k8s

1. standard

• 2GB or more of RAM
• 2CPUs or more

2. prepare

• You need to install a container runtime into each node in the cluster

• Certain ports are open on your machines

  • systemctl firewalld stop

• Disable swap

  • swapoff -a
  • check /etc/fstab

• Verify glibc is provide or not in machines

• Verify the MAC address and product_uuid are unique for every node

  • ip link
  • ifconfig -a
  • cat /sys/class/dmi/id/product_uuid

• Check required ports

  • nc 127.0.0.1 6443

3. Installing kubeadm, kubelet and kubectl

kubelet version may never exceed the API server version.

For example, the kubelet running 1.7.0 should be fully compatible with a 1.8.0 API server, but not vice versa.

Red Hat-based distributions

• Set SELinux to permissive mode

  • setenforce 0
  • sed -i ‘s/^SELINUX=enforcing$/SELINUX=permissive/’ /etc/selinux/config

• Add the Kubernetes yum repository

  cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
  [kubernetes]
  name=Kubernetes
  baseurl=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/
  enabled=1
  gpgcheck=1
  gpgkey=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/repodata/repomd.xml.key
  exclude=kubelet kubeadm kubectl cri-tools kubernetes-cni
  EOF
  

• Install kubelet, kubeadm and kubectl, and enable kubelet to ensure it’s automatically started on startup

  • yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
  • systemctl enable --now kubelet

Without a package manager

• Install CNI plugins (required for most pod network)

  CNI_PLUGINS_VERSION="v1.3.0"
  ARCH="amd64"
  DEST="/opt/cni/bin"
  sudo mkdir -p "$DEST"
  curl -L "https://github.com/containernetworking/plugins/releases/download/${CNI_PLUGINS_VERSION}/cni-plugins-linux-${ARCH}-${CNI_PLUGINS_VERSION}.tgz" | sudo tar -C "$DEST" -xz
  

• Define the directory to download command files

  DOWNLOAD_DIR="/usr/local/bin"
  sudo mkdir -p "$DOWNLOAD_DIR"
  

• Install crictl (required for kubeadm / Kubelet Container Runtime Interface (CRI))

  CRICTL_VERSION="v1.28.0"
  ARCH="amd64"
  curl -L "https://github.com/kubernetes-sigs/cri-tools/releases/download/${CRICTL_VERSION}/crictl-${CRICTL_VERSION}-linux-${ARCH}.tar.gz" | sudo tar -C $DOWNLOAD_DIR -xz
  

• Install kubeadm, kubelet, kubectl and add a kubelet systemd service

  RELEASE="$(curl -sSL https://dl.k8s.io/release/stable.txt)"
  ARCH="amd64"
  cd $DOWNLOAD_DIR
  sudo curl -L --remote-name-all https://dl.k8s.io/release/${RELEASE}/bin/linux/${ARCH}/{kubeadm,kubelet}
  sudo chmod +x {kubeadm,kubelet}
  
  RELEASE_VERSION="v0.16.2"
  curl -sSL "https://raw.githubusercontent.com/kubernetes/release/${RELEASE_VERSION}/cmd/krel/templates/latest/kubelet/kubelet.service" | sed "s:/usr/bin:${DOWNLOAD_DIR}:g" | sudo tee /etc/systemd/system/kubelet.service
  sudo mkdir -p /etc/systemd/system/kubelet.service.d
  curl -sSL "https://raw.githubusercontent.com/kubernetes/release/${RELEASE_VERSION}/cmd/krel/templates/latest/kubeadm/10-kubeadm.conf" | sed "s:/usr/bin:${DOWNLOAD_DIR}:g" | sudo tee /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
  

  Notes:

  Site raw.githubusercontent.com is 404 … replace following url

  https://github.com/kubernetes/release/blob/master/cmd/krel/templates/latest/kubelet/kubelet.service

  https://github.com/kubernetes/release/blob/master/cmd/krel/templates/latest/kubeadm/10-kubeadm.conf

  cat >> /etc/systemd/system/kubelet.service << 'EOF'
  [Unit]
  Description=kubelet: The Kubernetes Node Agent
  Documentation=https://kubernetes.io/docs/
  Wants=network-online.target
  After=network-online.target
  
  [Service]
  ExecStart=/usr/bin/kubelet
  Restart=always
  StartLimitInterval=0
  RestartSec=10
  
  [Install]
  WantedBy=multi-user.target
  EOF
  cat >> /etc/systemd/system/kubelet.service.d/10-kubeadm.conf << 'EOF'
  # Note: This dropin only works with kubeadm and kubelet v1.11+
  [Service]
  Environment="KUBELET_KUBECONFIG_ARGS=--bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf"
  Environment="KUBELET_CONFIG_ARGS=--config=/var/lib/kubelet/config.yaml"
  # This is a file that "kubeadm init" and "kubeadm join" generates at runtime, populating the KUBELET_KUBEADM_ARGS variable dynamically
  EnvironmentFile=-/var/lib/kubelet/kubeadm-flags.env
  # This is a file that the user can use for overrides of the kubelet args as a last resort. Preferably, the user should use
  # the .NodeRegistration.KubeletExtraArgs object in the configuration files instead. KUBELET_EXTRA_ARGS should be sourced from this file.
  EnvironmentFile=-/etc/sysconfig/kubelet
  ExecStart=
  ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS
  EOF
  

• Install and Set Up kubectl on Linux

  • Install kubectl binary with curl on Linux

    1. Download the latest release with the command

       curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
       
       ## View stable version
       curl -L -s https://dl.k8s.io/release/stable.txt
       

    2. Validate the binary (optional)

       ## Download the kubectl checksum file
       curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"
       
       ## Validate the kubectl binary against the checksum file
       echo "$(cat kubectl.sha256)  kubectl" | sha256sum --check
       

    3. Install kubectl

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

    4. Test to ensure the version you installed is up-to-date

       kubectl version --client
       ## Or use this for detailed view of version
       kubectl version --client --output=yaml
       

  • Install using native package management

    1. Add the Kubernetes yum repository. If you want to use Kubernetes version different than v1.29, replace v1.29 with the desired minor version in the command below.

       # This overwrites any existing configuration in /etc/yum.repos.d/kubernetes.repo
       cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
       [kubernetes]
       name=Kubernetes
       baseurl=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/
       enabled=1
       gpgcheck=1
       gpgkey=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/repodata/repomd.xml.key
       EOF
       

    2. Install kubectl using yum

       sudo yum install -y kubectl
       

• Enable and start kubelet

  • systemctl enable --now kubelet
    

Container runtimes

kubeadm init output error

[ERROR CRI]: container runtime is not running

https://github.com/containerd/containerd/blob/main/docs/getting-started.md

https://github.com/containerd/containerd/blob/main/containerd.service

yum -y install socat conntrack-tools