How to Run Kubernetes Cluster inside Docker Container

How to Run Kubernetes inside Docker Container using Rancher

What is Rancher

Rancher is a powerful open-source platform for managing Kubernetes clusters. Installing Rancher on a single node is an efficient way to evaluate its capabilities or manage a small-scale deployment. In this guide, we will walk through the steps to set up Rancher using Docker on a single-node setup, leveraging Docker Compose for simplicity.

Prerequisites

Before we begin, ensure you meet the following prerequisites:

1. Operating System: A Linux-based system (e.g., Ubuntu or Debian) with Docker installed.
2. Docker: Installed and running. Use the command docker --version to verify.
3. Sufficient Resources: At least 4 GB of RAM and 2 CPU cores are recommended for running Rancher.

Step 1: Create a Docker Compose File

The following Docker Compose file will set up Rancher in a single-node configuration. Save the file as docker-compose.yml in a directory of your choice:

version: '3.8'

services:
  rancher:
    image: rancher/rancher:latest  # Use the latest Rancher image from Docker Hub
    container_name: rancher        # Assign a custom container name
    restart: unless-stopped        # Automatically restart the container unless stopped manually
    privileged: true               # Required for Rancher to manage Kubernetes clusters
    ports:
      - "800:80"                  # Map HTTP traffic on port 80 to the host's port 800
      - "4430:443"                # Map HTTPS traffic on port 443 to the host's port 4430
    volumes:
      - /opt/rancher:/var/lib/rancher # Persist Rancher data to the host to retain state

Explanation of Key Settings

1. image: Specifies the Rancher Docker image.
2. privileged: Allows Rancher to perform administrative tasks on the host system.
3. ports: Maps container ports to the host system. You can adjust these as needed.
4. volumes: Ensures Rancher data is persisted between container restarts.

Step 2: Deploy Rancher

Navigate to the directory containing your docker-compose.yml file and run the following command:

docker-compose up -d

This command starts Rancher in detached mode.

Step 3: Verify the Installation

Run the following command to check the status of your Rancher container:

docker ps

You should see the rancher container running. If you encounter any issues, check the logs with:

docker logs rancher

Step 4: Access Rancher

Open a web browser and navigate to https://<your-host-ip>:4430.

Replace <your-host-ip> with your server’s IP address. Follow the on-screen instructions to set up an admin account and complete the initial configuration.

Step 5: Configure Kubernetes

Once Rancher is up and running, you can start adding or creating Kubernetes clusters. Rancher simplifies this process with an intuitive user interface and robust automation tools.

Configuring Kubectl to Use a Rancher-Managed Kubernetes Cluster

After installing Kubectl, configure it to interact with a Kubernetes cluster managed by Rancher. Follow these steps:

Step 1: Download the KubeConfig File

Log in to the Rancher UI and download the kubeconfig.yaml file for your cluster. This file contains the necessary credentials and cluster information for Kubectl.

Step 2: Place the KubeConfig File in the Default Directory

Move the downloaded kubeconfig.yaml file to the Kubernetes configuration directory:

mkdir -p ~/.kube
mv kubeconfig.yaml ~/.kube/config

Step 3: Set the KUBECONFIG Environment Variable

Export the KUBECONFIG environment variable to point to your configuration file:

export KUBECONFIG=/home/user/.kube/config/kubeconfig.yaml

Replace /home/user with your actual home directory path.

Step 4: Make the Configuration Persistent

Add the export line to your ~/.bashrc file to ensure it persists across sessions:

echo 'export KUBECONFIG=/home/user/.kube/config/kubeconfig.yaml' >> ~/.bashrc
source ~/.bashrc

Step 5: Test Connectivity to the Cluster

Run the following commands to verify connectivity and functionality:

• List namespaces:

  kubectl get ns
  

• Get cluster information:

  kubectl cluster-info
  

• List nodes in the cluster:

  kubectl get nodes
  

If the commands return expected results, your Kubectl is successfully configured.

Conclusion

Installing Rancher on a single node using Docker is a straightforward process that provides a powerful platform for managing Kubernetes clusters. By leveraging the Docker Compose file provided above, you can quickly spin up a Rancher instance and start exploring its capabilities.

Official Rancher Documentation - Installing Rancher on a Single Node Using Docker

Official Kubectl Installation Page - Install Kubectl on Linux