my-docs/kubernetes/info.md

Kubernetes (Kuber) Documentation

Control Plane (CP)

• CP (Control Plane): The central management entity of the Kubernetes cluster.
• By default, the manager in Kubernetes does not directly handle any containers.

Kubernetes Manager Components

• Control Manager
• Scheduler
• API Server
• etcd (Database)
• Kubelet

Kubernetes Worker Components

• Kube Proxy
• Kubelet

Data Flow

• Kube Proxy and Kubelet communicate with the Kubernetes Manager for data handling.

Administration Tools

• kubeadm: Used for administration commands.
• kubectl: Used to manage nodes and services.

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Kubernetes Setup

Step 1: Write Default Config

1. Generate the default containerd configuration.

   containerd config default > /etc/containerd/config.toml
   

Step 2: Modify Config

1. Change systemd_cgroup to true.

   vim /etc/containerd/config.toml
   

2. Restart the containerd service.

   systemctl restart containerd
   

Step 3: Load Required Modules

1. Load necessary kernel modules.

   modprobe br_netfilter overlay
   lsmod | grep overlay  # To verify the overlay module is loaded
   

2. Add the modules to load at boot.

   vim /etc/modules-load.d/modules.conf
   

   Add the following lines:

   br_netfilter
   overlay
   

Step 4: Enable IPv4 Forwarding

1. Update Config File

    sed -i 's/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/' /etc/sysctl.conf && sysctl -p
   

Step 5: Install Required Packages

1. Install necessary packages.

   sudo apt install ca-certificates curl apt-transport-https conntrack -y
   

Step 6: Install Kubernetes Components

1. Add Kubernetes keyring.

   curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.30/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
   

2. Add Kubernetes to the sources list.

   echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.30/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list
   

3. Update package list and install Kubernetes components.

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

4. Hold the package versions.

   sudo apt-mark hold kubelet kubeadm kubectl
   

5. Enable and start kubelet.

   sudo systemctl enable --now kubelet
   

Step 7: Setup Network Protocol

1. Initialize the Kubernetes cluster.

   kubeadm init --apiserver-advertise-address <ip-interface> --pod-network-cidr 10.244.0.0/16
   

2. Apply the Flannel CNI plugin for network management.

   kubectl apply -f https://github.com/flannel-io/flannel/releases/latest/download/kube-flannel.yml
   

3. Configure kubectl for the current user.

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

Step 8: Generate Join Command

1. Generate the command to join worker nodes to the cluster.

   kubeadm token create --print-join-command
   

This command will print out a token and the complete command to be used on worker nodes to join them to the cluster.