Create a Debian 11 kubernetes cluster with kubeadm

In this blog, I’ll try to keep as simple as possible to get up and running a Kubernetes cluster.
The cluster will be composed of three machines, one control plane and two workers.
I used KVM (Kernel-based Virtual Machine) running Debian 11 and installed a minimal system with SSH.
Note: this tutorial is made for learning, doesn’t cover any security or best practices.



The following setup has to be done on all three machines to be more efficient you can use a terminal multiplexer like tmux.

Edit hosts file with your favorite editor and add the following lines with your right IP addresses.

sudo vim /etc/hosts c1-control-plane c1-worker-1 c1-worker-2

Load required modules and set kernel settings.
overlay it’s needed for overlayfs,
br_netfilter for iptables to correctly see bridged traffic,

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

cat << EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
net.ipv4.ip_forward = 1
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1

Turn off swap, as kubelet requires that

sudo sed -i '/swap/d' /etc/fstab

Apply settings, you can also skip this by rebooting the machines.

sudo modprobe overlay
sudo modprobe br_netfilter
sudo sysctl --system
sudo swapoff -a

Install an NTP server otherwise etcd will be mad.

sudo apt install -y chrony

Install containerd

# requirements

sudo apt install -y curl gpg lsb-release apparmor apparmor-utils
curl -fsSL | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
echo "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

# install

sudo apt update
sudo apt-get install -y
sudo mkdir -p /etc/containerd
sudo containerd config default | sudo tee /etc/containerd/config.toml

Edit containerd configuration and restart service

sudo vim /etc/containerd/config.toml
            SystemdCgroup = true


  SystemdCgroup = true
sudo systemctl restart containerd

Install kubernetes tools, in my case version 1.21.0.

# requirements

sudo apt-get install -y apt-transport-https ca-certificates curl
sudo curl -fsSLo /usr/share/keyrings/kubernetes-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/kubernetes-archive-keyring.gpg] kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list

# install

sudo apt-get update
sudo apt install iptables libiptc0/stable libxtables12/stable
sudo apt-get install -y kubelet=1.21.0-00 kubeadm=1.21.0-00 kubectl=1.21.0-00
sudo apt-mark hold kubelet kubeadm kubectl

Now it's time to create our Kubernetes cluster the following commands needs to be run from the control plane only.

sudo kubeadm init --pod-network-cidr --kubernetes-version 1.21.0
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

From the control plane node you can now check you kubernetes cluster, c1-control-plane is in not NotReady mode because we didn't set up the networking yet.

kubectl get nodes
NAME               STATUS     ROLES                  AGE     VERSION
c1-control-plane   NotReady   control-plane,master   3m49s   v1.21.0

Setup networking with calico

kubectl apply -f

Join the other nodes to our cluster, the command must be run on the worker nodes only.
At the end of the "kubeadmin init ..." command you were prompted for a join command, it should look like:

sudo kubeadm join --token oxaul0.24g50wlwsp4ktiqs --discovery-token-ca-cert-hash sha256:74746c748be5fef131d9c91a591c053591b6ce1e274396bcb7c48b6e6664bded

If you missed it, you can still generate a token and generate the command with:

kubeadm token create --print-join-command

We are ready, the setup can be validate with kubectl, all nodes are in ready state and kube-system pods are running.

kubectl get nodes
NAME               STATUS   ROLES                  AGE     VERSION
c1-control-plane   Ready    control-plane,master   5m52s   v1.21.0
c1-worker-1        Ready                     2m10s   v1.21.0
c1-worker-2        Ready                     66s     v1.21.0
kubectl get pods -A
kube-system   calico-kube-controllers-78d6f96c7b-9q4lq   1/1     Running   0          9h
kube-system   calico-node-4mq7p                          1/1     Running   0          9h
kube-system   calico-node-8km7w                          1/1     Running   0          9h
kube-system   calico-node-sjzs4                          1/1     Running   0          9h
kube-system   coredns-558bd4d5db-7pbjx                   1/1     Running   0          9h
kube-system   coredns-558bd4d5db-ptn59                   1/1     Running   0          9h
kube-system   etcd-c1-control-plane                      1/1     Running   1          9h
kube-system   kube-apiserver-c1-control-plane            1/1     Running   0          9h
kube-system   kube-controller-manager-c1-control-plane   1/1     Running   0          9h
kube-system   kube-proxy-ls768                           1/1     Running   0          9h
kube-system   kube-proxy-mk98k                           1/1     Running   0          9h
kube-system   kube-proxy-qbxwb                           1/1     Running   0          9h
kube-system   kube-scheduler-c1-control-plane            1/1     Running   0          9h

11 Replies to “Create a Debian 11 kubernetes cluster with kubeadm”

  1. This is the best walkthrough I’ve found so far. The only thing I had to change was around swap. On my debian 11, there must be some systemd process turning on swap after a reboot, even with /etc/fstab swap disabled.

    I had to delete the swap partition, add a new non-swap version (fdisk /dev/sda). Then, to be sure I ran mkfs the /dev/sda3 partition.

    I did some digging through systemd for swap references, but no luck yet.

    Great job!

    1. Thank you for the feedback, indeed I had recently such issue and managed to workaround so far only by removing the swap partition, can be done with fdisk or parted.

  2. Hello, With Debian 10, I had no issues deploying Kubernetes however with 11 the connection with the API keeps being lost, have you experienced something like that?

    1. I have spent all day troubleshooting this exact same problem!! Driving me mad as I’m a k8s newbie and couldn’t find any reference on the web to the API connection being lost every so often. I cracked it though:

      On a rare occasion where I could use kubectl, I checked the various control plane pod logs and found they kept restarting since they couldn’t connect to the api using the hostname. I didn’t put two and two together at the time but it’s because in /etc/hosts the hostname is set to the loopback IP ( I would assume this doesn’t work as the API only listens on the main network interface. I never bothered changing the hosts file since I figured I’d do it all in one go once I’d created the worker nodes, but following this tutorial and editing the hostname IP to the nodes priv address fixed all my problems.

      If anyone

  3. Hello Alxndr3,

    Not really on my side the Debian 11 deployment it’s fine, you should check the kube-api pod logs.

    Thanks for your feedback

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