Setting up control plane node
To init the control plane node with kubeadm simply ssh on the node and run the following command:
sudo kubeadm init
Wait for it to finish.
What does kubeadm init do?
The kubeadm init command does a lot of things:
- Install the necessary packages on the system
- Create a Kubernetes configuration file
- Create static pods for the control plane components
- Generate certificates and keys for the cluster
- Generate a kubeconfig for the control plane components
- Generate a token to be used by the worker nodes to join the cluster
- Generate a kubeconfig for the admin user
Setup kubeconfig
To be able to use kubectl we need to setup the kubeconfig file.
This configuration file is created by kubeadm and is located at /etc/kubernetes/admin.conf.
This enables us to interact with our Kubernetes cluster, currently with only one node as the admin user.
Run the following commands to copy the configuration file to the default location and change the ownership of the file to the current user:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Check that control plane is up
We now have a control plane node up and running. To check that everything is working, you can run the following command:
kubectl get nodes
You should see something like this:
NAME STATUS ROLES AGE VERSION
controlplane NotReady control-plane 10m v1.25.0
The control plane node should be in the NotReady state yet. This is normal, we will fix this in the next section.
Install CNI plugin
The control plane node is not ready because the pods are not able to communicate with each other.
If you run the following command:
kubectl get pods --all-namespaces
You will see something like this:
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-74ff55c5b-2q2q2 0/1 Pending 0 10m
kube-system coredns-74ff55c5b-4q4q4 0/1 Pending 0 10m
kube-system etcd-controlplane 1/1 Running 0 10m
kube-system kube-apiserver-controlplane 1/1 Running 0 10m
kube-system kube-controller-manager-controlplane 1/1 Running 0 10m
kube-system kube-proxy-2q2q2 1/1 Running 0 10m
kube-system kube-scheduler-controlplane 1/1 Running 0 10m
You can see that the coredns pods are not ready and are in the Pending state. This is because the pods are waiting for a network to be available.
To fix this, we need to install a Container Network Interface (CNI) plugin. A CNI plugin is a network plugin that will allow pods to communicate with each other.
We will use Weave Net in this course.
kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.30.2/manifests/calico.yaml
Wait for the weave-net pods to be ready:
kubectl -n kube-system wait pod -l k8s-app=calico-kube-controllers --for=condition=Ready --timeout=-1s
kubectl get pods -l k8s-app=calico-kube-controllers -n kube-system
Check that control plane node is ready
To check that everything is working you can run the following command:
kubectl get nodes
You should see something like this:
NAME STATUS ROLES AGE VERSION
controlplane Ready master 10m v1.25.0
The control plane node should be in the Ready state now.
We can also check that the coredns pod is now running:
kubectl get pods --all-namespaces
You should see something like this:
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-74ff55c5b-2q2q2 1/1 Running 0 10m
kube-system etcd-controlplane 1/1 Running 0 10m
kube-system kube-apiserver-controlplane 1/1 Running 0 10m
kube-system kube-controller-manager-controlplane 1/1 Running 0 10m
kube-system kube-proxy-2q2q2 1/1 Running 0 10m
kube-system kube-scheduler-controlplane 1/1 Running 0 10m
Join worker nodes
In the next section, we will make our worker nodes join the cluster.