ansible.md

Ansible

Ansible is a provisioning and configuration automation tool that can be used to install and config software on multiple remote hosts.

This is ideal for use with our K3s cluster as we can remotely perform operations and install software on the Ubuntu hosts without needing to log into each Raspberry Pi individually and run things manually.

Creating Host Inventory

The Ansible How to build your inventory documentation covers everything you need to know about creating inventory so that Ansible knows where to locate your hosts, and the groups they belong to when running roles.

At the most basic level I have the below contents within the /etc/ansible/hosts file on my Mac laptop.

k3s-1 ansible_connection=ssh ansible_user=ubuntu
k3s-2 ansible_connection=ssh ansible_user=ubuntu
k3s-3 ansible_connection=ssh ansible_user=ubuntu

[k3s-nodes]
k3s-[1:3]

[k3s-master]
k3s-1

[k3s-workers]
k3s-[2:3]

That file contains the following items:

• the list of hostnames for each remote host, I have mapped the ip addresses to the hostnames in my /etc/hosts file already.
• when making connections via ssh the ubuntu user will be the user account logged into on the remote host
• the k3s-nodes group can be used when running Ansible roles, or adhoc commands, to execute these on all hosts
• the k3s-master group can be used to run things only on the master node
• the k3s-workers group can be used to run things only on the worker nodes

SSH Access

As commands are run over ssh you may need to add your public ssh key of your local machine to each remote host for trusted password-less access. You can run the below command against each host. You will need to provide the password for the remote host when prompted.

ssh-copy-id ubuntu@k3s-1

Pinging Hosts to Verify Connectivity

To verify that the hosts are contactable and that Ansible is able to access all nodes in the k3s-nodes group the Ansible ping module can be used.

$ ansible k3s-nodes -m ping

k3s-2 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}
k3s-1 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}
k3s-3 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}

Running Adhoc Commands

Adhoc commands can be run against the nodes for performing single tasks. For example, the below command will add a cron job so that a Python script is executed whenever the node starts up.

See the Ansible Introduction to ad hoc commands for more information on this.

ansible k3s-nodes -u ubuntu \
  -m cron \
  -a 'name="start rpi oled display" special_time=reboot job="sudo python3 /home/ubuntu/src/github/yahboom-raspi-cooling-fan/oled.py &"'

k3s-2 | CHANGED => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": true,
    "envs": [],
    "jobs": [
        "start rpi oled display"
    ]
}
k3s-1 | CHANGED => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": true,
    "envs": [],
    "jobs": [
        "start rpi oled display"
    ]
}
k3s-3 | CHANGED => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": true,
    "envs": [],
    "jobs": [
        "start rpi oled display"
    ]
}