/strong> to Kubernetes makes use of various ports for communication and access and these ports need to be accessible to Kubernetes and not limited by the firewall.<\/p>\n\n\n\n Configure the firewall rules on the ports.<\/p>\n\n\n\n You will need to add the Docker<\/strong> repository first as it is no longer in the default package list using the following dnf config-manager<\/strong> command.<\/p>\n\n\n\n Also install containerd.io<\/strong> package which is available as a daemon that manages the complete container lifecycle of its host system, from image transfer and storage to container execution and supervision to low-level storage to network attachments and beyond.<\/p>\n\n\n\n Now install the latest version of a docker-ce<\/strong> package.<\/p>\n\n\n\n You can now enable and start the docker service.<\/p>\n\n\n\n Next, you will need to add Kubernetes<\/strong> repositories manually as they do not come installed by default on CentOS 8<\/strong>.<\/p>\n\n\n\n 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<\/p>\n\n\n\n Kubeadm<\/strong> helps you bootstrap a minimum viable Kubernetes cluster that conforms to best practices. With kubeadm<\/strong>, your cluster should pass the Kubernetes Conformance tests.<\/p>\n\n\n\n Kubeadm<\/strong> also supports other cluster lifecycle functions, such as upgrades, downgrade, and managing bootstrap tokens. Kubeadm is also integration-friendly with other orchestration tools like Ansible<\/strong> and Terraform<\/strong>.<\/p>\n\n\n\n With the package repo now ready, you can go ahead and install kubeadm<\/strong> package.<\/p>\n\n\n\n When the installation completes successfully, enable and start the service.<\/p>\n\n\n\n The Kubernetes master which acts as the control plane<\/strong> for the cluster runs a few critical services necessary for the cluster. As such, the initialization process will do a series of prechecks to ensure that the machine is ready to run Kubernetes. These prechecks expose warnings and exit on errors. kubeadm init<\/strong> then downloads and installs the cluster control plane components.<\/p>\n\n\n\n Now it\u2019s time to initialize Kubernetes master, but before that, you must disable swap in order to run \u201ckubeadm init<\/strong>\u201c command.<\/p>\n\n\n\n Initializing Kubernetes<\/strong> master is a completely automated process that is controlled by the \u201ckubeadm init<\/strong>\u201c command as shown.<\/p>\n\n\n\n Next, copy the following command and store it somewhere, as we required to run this command on the worker nodes later.<\/p>\n\n\n\n Tip<\/strong>: Sometimes the above command might throw errors about the arguments passed, so to avoid errors, you need to remove the Once Kubernetes<\/strong> initialized successfully, you must enable your user to start using the cluster. In our scenario, we will be using the root user. You can also start the cluster using sudo user as shown.<\/p>\n\n\n\n To use root<\/strong>, run:<\/p>\n\n\n\n To use a sudo enabled user<\/strong>, run:<\/p>\n\n\n\n Now confirm that the kubectl command<\/strong> is activated.<\/p>\n\n\n\n At this moment, you will see the status of the master-node is \u2018NotReady<\/strong>\u2019. This is because we are yet to deploy the pod network to the cluster.<\/p>\n\n\n\n The pod Network is the overlay network for the cluster, that is deployed on top of the present node network. It is designed to allow connectivity across the pod.<\/p>\n\n\n\n Deploying the network cluster is a highly flexible process depending on your needs and there are many options available. Since we want to keep our installation as simple as possible, we will use Weavenet<\/strong> plugin which does not require any configuration or extra code and it provides one IP address per pod which is great for us.<\/p>\n\n\n\n These commands will be important to get the pod network setup.<\/p>\n\n\n\n Now if you check the status of your master-node, it should be \u2018Ready<\/strong>\u2019.<\/p>\n\n\n\n Next, we add the worker nodes<\/strong> to the cluster.<\/p>\n\n\n\n The following instructions will be performed on each worker node<\/strong> when joining the Kubernetes cluster.