Last time we took a try on ansible with the three virtual machines we created with pve. And this time we are going to use ansible to set up a k8s environment with these three virtual machines. I’m going to edit the playbook step by step, following the official installation guide of k8s and docker. All my nodes are running on Ubuntu 20.04.

Starting of the playbook

- name: Kubernetes
  hosts: homelab_vms
  vars_files:
    - homelab.yaml
  become: yes
  tasks:
    - name: Ping my hosts
      ansible.builtin.ping:

This is the starting of the playbook. We are going to use the hosts defined in another yaml file with the password variables storing in the vault. And we are going to use the root account to do the following tasks (defined in become: yes). And first of all we are going to ping the hosts to make sure they are reachable.

Install software require

    - name: apt update
      ansible.builtin.apt:
        update_cache: yes
    - name: Prepare software
      ansible.builtin.apt:
        name: ca-certificates, curl
        state: present

These are defined as two tasks. The first one is to update the apt cache, and the second one is to install the required software.

Install docker

Add docker apt repository

Before we install docker, we need to set up the Docker repository. Afterward, we can install and update Docker from the repository.

To set up the repository, we need to firstly add Docker’s official GPG key, and then add the repository to apt sources.

We first need to create a directory for the keyring, and then download the key to the directory. We followed the documents and example for ansible.builtin.file and ansible.builtin.get_url.

There are lots of guide using the apt_key module to fetch the gpg key and use the key to add the apt repo, but it is deprecated and we should use the ansible.builtin.apt_key module instead.

After we add the repository. We need update the apt cache again to make sure the new repository is available.

    - name: Add Docker apt repository
      block:
        - name: Create keyring directory if not exist
          ansible.builtin.file:
            path: /etc/apt/keyrings
            state: directory

        - name: Get Docker gpg key
          ansible.builtin.get_url:
            url: https://download.docker.com/linux/ubuntu/gpg
            dest: /etc/apt/keyrings/docker.asc

        - name: Add docker apt repository
          ansible.builtin.apt_repository:
            repo: "deb [arch=amd64 signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu focal stable"
            state: present

        - name: apt update
          ansible.builtin.apt:
            update_cache: yes

Install docker

After we add the repository, we can install docker with the ansible.builtin.apt module.

    - name: Install docker
      ansible.builtin.apt:
        name: docker-ce docker-ce-cli containerd.io docker-compose-plugin
        state: present

Install k8s

Installing k8s is similar to installing docker. We need to add the apt repository first, and then install the k8s packages. But, before we add the repository, we need to disable swap.

Disable swap

We can do this with the ansible.builtin.command or the ansible.builtin.shell module. They works almost the same but the ansible.builtin.shell module runs the command through a shell (/bin/sh).

We also need to disable swap in the fstab file. We can use the ansible.builtin.replace module to do this. This module “Replace all instances of a particular string in a file using a back-referenced regular expression”.

    - name: Disable swap
      block:
        - name: Disable SWAP
          # Use shell to perform actions inline
          shell: |
            swapoff -a            

        - name: Disable SWAP in fstab
          replace:
            path: /etc/fstab
            regexp: '^([^#].*?\sswap\s+sw\s+.*)$'
            replace: '# \1'

Add k8s apt repository

Similar to docker, almost the same. And please note that The legacy Linux package repositories apt.kubernetes.io and yum.kubernetes.io have been deprecated and will be frozen starting from September 13, 2023.. Here we are using the new repository.

    - name: Add K8s apt repository
      block:

        - name: get gpg key
          ansible.builtin.get_url:
            url: https://pkgs.k8s.io/core:/stable:/v1.28/deb/Release.key
            dest: /etc/apt/keyrings/kubernetes.asc

        - name: add k8s apt repository
          ansible.builtin.apt_repository:
            repo: "deb [arch=amd64 signed-by=/etc/apt/keyrings/kubernetes.asc] https://pkgs.k8s.io/core:/stable:/v1.28/deb/ /"
            state: present

        - name: apt update
          ansible.builtin.apt:
            update_cache: yes

Install k8s packages

Same as above.

    - name: Install Kubernetes
      apt:
        name: kubectl, kubelet, kubeadm
        state: present

Conclusion

We are done so far. Ansible is really a powerful tool to manage the configuration of multiple machines. Playbook can be clone and run on any machine, and it will automatically set up the environment. It is really convenient and easy to use.