Create a cluster
This section guides you in creating of a 3-nodes Kubernetes cluster using kubeadm bootstrapping tool. This is an important step as you will use this cluster throughout this workshop.
The cluster you’ll create is composed of 3 Nodes named controlplane, worker1 and worker2. The controlplane Node runs the cluster components (API Server, Controller Manager, Scheduler, etcd), while worker1 and worker2 are the worker Nodes in charge of running the containerized workloads.
Provisioning VMs 🔗
Before creating a cluster, it’s necessary to provision the infrastructure (bare metal servers or virtual machines). You can create the 3 VMs on your local machine or a cloud provider (but this last option will come with a small cost). Ensure you name those VMs controlplane, worker1, and worker2 to keep consistency alongside the workshop. Please also ensure each VM has at least 2 vCPUs and 2G of RAM so it meets the prerequisites.
If you want to create those VMs on your local machine, we recommend using Multipass, a tool from Canonical. Multipass makes creating local VMs a breeze. Once you have installed Multipass, create the VMs as follows.
multipass launch --name controlplane --memory 2G --cpus 2 --disk 10G
multipass launch --name worker1 --memory 2G --cpus 2 --disk 10G
multipass launch --name worker2 --memory 2G --cpus 2 --disk 10G
Cluster initialization 🔗
Now that the VMs are created, you need to install some dependencies on each on them (a couple of packages including kubectl, containerd and kubeadm). To simplify this process we provide some scripts that will do this job for you.
First, ssh on the controlplane VM and install those dependencies using the following command.
curl https://luc.run/kubeadm/controlplane.sh | VERSION="1.32" sh
Next, still from the controlplane VM, initialize the cluster.
sudo kubeadm init
The initialization should take a few tens of seconds. The list below shows all the steps it takes.
preflight Run pre-flight checks
certs Certificate generation
/ca Generate the self-signed Kubernetes CA to provision identities for other Kubernetes components
/apiserver Generate the certificate for serving the Kubernetes API
/apiserver-kubelet-client Generate the certificate for the API server to connect to kubelet
/front-proxy-ca Generate the self-signed CA to provision identities for front proxy
/front-proxy-client Generate the certificate for the front proxy client
/etcd-ca Generate the self-signed CA to provision identities for etcd
/etcd-server Generate the certificate for serving etcd
/etcd-peer Generate the certificate for etcd nodes to communicate with each other
/etcd-healthcheck-client Generate the certificate for liveness probes to healthcheck etcd
/apiserver-etcd-client Generate the certificate the apiserver uses to access etcd
/sa Generate a private key for signing service account tokens along with its public key
kubeconfig Generate all kubeconfig files necessary to establish the control plane and the admin kubeconfig file
/admin Generate a kubeconfig file for the admin to use and for kubeadm itself
/super-admin Generate a kubeconfig file for the super-admin
/kubelet Generate a kubeconfig file for the kubelet to use *only* for cluster bootstrapping purposes
/controller-manager Generate a kubeconfig file for the controller manager to use
/scheduler Generate a kubeconfig file for the scheduler to use
etcd Generate static Pod manifest file for local etcd
/local Generate the static Pod manifest file for a local, single-node local etcd instance
control-plane Generate all static Pod manifest files necessary to establish the control plane
/apiserver Generates the kube-apiserver static Pod manifest
/controller-manager Generates the kube-controller-manager static Pod manifest
/scheduler Generates the kube-scheduler static Pod manifest
kubelet-start Write kubelet settings and (re)start the kubelet
upload-config Upload the kubeadm and kubelet configuration to a ConfigMap
/kubeadm Upload the kubeadm ClusterConfiguration to a ConfigMap
/kubelet Upload the kubelet component config to a ConfigMap
upload-certs Upload certificates to kubeadm-certs
mark-control-plane Mark a node as a control-plane
bootstrap-token Generates bootstrap tokens used to join a node to a cluster
kubelet-finalize Updates settings relevant to the kubelet after TLS bootstrap
/enable-client-cert-rotation Enable kubelet client certificate rotation
addon Install required addons for passing conformance tests
/coredns Install the CoreDNS addon to a Kubernetes cluster
/kube-proxy Install the kube-proxy addon to a Kubernetes cluster
show-join-command Show the join command for control-plane and worker node
Several commands are returned at the end of the installation process, which you’ll use in the next part.