<\/p>\n\n\n\n First set the hostname on your worker-node-1<\/strong> and worker-node-2<\/strong>, and then add the host entries to the \/etc\/hosts<\/strong> file.<\/p>\n\n\n\n Next, ping your master node<\/strong> from your worker nodes<\/strong> to confirm that your updated host file is working fine using the ping command.<\/p>\n\n\n\n Next, disable SElinux<\/strong> and update your firewall rules.<\/p>\n\n\n\n Add the Docker repository first using DNF config-manager.<\/p>\n\n\n\n Next, add the containerd.io<\/strong> package.<\/p>\n\n\n\n With these two packages installed, install the latest version of docker-ce<\/strong>.<\/p>\n\n\n\n Enable and start the docker service.<\/p>\n\n\n\n You will need to add Kubernetes<\/strong> repositories manually as they do not come pre-installed on CentOS 8<\/strong>.<\/p>\n\n\n\n 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<\/p>\n\n\n\n With the package repo now ready, you can go ahead and install kubeadm<\/strong>.<\/p>\n\n\n\n Start and enable the service.<\/p>\n\n\n\n We now require the token that kubeadm init<\/strong> generated, to join the cluster. You can copy and paste it to your node-1<\/strong> and node-2<\/strong> if you had copied it somewhere.<\/p>\n\n\n\n As suggested on the last line, go back to your master-node<\/strong> and verify if worker node-1<\/strong> and worker node-2<\/strong> have joined the cluster using the following command.<\/p>\n\n\n\n If all the steps run successfully, then, you should see node-1<\/strong> and node-2<\/strong> in ready status on the master-node<\/strong>. At this point, you have now successfully deployed a Kubernetes cluster on CentOS 8<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":" Logical Architecture Our installation is designed to have the Master-Node controlling the Worker Nodes. At the end of this installation, our logical architecture will look something like this. Master Node \u2013 This machine generally acts as the control plane and runs the cluster database and the API server (which the kubectl CLI communicates with). Our 3-node Kubernetes Cluster will look something […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[78,77,82,79,13],"tags":[],"class_list":["post-3131","post","type-post","status-publish","format-standard","hentry","category-containers","category-devops","category-docker","category-kubernetes","category-linux"],"_links":{"self":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts\/3131","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3131"}],"version-history":[{"count":4,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts\/3131\/revisions"}],"predecessor-version":[{"id":3160,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=\/wp\/v2\/posts\/3131\/revisions\/3160"}],"wp:attachment":[{"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3131"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3131"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/microsoftgeek.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3131"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Kubernetes](\"https:\/\/www.tecmint.com\/wp-content\/uploads\/2020\/01\/Kubernetes-Cluster-Setup-Diagram.jpg\")
Installation of Kubernetes Cluster on Master-Node<\/h3>\n\n\n\n
Step 1: Prepare Hostname, Firewall, and SELinux<\/h4>\n\n\n\n
# hostnamectl set-hostname master-node\n# cat <<EOF>> \/etc\/hosts\n192.168.0.47 master-node\n192.168.0.48 node-1 worker-node-1\n192.168.0.49 node-2 worker-node-2\nEOF\n<\/pre>\n\n\n\n
# ping 192.168.0.48\n# ping 192.168.0.49\n<\/pre>\n\n\n\n
# setenforce 0\n<\/pre>\n\n\n\n
0<\/code> effectively sets SELinux to permissive, which effectively disables SELinux until the next reboot. To completely disable it, use the below command and reboot.<\/p>\n\n\n\n# sed -i --follow-symlinks 's\/SELINUX=enforcing\/SELINUX=disabled\/g' \/etc\/sysconfig\/selinux\n# reboot\n<\/pre>\n\n\n\n
![\"Kubernetes](\"https:\/\/www.tecmint.com\/wp-content\/uploads\/2020\/01\/Kubernetes-Ports.png\")
# firewall-cmd --permanent --add-port=6443\/tcp\n# firewall-cmd --permanent --add-port=2379-2380\/tcp\n# firewall-cmd --permanent --add-port=10250\/tcp\n# firewall-cmd --permanent --add-port=10251\/tcp\n# firewall-cmd --permanent --add-port=10252\/tcp\n# firewall-cmd --permanent --add-port=10255\/tcp\n# firewall-cmd --reload\n# modprobe br_netfilter\n# echo '1' > \/proc\/sys\/net\/bridge\/bridge-nf-call-iptables\n<\/pre>\n\n\n\n
Step 2: Install Docker-CE on CentOS 8<\/h4>\n\n\n\n
