Installing Kubernetes on Linux

Installing kubernetes minimally consists of 3 tools.

We'll need to install these tools on all of the nodes: * kubeadm: the command to bootstrap the cluster. * kubelet: the component that runs on all of the machines in your cluster and does things like starting pods and containers. * kubectl: the command line util to talk to your cluster.

The kubeadm tool won't install or manage kubelet/kubectl.
You need to make sure they match the version of the k8s control plane you want kubeadm to install.

The apt.kubernetes.io and yum.kubernetes.io repos are deprecated.
The new repos are at pkgs.k8s.io.

Table of Contents

• Manually Installing K8s Binaries
  • Download/Install kubectl
• K8s install with package managers
  • Install k8s on Rocky/RedHat-based
  • Install k8s on Ubuntu/Debian-based
  • Next Steps for both RedHat and Debian
  • Set up kubeconfig
• Resources

tl;dr

• Disable swap
• Install deps
  • sudo apt install -y apt-transport-https ca-certificates curl gnupg
  • sudo dnf install -y yum-utils device-mapper-persistent-data lvm2
• Add the overlay and br_netfilter kernel modules
  • /etc/modules-load.d/k8s.conf
  • Reload with modprobe br_netfilter and modprobe overlay
• Configure iptables to allow network bridging for both ipv4 and ipv6 as well as ip forwarding
  • /etc/sysctl.d/k8s.conf
  • Reload kernel modules with sysctl --system
• Add apt or dnf repositories
• Install kubelet, kubectl, kubeadm

Manually Installing K8s Binaries

Download/Install kubectl

• Download the binary with curl:

  # x86_64 architecture (amd64):
  curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
  # replace the curl subshell with a specific version if you need:
  curl -LO https://dl.k8s.io/release/v1.32.0/bin/linux/amd64/kubectl
  

  Replace amd64 with arm64 if you need to use ARM64 architecture.

• Optionally validate the binary with checksums:

  curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"
  echo "$(cat kubectl.sha256)  kubectl" | sha256sum --check
  

• Install kubectl with the install command

  sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl
  

  • If you don't have root access:

    chmod 755 kubectl
    mkdir -p ~/.local/bin && mv ./kubectl ~/.local/bin/kubectl
    

• Verify installation:

  kubectl version --client
  kubectl version --client --output=yaml
  

---

K8s install with package managers

Install k8s on Rocky/RedHat-based

docs

# put SELinux into permissive mode if it's active
sudo setenforce 0
sudo sed -i 's/^SELINUX=enforcing$/SELINUX=permissive' /etc/selinux/config

# disable swap (required for k8s)
sudo swapoff -a
sed -i '/swap/d' /etc/fstab  # Permanently disable swap

# make sure deps exist
sudo dnf install -y yum-utils device-mapper-persistent-data lvm2

# Add k8s repository
cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el9-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=0
gpgkey=https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF


# install k8s components
sudo dnf install -y kubelet kubeadm kubectl

# start the kubelet service
sudo systemctl enable --now kubelet

# configure sysctl settings
cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
br_netfilter
EOF

sudo modprobe br_netfilter

cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF

sudo sysctl --system

Install k8s on Ubuntu/Debian-based

docs This is for k8s v1.32.

# disable swap (required for k8s)
sudo swapoff -a
# delete the line in /etc/fstab that contains 'swap'
sed -i '/swap/d' /etc/fstab

# install deps
sudo apt update
sudo apt install -y apt-transport-https ca-certificates curl gnupg

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

# overwrites any existing configuration in /etc/apt/sources.list.d/kubernetes.list
echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.32/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list
sudo chmod 644 /etc/apt/sources.list.d/kubernetes.list   # helps tools such as command-not-found to work correctly

# install k8s components
sudo apt update
sudo apt install -y kubelet kubeadm kubectl

# enable the kubelet service
sudo systemctl enable --now kubelet

# configure sysctl settings (kernel modules)  
# Add a file in /etc/modules-load.d/ that specifies what kernel modules k8s needs 
# the br_netfilter module allows the network bridge traffic to be passed through iptables.
# required by some CNIs (flannel) and others that rely on bridge networking
# also used when working with Kube-proxy
cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
br_netfilter
EOF

# add the `br_netfilter` Linux Kernel Module without needing a reboot
sudo modprobe br_netfilter

# /etc/sysctl.d/ stores config files for persistent kernel settings.  
# This allows bridged ipv4 and ipv6 packets to be processed by iptables.  
# Required for CNIs that rely on Linux bridges. 
cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF

sudo sysctl --system
# This modifies the kernel runtime parameters on the fly, and loads everything in the sysctl.d/*.conf files

Next Steps for both RedHat and Debian

Verify the installtion

kubeadm version
kubelet --version
kubectl version --client

# Generate bash completion script for kubectl 
kubectl completion bash
# enable kubectl autocompletion in .bashrc (requires `bash-completion`)
echo 'source <(kubectl completion bash)' >> ~/.bashrc

# if you have an alias for kubectl, you can extend the compltion to work with the alias
echo 'alias k=kubectl' >> ~/.bashrc
echo 'complete -o default -F __start_kubectl k' >> ~/.bashrc


        # cat <<- 'EOF' >> ~/.bashrc
            # source <(kubectl completion bash)
            # alias k=kubectl
            # complete -o default -F __start_kubectl k
        # EOF

• Initialize the cluster (done later).

Set up kubeconfig

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

Resources

• Installing kubeadm
• Installing kubectl