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Setting Up k3s for Rancher Integration

Introduction

Prepare your Ubuntu server for Rancher deployment by installing k3s, a lightweight Kubernetes distribution ideal for simplified cluster management. This setup ensures minimal resource usage while providing a robust environment for Rancher.

After completing this guide, you will have:

  • Installed k3s on your Ubuntu server, ready for Rancher.
  • Configured your local environment for seamless k3s cluster management.

Table of Contents

Prerequisites

Before starting, ensure you have:

  1. An Ubuntu server set up and secured. For instructions, refer to "How to Set Up and Secure Your Ubuntu Server"
  2. Terminal or SSH client access to your local machine.

Step 1 - Installing and Verifying k3s

Before initiating the installation of k3s, it's imperative to establish a secure connection to your Ubuntu server:

ssh root@{{ip_address}}

Ensure to replace {{ip_address}} with the actual IP address of your server.

Once a secure connection is established, you can proceed with the k3s installation. It's crucial to consult the SUSE Rancher support matrix to verify compatibility with your intended k3s version. The highest supported version at this time is v1.27. For a detailed list of available versions, visit the list of k3s versions.

To install k3s, execute the following command, ensuring you adjust the version number as needed to match the version compatible with your setup:

curl -sfL https://get.k3s.io | INSTALL_K3S_VERSION=v1.27.14+k3s1 sh -s - server --cluster-init

After the installation completes, verify that your cluster is operational:

k3s kubectl get nodes
k3s kubectl get pods --all-namespaces

You should see nodes marked as Ready, and pods should be in Running or Completed states, indicating that k3s is installed and functioning correctly on your server.

Step 2 - Transferring the kubeconfig File

Transfer the kubeconfig file to manage the cluster remotely:

scp root@{{ip_address}}:/etc/rancher/k3s/k3s.yaml ~/.kube/k3s-murm-rancher.yaml

Replace {{ip_address}} with your server's actual IP. This step is crucial for remote cluster administration.

Step 3 - Setting Up DNS for the Server

Before customizing your kubeconfig file, ensure your server is accessible via a DNS name. This involves adding an A record in your DNS management interface pointing to your server’s IP address.

  • Log in to your DNS provider's management console.
  • Navigate to the DNS settings section for your domain.
  • Add an A record with the following details:
    • Host: The subdomain or prefix you wish to use (e.g., k3s or rancher).
    • Points to: The IP address of your Ubuntu server.
    • TTL: For A Record, 3600 seconds is recommended.

This DNS setup facilitates access to your server using a memorable URL instead of an IP address. Most importantly, if DNS is not used, the backup and restore processes will not work if the IP address changes.

Step 4 - Customizing the kubeconfig File

In this step we will customize the kubeconfig file for easier identification and management of the cluster.

First, update the server URL in the kubeconfig file to point to your server's DNS name. Ensure you replace {{server_dns_name}} with your server's DNS name:

perl -pi -e "s/127.0.0.1/{{server_dns_name}}/g" ~/.kube/k3s-murm-rancher.yaml

Next, change all instances of the default context, cluster, and user names to k3s-murm-rancher to reflect your specific Rancher setup. This naming convention makes managing multiple clusters more intuitive:

perl -pi -e "s/default/k3s-murm-rancher/g" ~/.kube/k3s-murm-rancher.yaml

Step 5 - Merging Configuration Files for Cluster Management

To streamline the management of multiple Kubernetes clusters, integrate your kubeconfig files:

Set the KUBECONFIG environment variable to encompass both your original and the new k3s kubeconfig files:

export KUBECONFIG=~/.kube/config:~/.kube/k3s-murm-rancher.yaml

Then, merge these configurations into one unified file:

kubectl config view --merge --flatten > ~/.kube/merged_kubeconfig

Proceed by backing up your original config file. Afterward, replace it with the newly merged configuration:

mv ~/.kube/config ~/.kube/config_backup
mv ~/.kube/merged_kubeconfig ~/.kube/config
chmod 600 ~/.kube/config

Next, confirm your ability to connect to the k3s cluster while ensuring there's no disruption with the configurations of any existing clusters. Begin by listing the current contexts to view all available clusters:

kubectl config get-contexts

Switch to your k3s cluster's context to verify connectivity:

kubectl config use-context k3s-murm-rancher

Check the resources across all namespaces to ensure the cluster is responsive:

kubectl get all --all-namespaces

Wrap up the process by deleting the unnecessary k3s kubeconfig file:

rm ~/.kube/k3s-murm-rancher.yaml

Conclusion

Your Ubuntu server is now equipped with k3s, creating a solid foundation for deploying Rancher.

Go to Section 3 - Setting up Rancher.