Setup Kubernetes cluster with K3sup

Setup Kubernetes cluster with k3sup

Pre Requirements for Raspberry PI

k3sup

k3sup is an application that simplifies k3s cluster configuration. We can use the “install” command to configure a master node and the “join” command to set up workers node one by one.

Requirements

1. We need SSH access with a public-key authentication method from the server running k3sup to the nodes that we want to install k3s to set up a cluster. To use Ansible to copy authorized_keys to nodes [link].

2. The user on the nodes can execute the “sudo” command without typing a password.

   # to configure NOPASSWD sudo 
   sudo visudo

   And add the following

   <username> ALL=(ALL) NOPASSWD: ALL

Installation

curl -sLS https://get.k3sup.dev | sh
sudo install k3sup /usr/local/bin/

#k3sup --help

Create a master node

# here we can also use --host if we want to provide hostname instead of IP address
k3sup install --ip <ip_of_master_node> --user <user_for_ssh>

Create a worker node

# here we can replace ip with host, ex: --host, --server-host respectively
k3sup join --ip <worker_node_ip> --server-ip <master_node_ip> --user <worker_node_ssh_user>

Cleanup cluster

1. For worker nodes

   # ssh into nodes and run this command. the command is located in /usr/local/bin
   k3s-killall.sh
   k3s-agent-uninstall.sh
   

   # incase k3s-agent-uninstall fail to remove this directory
   sudo rm -rf /var/lib/kubelet

2. For master node

   # ssh into nodes and run this command. the command is located in /usr/local/bin
   k3s-killall.sh
   k3s-uninstall.sh

Node: Use Ansible to remove k3s from cluster

Install kubectl

curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl

Load kubeconfig file

export KUBECONFIG=/home/ubuntu/kubeconfig
kubectl config set-context default

Save kubeconfig to user directory

kubectl config view --raw > ~/.kube/config

Check cluster

kubectl get node -o wide

Shell script

#!/bin/sh
k3sup install --host red --user pi
k3sup join --host yellow --server-host red --user pi
k3sup join --host black --server-host red --user pi
k3sup join --host green --server-host red --user pi

export KUBECONFIG=/home/ubuntu/kubeconfig
kubectl config set-context default
kubectl config view --raw > ~/.kube/config