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Wednesday, 25 September 2019

Kubernetes cluster (K3S) running in 5 min

Kubernetes cluster (K3S) running in 5 min

Setting up Kubernetes can be a procedure that takes some time, but with the Kubernetes distribution K3S and a Ansible playbook we can get a Kubernetes cluster up and running within 5min.

So I created just that, an Ansible playbook where you just add your nodes to a inventory file and then the playbook will install all the dependencies we need for K3S, the workers will automaticly join the master AND I have also added some firewall rules (with help from UFW) so you have some basic protection for your servers. Let’s go through how to use it.

Requirements

  • Git
  • Virtualenv (Python) on the computer you will deploy this from.
  • At least 2 servers with SSH access.
    • Must be based on Ubuntu.
    • User with sudo permissions.
    • Must have docker installed.

Preparations

  • Point a hostname to the server you want to be your kubernetes_master_server.

Steps

Step 1

Prepare your local environment (or wherever you deploy this from) with the dependencies we need. This will install a Virtual Python environment and download Python, Pip and Ansible and make those available in your $PATH so you can execute them.

  1. Clone the K3S Ansible repository from Github.

     $ git clone git@github.com:pixelpiloten/k3s-ansible.git
    
  2. Go to the ansible directory and create your Virtual Python environment.

     $ virtualenv venv
    
  3. Activate the Virtual Python environment.

     $ source venv/bin/activate
    

Step 2

Configure your inventory file with the servers you have, you can add how many workers you want but there can only be one master in K3S (though it might be supported in the future).

  1. Rename the inventory.example file to inventory.

     $ mv inventory.example inventory
    
  2. Change the kubernetes_master_server to the server you want to be your Kubernetes master and add ip(s) to the allowed_kubernetes_access list for the ips that should have access to the cluster via Kubectl. Alsop change ansible_ssh_host, ansible_ssh_user, ansible_ssh_port, ansible_ssh_private_key_file and hostname_alias to your server login details. And of course add how many workers you have.

     all:
     vars:
       ansible_python_interpreter: /usr/bin/python3
       kubernetes_master_server: https://node01.example.com:6443 # Change to your master server
       allowed_kubernetes_access: # Change these to a list of ips outside your cluster that should have access to the api server.
         - 1.2.3.4
         - 1.2.3.5
     children:
       k3scluster:
         hosts:
           node01: # We can only have one master.
             ansible_ssh_host: node01.example.com
             ansible_ssh_user: ubuntu
             ansible_ssh_port: 22
             ansible_ssh_private_key_file: ~/.ssh/id_rsa
             hostname_alias: node01
             kubernetes_role: master # Needs to be as it is.
             node_ip: 10.0.0.1
           node02: # Copy this and add how many workers you want and have.
             ansible_ssh_host: node02.example.com
             ansible_ssh_user: ubuntu
             ansible_ssh_port: 22
             ansible_ssh_private_key_file: ~/.ssh/id_rsa
             hostname_alias: node02
             kubernetes_role: worker # Needs to be as it is.
             node_ip: 10.0.0.2
    

Step 3

You are now ready to install K3S on your servers. The Ansible playbook will go through the inventory-file and install the dependencies on your servers and then install K3S on your master and your workers, the workers will automaticly join your K3S master. At the end the playbook will write a Kubeconfig-file to /tmp/kubeconfig.yaml on the machine you are running the playbook on.

  1. Run the Ansible playbook and supply the sudo password when Ansible asks for it.

     $ ansible-playbook -i inventory playbook.yml --ask-become-pass
    
  2. When the playbook is done you can copy the Kubeconfig-file /tmp/kubeconfig.yaml to your ~/.kube/config or where ever you want to keep it, BUT you need to modify the the server hostname to whatever your kubernetes_master_server is. (PS. Do not use the content below, use the /tmp/kubeconfig.yaml that got generated locally)

     apiVersion: v1
     clusters:
     - cluster:
         certificate-authority-data: <REDACTED-CERTIFICATE>
         server: https://0.0.0.0:6443
     name: default
     contexts:
     - context:
         cluster: default
         user: default
     name: default
     current-context: default
     kind: Config
     preferences: {}
     users:
     - name: default
     user:
         password: <REDACTED-PASSWORD>
         username: admin
    

Tadaa!

So you have now created a K3S Kubernetes cluster, gotten the Kubeconfig and added magic firewall rules so only you have access. And if you need to add more workers after the first initial setup you can just add more workers to the inventory-file and run the playbook in Step 3.1 again.

So walk like a baws down the office corridor with your elbows high and call it a day!

You done did it Baws!