Setup Kubernetes Cluster Using Kubeadm

Kubeadm Setup Prerequisites

Following are the prerequisites for Kubeadm Kubernetes cluster setup.

1. Minimum two Ubuntu nodes [One master and one worker node]. You can have more worker nodes as per your requirement.
2. The master node should have a minimum of 2 vCPU and 2GB RAM.
3. For the worker nodes, a minimum of 1vCPU and 2 GB RAM is recommended.
4. 10.X.X.X/X network range with static IPs for master and worker nodes. We will be using the 192.x.x.x series as the pod network range that will be used by the Calico network plugin. Make sure the Node IP range and pod IP range don't overlap.

On cp1:

sudo hostnamectl set-hostname cp1

On worker1:

sudo hostnamectl set-hostname w1

On worker2:

sudo hostnamectl set-hostname w2

Add entries to /etc/hosts on all nodes:

sudo nano /etc/hosts

Add the following to the end of the file, replacing with your IP addresses:

10.0.0.10   cp1
10.0.0.11   w1
10.0.0.12   w2

This allows nodes to address each other by name rather than by IP address.

1. General system preparation (all nodes)

1.1. Updating packages

sudo apt update
sudo apt upgrade -y

We are simply updating the system to avoid bugs caused by old packages.

1.2. Disable swap (required for kubeadm)

On all nodes:

sudo swapoff -a
sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

Verification:

free -h

1.3. Kernel modules and sysctl (for the grid)↵↵On each node:

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

Now sysctl:

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

This includes correct traffic handling through the Linux bridge and forwarding — mandatory for CNI (Calico).

1.4. (For lab) Disable UFW

If UFW is enabled and this is a clean lab:

sudo ufw disable

In Prod, of course, it is better to open the necessary ports, but for the first build it is easier without a firewall.

2. Install containerd (all nodes)

At each node:

sudo apt install -y containerd

Generate default configuration:

sudo mkdir -p /etc/containerd
sudo containerd config default | sudo tee /etc/containerd/config.toml > /dev/null

Restart and switch on:

sudo systemctl restart containerd
sudo systemctl enable containerd
sudo systemctl status containerd

SystemdCgroup = true → kubelet and containerd use the same cgroup driver (systemd). This is now considered best practice.

3. Install kubeadm/kubelet/kubectl 1.34 (all nodes)

According to the official documentation for v1.34:

3.1. Repo packages

At each node:

sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates curl gpg

3.2. GPG key and pkgs.k8s.io repository (v1.34)↵↵Ubuntu 22.04 already has /etc/apt/keyrings, but if it doesn't:

sudo mkdir -p -m 755 /etc/apt/keyrings

Repository key:

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.34/deb/Release.key \

 | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

Add repo specifically for Kubernetes 1.34:

echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.34/deb/ /" \

 | sudo tee /etc/apt/sources.list.d/kubernetes.list

3.3. Installing kubeadm/kubelet/kubectl

sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl

Repository v1.34 ensures that branch 1.34.x is installed. apt-mark hold will prevent accidental updates to other minor versions during apt upgrade.

(Not required, but you can enable kubelet immediately; it will run and wait for kubeadm init / join):

sudo systemctl enable --now kubelet

5. Control-plane initialisation (cp1 only)

Now we create a cluster on cp1.

5.1. kubeadm init with pod-CIDR for Calico

Calico uses 192.168.0.0/16 by default. For convenience, we will use the same:

On cp1:

sudo kubeadm init \
  --apiserver-advertise-address=10.0.0.10 \
  --pod-network-cidr=192.168.0.0/16

• --apiserver-advertise-address — IP cp1, which everyone will use to access the API.
• --pod-network-cidr — The IP range for pods that Calico will use.

At the end, kubeadm will output:

• message about successful initialisation;
• The command kubeadm join ... — be sure to copy it somewhere (we will use it on the workers).

5.2. Configuring kubectl for the sadmin user (cp1)

Currently, kubeconfig is located in /etc/kubernetes/admin.conf and belongs to root.

On cp1 under sadmin:

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

Verification:

kubectl get nodes

Until the network is up, the node may be NotReady — this is normal.

