Here are some steps you need to should take when setting up Ansible for the first time.

• Install the software
• Confirm ssh working
• Create a Inventory/Host_file
• Ansible Ping
• Create a playbook
• Confirm the YAML is valid
• Confirm the syntax is valid
• Confirm everything works together

Install the software

First you need to install the Ansible software. On Fedora that is as simple as a dnf install ansible, or on debian apt install ansible.

Confirm ssh working

Confirm that you can connect to the servers via ssh as you would normally.

ssh -i /home/my_user/.ssh/id_ed25519_pi my_user@192.168.0.1
ssh -i /home/my_user/.ssh/id_ed25519_pi your_username@192.168.1.2

Create a Inventory/Host file

Translate the ssh commands into a Inventory/Host file. I am using a YAML in this example but other variants are available.

all:
  hosts:
    my_server:
      ansible_host: 192.168.0.1
    your_server:
      ansible_host: 192.168.1.2
      ansible_ssh_user: your_username
  vars:
    ansible_connection: ssh
    ansible_ssh_user: my_user
    ansible_ssh_private_key_file: /home/my_user/.ssh/id_ed25519_pi

Ansible Ping

Check that your server is up and reported correctly in your file by having Ansible ping it. This should allow you to determine if at least there is a command and control connection available.

ansible --inventory-file my_inventory.yaml -m ping all

This uses the group all and will ping all servers under it. The reply below shows a positive and negative response.

my_server | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": false,
    "ping": "pong"
}
your_server | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 192.168.1.2 port 22: No route to host",
    "unreachable": true
}

The msg will give you a clue as to what is going wrong and you should try to ssh directly with the Ansible credentials again, and then try and ping using Ansible.

ansible --inventory-file my_inventory.yaml -m ping your_server

Modify the Inventory file until you have managed to get a successful reply.

Create a playbook

Work on your playbook and verify that it is valid yaml.

---
- name: Test Ping
  hosts: all
  tasks:
  - action: ping

Confirm the YAML is valid

If there is no reply all is good.

yamllint ~/my_example.yaml

If there is no reply all is good. For your reference I will remove the --- line and this is the response.

yamllint ~/my_example.yaml
/home/user/my_example.yaml
  1:1       warning  missing document start "---"  (document-start)

Confirm the syntax is valid

Then verify that the playbook is sane

ansible-playbook --syntax-check ~/my_example.yaml

If there is no reply all is good. For your reference I will remove the hosts line and this is the response.

ansible-playbook --syntax-check ~/my_example.yaml
ERROR! the field 'hosts' is required but was not set

Confirm everything works together

After that you should be able to run the playbook using.

ansible-playbook --inventory-file my_inventory.yaml ~/my_example.yaml

PLAY [Test Ping] ***************************************************************************************************

TASK [Gathering Facts] *********************************************************************************************
[WARNING]: Platform linux on host my_server is using the discovered Python interpreter at /usr/bin/python, but
future installation of another Python interpreter could change this. See
https://docs.ansible.com/ansible/2.9/reference_appendices/interpreter_discovery.html for more information.
ok: [my_server]
fatal: [your_server]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: ssh: connect to host 192.168.1.2 port 22: No route to host", "unreachable": true}

TASK [ping] ********************************************************************************************************
ok: [my_server]

PLAY RECAP *********************************************************************************************************
my_server                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
your_server                : ok=0    changed=0    unreachable=1    failed=0    skipped=0    rescued=0    ignored=0