Now that you have your Stack of NUCs all built, updated, and connected to the wireless network, it is time to set them up in the Ansible inventory.

Purpose:

• Discover local hosts that the Ansible control node can access
• Add these hosts (nodes) to our inventory
• Test access to the nodes using Ansible

Power on all the NUCs. WiFi connectivity should make all visible to NUC 2, the Ansible control node.

Run the following discovery script from the Ansible control node (NUC 2), and add the IP address to the inventory file ('hosts'). Copy the file to /home/ansible/my-project/discover.sh

discover.sh

if [ "$#" -ne 1 ]
then
  echo "Usage: $0 filename.txt"
  echo "results will be appended to this file"
  exit 1
fi
OUTPUT=$1
[[ ! -z "$OUTPUT" ]] && touch $OUTPUT || exit
IPs=$(sudo arp-scan --localnet --numeric --quiet --ignoredups | grep -E '([a-f0-9]{2}:){5}[a-f0-9]{2}' | awk '{print $1}')
for i in ${IPs}; do
  # set up SSH managment keys
  ssh-keygen -q -R $i && ssh-keyscan -H $i >> ~/.ssh/known_hosts
  # identify hosts ansible can access
  ssh -q -o PasswordAuthentication=No $i "hostname -I" && echo $i && echo $i >> $OUTPUT
done

Next, run the file: bash discover.sh hosts

This will find all the live hosts on the network, tried to SSH to all of them, added keys to the known_files file, and adding IP addresses of the Ansible worker notes to the “hosts” file.

This is a quick and easy way to determine which ones weren't discovered: power off the ones that are working. Any of the NUCs still powered on has now been discovered.

ansible -i hosts all -a “poweroff”

Pull these NUCs for re-imaging/investigation. Next, power the “good” NUCs back on.

You now have a working Ansible environment! Continue to our First Ansible playbook with Ansible Playbook - Update.

You can discover ssh servers using nmap.

1. Install nmap
   • sudo apt install nmap -y
2. Run the following scan, replacing the network 192.168.1.0/24 with your Lab network
   • nmap -p 22 –open -sV 192.168.1.0/24
3. You can see that all the NUCs you installed have the same OpenSSH version. Add these IP addresses to the hosts file under [nodes]
   • You will still need to add the hosts to the known hosts file

Another way to discover the NUCs on the network quickly and easily is to use lldp.

NOTE: lldp is a standards-based neighbor discovery protocol similar to Cisco CDP. It works fine over wired network connections. However, in my experience wireless routers and access points don't support lldp between wireless clients, so I have not included this in the lab.

To use lldp in a wired lab

• add the lldpd to the list of packets to install using apt
• install on NUC 1 using sudo apt install lldpd
• from NUC 1 run lldpcli show neighbors