# dnf config-manager --add-repo=https:\/\/download.docker.com\/linux\/centos\/docker-ce.repo\n<\/pre>\n\n\n\n
# dnf install https:\/\/download.docker.com\/linux\/centos\/7\/x86_64\/stable\/Packages\/containerd.io-1.2.6-3.3.el7.x86_64.rpm\n<\/pre>\n\n\n\n
# dnf install docker-ce\n<\/pre>\n\n\n\n
# systemctl enable docker\n# systemctl start docker\n<\/pre>\n\n\n\n
Step 3: Install Kubernetes (Kubeadm) on CentOS 8<\/h4>\n\n\n\n
# cat <<EOF > \/etc\/yum.repos.d\/kubernetes.repo\n<\/pre>\n\n\n\n
# dnf install kubeadm -y \n<\/pre>\n\n\n\n
# systemctl enable kubelet\n# systemctl start kubelet\n<\/pre>\n\n\n\n
Step 4: Create a control-plane Master with kubeadm<\/h4>\n\n\n\n
# swapoff -a\n<\/pre>\n\n\n\n
# kubeadm init\n<\/pre>\n\n\n\n
![\"Initialize](\"https:\/\/www.tecmint.com\/wp-content\/uploads\/2020\/01\/Initialize-Kubernetes-Cluster-on-Master.png\")
kubeadm join 192.168.0.47:6443 --token nu06lu.xrsux0ss0ixtnms5 \\ --discovery-token-ca-cert-hash ha256:f996ea35r4353d342fdea2997a1cf8caeddafd6d4360d606dbc82314683478hjmf7<\/pre>\n\n\n\n
\u2018\\\u2019<\/code> character and your final command will look like this.<\/p>\n\n\n\n# kubeadm join 192.168.0.47:6443 --token nu06lu.xrsux0ss0ixtnms5 \u2013discovery token-ca-cert-hash sha256:f996ea35r4353d342fdea2997a1cf8caeddafd6d4360d606dbc82314683478hjmf7\n<\/pre>\n\n\n\n
# mkdir -p $HOME\/.kube\n# cp -i \/etc\/kubernetes\/admin.conf $HOME\/.kube\/config\n# chown $(id -u):$(id -g) $HOME\/.kube\/config\n<\/pre>\n\n\n\n
$ mkdir -p $HOME\/.kube\n$ sudo cp -i \/etc\/kubernetes\/admin.conf $HOME\/.kube\/config\n$ sudo chown $(id -u):$(id -g) $HOME\/.kube\/config\n<\/pre>\n\n\n\n
# kubectl get nodes\n<\/pre>\n\n\n\n
![\"Check](\"https:\/\/www.tecmint.com\/wp-content\/uploads\/2020\/01\/Check-Status-of-Nodes.png\")
Step 5: Setup Your Pod Network<\/h4>\n\n\n\n
# export kubever=$(kubectl version | base64 | tr -d '\\n')\n# kubectl apply -f \"https:\/\/cloud.weave.works\/k8s\/net?k8s-version=$kubever\"\n<\/pre>\n\n\n\n
![\"Setup](\"https:\/\/www.tecmint.com\/wp-content\/uploads\/2020\/01\/Setup-pod-network.png\")
# kubectl get nodes\n<\/pre>\n\n\n\n
![\"Check](\"https:\/\/www.tecmint.com\/wp-content\/uploads\/2020\/01\/Check-Status-of-Master-Nodes.png\")
Adding Worker Nodes to Kubernetes Cluster<\/h3>\n\n\n\n
Step 1: Prepare Hostname, Firewall, and SELinux<\/h4>\n\n\n\n
# hostnamectl set-hostname 'node-1'\n# cat <<EOF>> \/etc\/hosts\n192.168.0.47 master-node\n192.168.0.48 node-1 worker-node-1\n192.168.0.49 node-2 worker-node-2\nEOF\n<\/pre>\n\n\n\n
# 192.168.0.47\n<\/pre>\n\n\n\n
# setenforce 0\n# sed -i --follow-symlinks 's\/SELINUX=enforcing\/SELINUX=disabled\/g' \/etc\/sysconfig\/selinux\n# firewall-cmd --permanent --add-port=6783\/tcp\n# firewall-cmd --permanent --add-port=10250\/tcp\n# firewall-cmd --permanent --add-port=10255\/tcp\n# firewall-cmd --permanent --add-port=30000-32767\/tcp\n# firewall-cmd --reload\n# echo '1' > \/proc\/sys\/net\/bridge\/bridge-nf-call-iptables\n<\/pre>\n\n\n\n
Step 2: Setup Docker-CE and Kubernetes Repo<\/h4>\n\n\n\n
# dnf config-manager --add-repo=https:\/\/download.docker.com\/linux\/centos\/docker-ce.repo\n<\/pre>\n\n\n\n
# dnf install https:\/\/download.docker.com\/linux\/centos\/7\/x86_64\/stable\/Packages\/containerd.io-1.2.6-3.3.el7.x86_64.rpm\n<\/pre>\n\n\n\n
# dnf install docker-ce\n<\/pre>\n\n\n\n
# systemctl enable docker\n# systemctl start docker\n<\/pre>\n\n\n\n
# cat <<EOF > \/etc\/yum.repos.d\/kubernetes.repo\n<\/pre>\n\n\n\n
Step 3: Install Kubeadm on CentOS 8<\/h4>\n\n\n\n
# dnf install kubeadm -y \n<\/pre>\n\n\n\n
# systemctl enable kubelet\n# systemctl start kubelet\n<\/pre>\n\n\n\n
Step 4: Join the Worker Node to the Kubernetes Cluster<\/h4>\n\n\n\n
# kubeadm join 192.168.0.47:6443 --token nu06lu.xrsux0ss0ixtnms5 --discovery-token-ca-cert-hash sha256:f996ea35r4353d342fdea2997a1cf8caeddafd6d4360d606dbc82314683478hjmf78\n<\/pre>\n\n\n\n
# kubectl get nodes\n<\/pre>\n\n\n\n
![\"Check](\"https:\/\/www.tecmint.com\/wp-content\/uploads\/2020\/01\/Check-All-Nodes-Status-in-Kubernetes-Cluster.png\")