6. Install Calico 3.31 (cp1 only)

We take the latest Calico 3.31.1 from the official on-prem instructions.

6.1. Tigera Operator + CRD

On cp1:

kubectl create -f https://raw.githubusercontent.com/projectcalico/calico/v3.31.1/manifests/operator-crds.yaml
kubectl create -f https://raw.githubusercontent.com/projectcalico/calico/v3.31.1/manifests/tigera-operator.yaml

This sets the Calico operator, which then rolls out the necessary components across the nodes itself.

6.2. Calico configuration (custom-resources)

By default, we use iptables-dataplane (without eBPF, so as not to complicate things for now).

On cp1:

curl -O https://raw.githubusercontent.com/projectcalico/calico/v3.31.1/manifests/custom-resources.yaml
kubectl create -f custom-resources.yaml

(If you want eBPF in the future, there is also custom-resources-bpf.yaml.)

6.3. Verify that Calico has started

On cp1:

watch kubectl get tigerastatus

We are waiting until everything is AVAILABLE=True:

NAME              AVAILABLE   PROGRESSING   DEGRADED   SINCE
calico            True        False         False      ...
ippools           True        False         False      ...
...

And let's look at the pods:

kubectl get pods -n calico-system
kubectl get pods -n kube-system
kubectl get nodes

cp1 should transition to Ready status.

7. Make the control plane "clean" (without workload pods)

By default, in 1.34, the control plane can accept normal pods (taint is not set automatically).

You don't need this, so let's set taint right away:

On cp1:

kubectl taint nodes cp1 node-role.kubernetes.io/control-plane=:NoSchedule

Verification:

kubectl describe node cp1 | grep -i Taint

It should be something like:

Taints: node-role.kubernetes.io/control-plane:NoSchedule

Now the scheduler will NOT place regular pods on cp1. Only system components will remain there (kube-apiserver, etcd, kube-controller-manager, scheduler, Calico DaemonSet, etc.).

8. Connect worker1 and worker2

8.1. Obtain the join command (if lost)

If you did not save the output of kubeadm init, on cp1:

sudo kubeadm token create --print-join-command

Example:

kubeadm join 10.0.0.10:6443 --token abcdef.0123456789abcdef \

 --discovery-token-ca-cert-hash sha256:xxxxxxxx...

8.2. Perform a join on worker1 / worker2↵↵On worker1:

sudo kubeadm join 10.0.0.10:6443 --token abcdef.0123456789abcdef \

 --discovery-token-ca-cert-hash sha256:xxxxxxxx...

On worker2:

sudo kubeadm join 10.0.0.10:6443 --token abcdef.0123456789abcdef \

 --discovery-token-ca-cert-hash sha256:xxxxxxxx...

Here, a token and CA hash are used to enable workers to securely join the cluster.

After that, on cp1:

kubectl get nodes

Expected result:

NAME      STATUS   ROLES           AGE   VERSION
cp1       Ready    control-plane   20m   v1.34.x
worker1   Ready    <none>          5m    v1.34.x
worker2   Ready    <none>          3m    v1.34.x

If workers are NotReady for some time, wait until kube-proxy + Calico catch up and start.

9. Verification: only on worker nodes

Let's create a test deployment:

On cp1:

kubectl create deployment nginx --image=nginx --replicas=3
kubectl expose deployment nginx --port=80 --type=NodePort

Let's see:

kubectl get pods -o wide

Все pod’ы nginx должны сидеть на worker1 и worker2, но не на cp1. Если вдруг увидишь под на cp1, значит taint не применился → ещё раз:

kubectl taint nodes cp1 node-role.kubernetes.io/control-plane=:NoSchedule --overwrite
kubectl rollout restart deploy nginx

✅ 1. Как удалить эти pod’ы (Deployment + Service)

Ты создал:

• Deployment: nginx
• Service: nginx

Чтобы удалить:

kubectl delete service nginx

Удалить Deployment:

kubectl delete deployment nginx

Проверяем:

kubectl get pods
kubectl get svc

📌 Если хочешь удалить ВСЁ, что относится к nginx, одной командой:

kubectl delete deploy,svc nginx