Kubernetes Recipe - RKE | Evocative Development

Introduction

One of the challenges at the beginning of learning Kubernetes is installing it. Due to Kubernetes documentation, there are limited ways [REF]:

Learning Environment
- Kind
- Minikube
Production Environment
- kubeadm
- kops
- Kubespray

However, according to CNCF, there are many open source Kubernetes distributions and tools to set up Kubernetes. RKE is one of the installation tools that helps you install your Kubernetes cluster with ease. You can also install a single node for your learning environment.

Note: Lots of texts introduce Minikube for learning env. However, in my opinion, even for installation, it has many challenges. Even for learning env, I recommend using a single node by RKE.

Installing a K8S Cluster

Note: in this text, laptop means your working workstation or computer, which is used to set up k8s on the node(s).

On Laptop

Create SSH key
- ssh-keygen -t rsa -b 4096 -f ~/.ssh/rke
  - $HOME/.ssh/rke - SSH private key, keep this secure
  - $HOME/.ssh/rke.pub - SSH public key, copy this to nodes
  - Setting passphrase is optional.
Install kubectl (and add it to the PATH) [REF]
- apt-get update && sudo apt-get install -y apt-transport-https gnupg2 curl
- curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
- echo "deb https://apt.kubernetes.io/ kubernetes-xenial main" > /etc/apt/sources.list.d/kubernetes.list
- apt-get update && apt-get install -y kubectl

Prepare your Node(s)

On each node

Check your hostname and assert /etc/hosts
Disable Swap
- swapoff -a
- Remove any swap entry from /etc/fstab
Install SSH server
Install Docker CE
Create user rke
- adduser rke
- usermod -aG docker rke
Install your laptop’s public ssh key (rke.pub)
- cat ~/.ssh/rke.pub | ssh rke@NODE "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys"

Run RKE

On the laptop:

[Optional] If you have set the passphrase, install ssh-agent and run it
- eval $(ssh-agent)
- ssh-add, and enter your passphrase
Test your SSH connection to your node(s)
- ssh -i ~/.ssh/rke rke@NODE - SSH login without asking rke’s password
Download RKE Release, rename it to rke, and set it in PATH
rke config
- Answer the questions to setup your k8s cluster
- It creates a cluster.yml
- Modify cluster.yml
  - [Optional] Prepend all system_images with your private registry
  - [Optional] Set ssh_agent_auth to true if you set passphrase
- rke config -s - list all images for download and store in your private registry
rke up
- It’ll show Finished building Kubernetes cluster successfully
- A kube_config_cluster.yml is created which is kubectl config file
kubectl --kubeconfig=kube_config_cluster.yml cluster-info
Run kubectl without --kubeconfig
- export KUBECONFIG=$(pwd)/kube_config_cluster.yml
- mkdir -p ~/.kube && cp -f kube_config_cluster.yml ~/.kube/config && chmod 600 ~/.kube/config

Here is a simple rke config questionnaire:

(*) [+] Cluster Level SSH Private Key Path [~/.ssh/id_rsa]: ~/.ssh/rke
    [+] Number of Hosts [1]: 
(*) [+] SSH Address of host (1) [none]: r1
    [+] SSH Port of host (1) [22]: 
    [+] SSH Private Key Path of host (r1) [none]: 
    [-] You have entered empty SSH key path, trying fetch from SSH key parameter
    [+] SSH Private Key of host (r1) [none]: 
    [-] You have entered empty SSH key, defaulting to cluster level SSH key: ~/.ssh/rke
(*) [+] SSH User of host (r1) [ubuntu]: rke
    [+] Is host (r1) a Control Plane host (y/n)? [y]: 
(*) [+] Is host (r1) a Worker host (y/n)? [n]: y
(*) [+] Is host (r1) an etcd host (y/n)? [n]: y
    [+] Override Hostname of host (r1) [none]: 
    [+] Internal IP of host (r1) [none]: 
    [+] Docker socket path on host (r1) [/var/run/docker.sock]: 
    [+] Network Plugin Type (flannel, calico, weave, canal) [canal]: 
    [+] Authentication Strategy [x509]: 
    [+] Authorization Mode (rbac, none) [rbac]: 
    [+] Kubernetes Docker image [rancher/hyperkube:v1.19.3-rancher1]: 
    [+] Cluster domain [cluster.local]: 
    [+] Service Cluster IP Range [10.43.0.0/16]: 
    [+] Enable PodSecurityPolicy [n]: 
    [+] Cluster Network CIDR [10.42.0.0/16]: 
    [+] Cluster DNS Service IP [10.43.0.10]: 
    [+] Add addon manifest URLs or YAML files [no]: 

Only questions with (*) mark are answered, others are passed with default.
Line 21, Cluster IP Range [10.43.0.0/16] is IP range for Services
- Line 24, DNS service’s IP is in the Cluster IP range.
Line 23, CIDR [10.42.0.0/16] is IP range for Pods

Now, some parts of a single-node cluster.yml

nodes:
- address: r1
  port: "22"
  internal_address: ""
  role:
  - controlplane
  - worker
  - etcd
  hostname_override: ""
  user: rke
  docker_socket: /var/run/docker.sock
  ssh_key: ""
  ssh_key_path: ~/.ssh/rke
  ssh_cert: ""
  ssh_cert_path: ""
  labels: {}
  taints: []
services:
  ...
network:
  plugin: canal
  ...
...
ssh_key_path: ~/.ssh/rke
ssh_cert_path: ""
ssh_agent_auth: false 
...

Test Cluster

Create file rancher-demo-deployment.yml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: rancher-demo-dpl
spec:
  replicas: 1
  selector:
    matchLabels:
      app: rancher-demo
  template:
    metadata:
      labels:
        app: rancher-demo
    spec:
      containers:
        - name: rancher-demo
          image: superseb/rancher-demo

---

apiVersion: v1
kind: Service
metadata:
  name: rancher-demo-srv
spec:
  selector:
    app: rancher-demo
  ports:
    - name: rancher-demo
      protocol: TCP
      port: 8080
      targetPort: 8080

---

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: rancher-demo-ingress
spec:
  rules:
    - http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: rancher-demo-srv
                port: 
                  number: 8080

kubectl --kubeconfig=kube_config_cluster.yml apply -f rancher-demo-deployment.yml
kubectl --kubeconfig=kube_config_cluster.yml get all -o wide
Open http://r1/