In the previous step we discovered and added the IP address of all our nodes to the file on NUC 2: /home/ansible/my-project/hosts

Our first Ansible playbook will be to update Ubuntu packages on all the worker nodes.

Purpose:

• Demonstrate a very useful playbook
• Update all our nodes to the latest code

From NUC 1, log in to the Ansible control node, NUC 2.

Create file /home/ansible/my-project/update.yml

update.yml

---
- hosts: nodes
  become: true
  become_user: root
  tasks:
    - name: Update apt repo and cache on all Debian/Ubuntu boxes
      apt: update_cache=yes force_apt_get=yes cache_valid_time=3600

    - name: Upgrade all packages on servers
      apt: upgrade=dist force_apt_get=yes

    - name: Check if a reboot is needed on all servers
      register: reboot_required_file
      stat: path=/var/run/reboot-required get_md5=no

    - name: Reboot the box if kernel updated
      reboot:
        msg: "Reboot initiated by Ansible for kernel updates"
        connect_timeout: 5
        reboot_timeout: 300
        pre_reboot_delay: 0
        post_reboot_delay: 30
        test_command: uptime
      when: reboot_required_file.stat.exists

ansible-playbook -i hosts update.yml

It's not great, but some servers are inconsistent in resolving DNS names using DHCP.

Here is a quick fix I have used in the past: ansible -i hosts all -a dhclient

This can get you name resolution, but you many have two IP addresses!

Current things to test better solutions:

• sudo netplan apply
• sudo reboot

Congratulations you just updated your nodes! Next is your second Ansible playbook - Ansible Playbook - CMOS.

Set the ethernet interface to be “optional” on the nodes so they will boot faster; they normally wait for the network to come up on the wired interface. Since we are on WiFi only, the interface will never come up.

Steps:

1. Create file /home/ansible/my-project/ethernetoptional.yml

   • ethnetoptional.yml

     ---
     - hosts: nodes
       become: true
       become_user: root
       tasks:
         - name: Set ethernet interface to optional
           lineinfile:
             path: /etc/netplan/00-installer-config.yaml
             insertafter: "dhcp4: true"
             line: "      optional: true"
         - name: Apply netplan
           command: netplan apply
           ignore_errors: true

2. Test the playbook
   • ansible-playbook -i hosts ethernetoptional.yml

Sometimes in my Lab testing I find a NUCs that seem slowing or become unresponsive. This can actually be due to a poor WiFi connection!

1. Create the playbook check-wifi.yml

   • check-wifi.yml

     ---
     - name: Check wifi strength
       hosts: clients
       remote_user: ansible
       become: true
       tasks:
         - name: Make sure wireless-tools is installed
           apt:
             name: wireless-tools
             state: present
         - name: Gather wifi strength
           shell: "iwconfig | grep Quality"
           register: wifi
           changed_when: false
         - name: Display wifi strength
           debug:
             msg: "{{ item }}"
           with_items: "{{ wifi.stdout_lines }}"
         - name: Calculate wifi strength
           set_fact:
             strength: "{{ wifi.stdout | regex_search(regexp, '\\1') }}"
           vars:
             regexp: 'Quality=([0-9]+)/70'
         - name: Show value
           debug:
             msg:
               - "{{ strength[0] }}/70 = {{( ( (strength[0] | int) / 70) * 100 ) | int }}%"

2. Run it: ansible-playbook -i hosts check-wifi.yml
3. If all the NUCs are in the same place but one is much weaker than the others
   • check the antennas are connected to the Wifi card
   • does a different wifi card improve the connection?