Lesson 8: Installing Kubernetes Tools (kubectl, kubeadm, kubelet)

In this lesson, you will learn how to install and configure essential Kubernetes tools on your Raspberry Pi devices to prepare them for cluster initialization.

This is the 8th lesson of the guide Building a production-ready Kubernetes cluster from scratch. Make sure you have completed the previous lesson before continuing here. The full list of lessons in the guide can be found in the overview.

In this lesson, we will install the essential Kubernetes tools required to set up and manage your cluster: kubectl, kubeadm, and kubelet. These tools will allow you to initialize the control plane, manage nodes, and control your cluster.

Update the System

Before installing the Kubernetes tools, ensure your Raspberry Pi devices are up to date by running the following commands:

# Update the package list
$ apt update
# Upgrade the installed packages
$ apt upgrade

Installing Kubernetes Tools on Each Raspberry Pi

The Kubernetes tools are essential for managing your cluster and interacting with the Kubernetes API. To install these tools on your Raspberry Pi devices, follow these steps (or the documentation):

1. Install dependencies required for the Kubernetes apt repository:

   $ apt install -y apt-transport-https ca-certificates curl gnupg
   

2. Download the public signing key for the Kubernetes package repositories. The same signing key is used for all repositories so you can disregard the version in the URL:

   $ mkdir -p -m 755 /etc/apt/keyrings
   $ curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.32/deb/Release.key | gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
   
   # allow unprivileged APT programs to read this keyring
   $ chmod 644 /etc/apt/keyrings/kubernetes-apt-keyring.gpg
   

3. Add the appropriate Kubernetes apt repository. We will install version 1.31, which is not the latest version at the time of this writing, allow us to upgrade it later on:

   $ echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.31/deb/ /' >> /etc/apt/sources.list.d/kubernetes.list
   $ chmod 644 /etc/apt/sources.list.d/kubernetes.list
   

4. Update apt package index, then install kubeadm, kubectl, and kubelet:

   $ apt update
   Hit:1 http://deb.debian.org/debian bookworm InRelease
   Hit:2 http://deb.debian.org/debian-security bookworm-security InRelease
   Hit:3 http://deb.debian.org/debian bookworm-updates InRelease
   Hit:4 http://archive.raspberrypi.com/debian bookworm InRelease
   Get:5 https://prod-cdn.packages.k8s.io/repositories/isv:/kubernetes:/core:/stable:/v1.31/deb  InRelease [1,186 B]
   Get:6 https://prod-cdn.packages.k8s.io/repositories/isv:/kubernetes:/core:/stable:/v1.31/deb  Packages [9,749 B]
   Fetched 10.9 kB in 1s (21.1 kB/s)
   Reading package lists... Done
   Building dependency tree... Done
   Reading state information... Done
   All packages are up to date.
   
   $ apt install -y kubelet kubeadm kubectl
   Reading package lists... Done
   Building dependency tree... Done
   Reading state information... Done
   The following additional packages will be installed:
     conntrack cri-tools kubernetes-cni
   The following NEW packages will be installed:
     conntrack cri-tools kubeadm kubectl kubelet kubernetes-cni
   ...
   

5. Holding these packages ensures they will not be automatically updated, which helps maintain cluster stability.

   $ apt-mark hold kubelet kubeadm kubectl
   kubelet set on hold.
   kubeadm set on hold.
   kubectl set on hold.
   

Verifying the Installation

To confirm that the Kubernetes tools have been successfully installed:

• Check the versions of the installed tools by running:

  $ kubectl version --client
  Client Version: v1.31.6
  Kustomize Version: v5.4.2
  $ kubeadm version
  kubeadm version: &version.Info{Major:"1", Minor:"31", GitVersion:"v1.31.6", GitCommit:"6b3560758b37680cb713dfc71da03c04cadd657c", GitTreeState:"clean", BuildDate:"2025-02-12T21:31:09Z", GoVersion:"go1.22.12", Compiler:"gc", Platform:"linux/arm64"}
  $ kubelet --version
  Kubernetes v1.31.6
  

  Ensure that each command returns a version number, indicating the tools are correctly installed.

Configuring Kubernetes Tools

Ensure that kubelet is enabled to start on boot and is running:

$ systemctl enable kubelet
$ systemctl start kubelet

We can see the status of the service by using systemctl and journalctl:

$ systemctl status kubelet
● kubelet.service - kubelet: The Kubernetes Node Agent
     Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; preset: enabled)
    Drop-In: /usr/lib/systemd/system/kubelet.service.d
             └─10-kubeadm.conf
     Active: activating (auto-restart) (Result: exit-code) since Fri 2025-01-17 16:19:50 CET; 5s ago
       Docs: https://kubernetes.io/docs/
    Process: 18044 ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS (code=exited, status=1/FAILURE)
   Main PID: 18044 (code=exited, status=1/FAILURE)
        CPU: 66ms

$ journalctl -u kubelet.service
Jan 17 16:14:53 kubernetes-node-1 systemd[1]: Started kubelet.service - kubelet: The Kubernetes Node Agent.
Jan 17 16:14:53 kubernetes-node-1 kubelet[17651]: E0117 16:14:53.701110   17651 run.go:72] "command failed" err="failed to load kubelet config file, path: /var/lib/kubelet/config.yaml, error: failed to load Kubelet config file /var/lib/kubelet/config.yaml, error failed to read kubelet config file \"/var/lib/kubelet/config.yaml\", error: open /var/lib/kubelet/co>
Jan 17 16:14:53 kubernetes-node-1 systemd[1]: kubelet.service: Main process exited, code=exited, status=1/FAILURE
Jan 17 16:14:53 kubernetes-node-1 systemd[1]: kubelet.service: Failed with result 'exit-code'.

As you can see the service is not running correctly, because we have not yet set up a Kubernetes cluster. We will do that in an upcoming lesson and you can safely ignore the errors for now.

Installing k9s (Optional)

k9s offers a terminal-based UI for interacting with your Kubernetes clusters and is available for free on GitHub. This tool simplifies the navigation, observation, and management of your applications in the terminal. It continuously monitors Kubernetes for changes and provides commands to interact with the observed resources.

To install k9s on your Raspberry Pi devices, we will add the k9s Debian repository to your system:

$ wget https://github.com/derailed/k9s/releases/download/v0.32.7/k9s_linux_arm64.deb -O /tmp/k9s_linux_arm64.deb

Install the k9s package: Install the k9s package:

$ dpkg -i /tmp/k9s_linux_arm64.deb

Selecting previously unselected package k9s.
(Reading database ... 78776 files and directories currently installed.)
Preparing to unpack /tmp/k9s_linux_arm64.deb ...
Unpacking k9s (0.32.7) ...
Setting up k9s (0.32.7) ...

Run k9s to verify the installation:

$ k9s version

 ____  __.________
|    |/ _/   __   \______
|      < \____    /  ___/
|    |  \   /    /\___ \
|____|__ \ /____//____  >
        \/            \/

Version:    v0.32.7
Commit:     6b5d24f5741a1789fb97ba3e11f0ee868d93459d
Date:       2024-11-16T20:22:28Z
root@kubernetes-node-2:~#

Lesson Conclusion

Congratulations! With the Kubernetes tools installed and configured, your Raspberry Pi devices are now ready to initialize the cluster You have completed this lesson and you can now continue with the next one.