Retrieving kubeconfig file 🔗
The first set of commands returned during the initialization step allows configuring kubectl for the current user. Run those commands from a shell in the controlplane Node.
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
You can now list the Nodes. You’ll get only one Node as you’ve not added the worker Nodes yet.
$ kubectl get no
NAME STATUS ROLES AGE VERSION
controlplane NotReady control-plane 5m4s v1.32.4
Adding the first worker Node 🔗
As you’ve done for the controlplane, use the following command to install the dependencies (kubectl, containerd, kubeadm) on worker1.
curl https://luc.run/kubeadm/worker.sh | VERSION="1.32" sh
Then, run the join command returned during the initialization step. This command allows you to add worker nodes to the cluster.
sudo kubeadm join 10.81.0.174:6443 --token kolibl.0oieughn4y03zvm7 \
--discovery-token-ca-cert-hash sha256:a1d26efca219428731be6b62e3298a2e5014d829e51185e804f2f614b70d933d
Adding the second worker Node 🔗
You need to do the same on worker2. First, install the dependencies.
curl https://luc.run/kubeadm/worker.sh | VERSION="1.32" sh
Then, run the join command to add this Node to the cluster.
sudo kubeadm join 10.81.0.174:6443 --token kolibl.0oieughn4y03zvm7 \
--discovery-token-ca-cert-hash sha256:a1d26efca219428731be6b62e3298a2e5014d829e51185e804f2f614b70d933d
You now have cluster with 3 Nodes.
Status of the Nodes 🔗
List the Nodes and notice they are all in NotReady status.
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
controlplane NotReady control-plane 9m58s v1.32.4
worker1 NotReady <none> 58s v1.32.4
worker2 NotReady <none> 55s v1.32.4
If you go one step further and describe the controlplane Node, you’ll get why the cluster is not ready yet.
…
KubeletNotReady container runtime network not ready: NetworkReady=false reason:NetworkPluginNotReady message:Network plugin returns error: cni plugin not initialized
Installing a network plugin 🔗
Run the following commands from the controlplane Node to install Cilium in your cluster.
OS="$(uname | tr '[:upper:]' '[:lower:]')"
ARCH="$(uname -m | sed -e 's/x86_64/amd64/' -e 's/\(arm\)\(64\)\?.*/\1\2/' -e 's/aarch64$/arm64/')"
curl -L --remote-name-all https://github.com/cilium/cilium-cli/releases/latest/download/cilium-$OS-$ARCH.tar.gz{,.sha256sum}
sudo tar xzvfC cilium-$OS-$ARCH.tar.gz /usr/local/bin
cilium install
After a few tens of seconds, you’ll see your cluster is ready.
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
controlplane Ready control-plane 13m v1.32.4
worker1 Ready <none> 4m28s v1.32.4
worker2 Ready <none> 4m25s v1.32.4
Get the kubeconfig on the host machine 🔗
To avoid connecting to the controlplane Node to run the kubectl commands, copy the kubeconfig file from the controlplane to the host machine. Make sure to copy this file into $HOME/.kube/config so it automatically configures kubectl.
If you’ve created your VMs with Multipass, you can copy the kubeconfig file using the following commands.
multipass transfer controlplane:/home/ubuntu/.kube/config config
mkdir $HOME/.kube
mv config $HOME/.kube/config
You should now be able to direcly list the Nodes from the host machine.
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
controlplane Ready control-plane 13m v1.32.4
worker1 Ready <none> 4m28s v1.32.4
worker2 Ready <none> 4m25s v1.32.4