feat: rancher and kubernetes guide (#1812)

* feat: rancher and kubernetes guide

* feat: add headers

Author: alemorvan

docs/guides/containers/img/rancher_cluster_create.png

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+---
+title: Working with Rancher and Kubernetes
+author: Antoine Le Morvan
+contributors: Steven Spencer, Ganna Zhyrnova
+update: 22-Feb-2024
+tested_with: 9.3
+tags:
+  - rancher
+  - kubernetes
+  - containers
+  - docker
+---
+
+# Working with Rancher and Kubernetes
+
+**Kubernetes** (**K8s**) is an open-source container orchestration system for managing the deployment and management of containerized applications.
+
+K8S has made a name for itself on the market, so there's really no need to introduce it anymore.
+
+Cloud providers have made it easy to deploy managed Kubernetes platforms, but what about setting up and managing an on-premises cluster?
+
+How easy is it to manage multiple clusters, whether on-premise or multi-cloud?
+
+The last two questions can be answered in the negative... No, setting up an on-premise cluster isn't easy, and managing a multi-cloud cluster can be a real headache.
+
+That's where the subject of this guide comes in: **Rancher**! Rancher is also an open-source system, enabling the installation and orchestration of several multi-cloud or on-premise clusters, and providing interesting features such as an application catalog and a practical web interface for visualizing resources.
+
+Rancher will enable you to deploy kubernetes clusters managed by cloud providers, import existing kubernetes clusters or deploy K3S (for short, it's a lighter version of K8S) or K8S clusters.
+
+This guide will help you discover Rancher, install and start it, and then create an on-premise kubernetes cluster deployed on RockyLinux servers.
+
+## Rancher deployment
+
+Installing Rancher is quite trivial, as long as you have docker installed on your server.
+
+Docker installation is covered by the gemstone [docker installation](./gemstones/docker/).
+
+To run on a Rocky 9, rancher will also require modules to be loaded.
+
+One way of ensuring that the necessary modules are loaded during system startup is to create a `/etc/modules-load.d/rancher.conf` file with the following contents:
+
+```text
+ip_tables
+ip_conntrack
+iptable_filter
+ipt_state
+```
+
+And the easiest way to apply that changes is to reboot the server: `sudo reboot`.
+
+Once rebooted, you can ensure the modules are loaded thanks to the `lsmod | grep <module_name>` command.
+
+We now have a system ready to receive the rancher container:
+
+```bash
+docker pull rancher/rancher:latest
+docker run -d --name=rancher --privileged --restart=unless-stopped -p 80:80 -p 443:443 rancher/rancher:latest
+```
+
+!!! NOTE
+
+    If you're curious, have a look at the new container's logs. You'll see that a K3S cluster (with a single node) has just been created! This is how rancher works in its standalone version.
+
+    ![k3s local cluster](img/rancher_k3s_local_cluster.png)
+
+As Rancher listens on port 443, open your firewall to allow access from the outside:
+
+```bash
+firewall-cmd --permanent --zone=public --add-service=https
+firewall-cmd --zone=public --add-service=https
+```
+
+If you go to the newly deployed rancher web interface, a message will inform you how to retrieve the admin administrator password which is present in your container logs.
+
+To do this, launch the following command:
+
+```bash
+docker logs rancher  2>&1 | grep "Bootstrap Password:"
+```
+
+You are ready to connect to the Rancher's webUI.
+
+![rancher](img/rancher_login.png)
+
+!!! NOTE
+
+    This solution is by no means production-ready. You'll need to make sure the system is highly available, but it's a good start. Consider deploying Rancher on an existing K8S cluster for optimal HA.
+
+## Kubernetes on RockyLinux 9 servers
+
+Rancher offers its own docker-based version of Kubernetes: RKE (Rancher Kubernetes Engine).
+
+All you need is several RockyLinux servers and the [Docker engine](./gemstones/docker/) installed on them.
+
+Don't forget that one of the requirements of kubernetes is to have an odd number of master nodes (1 or 3, for example). For the purposes of our tests, I propose to start with 3 master nodes and 2 additional nodes with only the worker role.
+
+Once Docker is installed on the servers, stop firewalld and run nftables on each servers:
+
+```bash
+systemctl stop firewalld
+systemctl disable firewalld
+systemctl start nftables
+systemctl enable nftables
+```
+
+We are ready for our cluster creation.
+
+### Cluster creation
+
+In the cluster management area, create a new cluster:
+
+![create cluster](img/rancher_cluster_create.png)
+
+You are free to create a cluster in a hosted Kubernetes provider, provision new nodes and create a cluster using RKE2/K3s, or, and that is our case, use existing nodes and create a cluster using RKE2/K3s.
+
+Choose the last option.
+
+Enter a cluster name and description.
+
+Take your time to discover the various options available before launching cluster creation.
+
+![cluster creation](img/rancher_create_custom_cluster.png)
+
+Once the cluster has been created, go to the Registration tab to add our servers:
+
+![registring hosts](img/rancher_hosts_registration.png)
+
+First, select the various roles of the node you are adding and copy the necessary command line. If your cluster uses a self-signed certificate, check the appropriate box.
+
+Go to the node you wish to add to the configuration and paste the command you copied earlier.
+
+After a few minutes, the server will be added to the cluster, and if it's the first server and has all the roles, the cluster will become available in the web interface.
+
+Once you've added the 5 servers, you should get a result similar to this one:
+
+![clusters hosts](img/rancher_cluster_ready.png)
+
+## Conclusion
+
+Congratulations! You've installed your first kubernetes cluster in just a few minutes/hours, thanks to Rancher's features.
+
+If you're new to kubernetes, you can already be proud of yourself: you're on the right track. You now have everything you need to continue your discovery of kubernetes.