Build Kubernetes Cluster Using RKE2

RKE2, also known as RKE Government, is Rancher’s next-generation Kubernetes distribution. RKE2, the successor to RKE1, was developed to address limitations in the original Rancher Kubernetes Engine and align better with modern Kubernetes standards. Importantly, RKE2 does not rely on Docker as RKE1 does. RKE1 leveraged Docker for deploying and managing the control plane components as well as the container runtime for Kubernetes. RKE2 launches control plane components as static pods, managed by the kubelet. The embedded container runtime is containerd.

Here are key reasons why RKE2 is preferred over RKE1 for most use cases:

1. Full Kubernetes Compliance

RKE2 is a CNCF-certified Kubernetes distribution, meaning it strictly adheres to upstream Kubernetes standards. This ensures better compatibility with the Kubernetes ecosystem.
RKE1, while functional, had some proprietary implementations and bundled configurations, making it less compliant with upstream Kubernetes practices.

2. Improved Security

RKE2 includes SELinux support and uses containerd (instead of Docker) as the container runtime by default, which enhances security and aligns with Kubernetes’ deprecation of Docker as a runtime.
Built-in support for FIPS 140-2 compliance is available in RKE2, making it a better choice for organizations with strict security requirements.
All system components in RKE2 (e.g., kubelet, etcd, controller-manager) run as non-root where possible, reducing attack surfaces.

3. Simplified Architecture

RKE2 is essentially k3s for production, designed to be lightweight while still supporting enterprise-grade features. It consolidates the architecture by leveraging k3s’ simplicity and modular design.
RKE1 uses Docker Compose to manage Kubernetes components, which can be more complex and error-prone, especially in large-scale deployments.

4. Native High Availability (HA)

RKE2 natively supports HA out of the box with minimal configuration. It integrates seamlessly with multiple control plane nodes and distributed etcd setups.
In RKE1, setting up HA requires manual configuration, external load balancers, and more effort.

5. Extensible Add-ons

RKE2 uses Helm Charts and manifests for managing built-in components and optional features (e.g., ingress controllers, CNI, etc.).
RKE1 has a more rigid structure for integrating add-ons, making customization more challenging.

6. Long-Term Viability

Rancher is focusing its development and support efforts on RKE2 as the go-to Kubernetes distribution for its ecosystem. RKE1 is no longer actively developed and will not receive future updates or new features.

7. Better Cloud-Native Integrations

RKE2 is designed with cloud-native patterns in mind, making it easier to integrate with cloud providers, external storage, and networking solutions.
RKE1 predates many of these advancements and is less flexible in modern environments.

8. Edge and IoT Use Cases

Leveraging its k3s heritage, RKE2 is highly optimized for edge computing and resource-constrained environments, while still supporting traditional data centers and cloud setups.
RKE1 is heavier and more suitable for on-premises or traditional data center use.

When to Use RKE1?

RKE1 may still be a good fit in limited scenarios:

Legacy Systems: If your infrastructure is already using RKE1 and migrating to RKE2 isn’t immediately feasible.
Docker Dependency: If your workflows depend heavily on Docker as the container runtime (though this should change as Kubernetes has deprecated Docker).

Key Differences Summary

Feature	RKE1	RKE2
Kubernetes Compliance	Partial	Fully CNCF-compliant
Security	Basic	Enhanced (SELinux, FIPS, rootless, etc.)
Container Runtime	Docker	containerd (default)
Architecture	Docker Compose-managed	Simplified, native Kubernetes components
HA Support	Manual	Native, automatic
Target Use Cases	Data center focus	Cloud, edge, and on-premises
Long-Term Support	Limited (deprecated focus)	Actively developed and supported

Why Choose RKE2 Today?

RKE2 offers a modern, secure, and efficient Kubernetes platform that aligns with both current and future Kubernetes standards. With active development, better performance, and enhanced security, RKE2 is the logical choice for production deployments and new projects.

Prerequisites:

A Linux-based OS (e.g., Ubuntu, CentOS, etc.)
At least two nodes (one for the master and one for the worker) or multiple worker nodes in a cluster
Sudo/root privileges on all nodes
Network connectivity between the nodes

1. Install RKE2 on the Nodes

RKE2 is installed via a simple script. Here’s how to install RKE2 on the nodes.

On Master Node:

Run the following commands to install RKE2:

curl -sfL https://get.rke2.io | sh -

This installs RKE2 and its required components.

On Worker Nodes:

Repeat the same process on the worker nodes to install RKE2.

2. Start RKE2 on the Master Node

Once the installation is complete, you need to start the RKE2 server (master node) on the master node:

sudo systemctl enable rke2-server.service
sudo systemctl start rke2-server.service

3. Join Worker Nodes to the Cluster

To add worker nodes to the cluster, you need to provide the master node’s token and the URL of the master node.

On the Worker Node:

First, retrieve the RKE2 token from the master node: sudo cat /var/lib/rancher/rke2/server/node-token
Join the worker node to the master node using the following command (replace <MASTER_NODE_IP> with the actual IP address of the master node): sudo rke2 agent --server https://<MASTER_NODE_IP>:9345 --token <NODE_TOKEN>

4. Check the Cluster Status

Once the worker nodes are joined to the cluster, you can verify the status of the cluster. On the master node, run:

sudo kubectl get nodes

This will show all the nodes in the cluster, including the master and worker nodes.

5. Configure kubectl Access

To interact with the Kubernetes cluster from your local machine or a different node, you need to configure kubectl access. The master node stores the kubeconfig file, which contains the credentials for accessing the cluster.

You can download the kubeconfig file from the master node to your local machine:

sudo cat /etc/rancher/rke2/rke2.yaml

Copy the contents of the file and save it as config on your local machine in the ~/.kube directory. Set the KUBEV2_CONFIG environment variable to point to this file:

export KUBEV2_CONFIG=~/.kube/config

Now, you can use kubectl to interact with the cluster.

6. Managing the Cluster

RKE2 provides several systemd services to manage the cluster.

Check the status of RKE2 services: sudo systemctl status rke2-server
Restart RKE2 services: sudo systemctl restart rke2-server
Stop RKE2 services: sudo systemctl stop rke2-server

7. Deploy Applications

Once your cluster is up and running, you can deploy applications using kubectl. For example, to deploy a simple Nginx pod:

kubectl create deployment nginx --image=nginx
kubectl expose deployment nginx --port=80 --type=NodePort

This will create a deployment and expose it on a NodePort.

8. RKE2 Configuration (Optional)

You can customize RKE2’s settings by editing the /etc/rancher/rke2/config.yaml file. For example, to enable persistent storage, logging, or monitoring, you can add configurations in this file.

Example:

token: <NODE_TOKEN>
selinux: false

After modifying the configuration, restart RKE2 to apply changes:

sudo systemctl restart rke2-server

9. Updating RKE2

To upgrade RKE2 to a new version, you can run the upgrade script:

curl -sfL https://get.rke2.io | sh -

It will automatically upgrade the RKE2 components while maintaining the cluster’s state.

10. Uninstalling RKE2

To uninstall RKE2, run the following commands:

sudo systemctl stop rke2-server
sudo systemctl disable rke2-server
sudo rm -rf /etc/rancher/rke2
sudo rm -f /usr/local/bin/rke2

Additional Resources

Official Documentation: RKE2 Docs
RKE2 GitHub: RKE2 GitHub
Rancher Forums: Rancher Community
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