RHEL has ansible-core, podman, and ansible-navigator in the OS repositories.

Ubuntu needs a PPA:

sudo add-apt-repository --yes --update ppa:ansible/ansible
sudo apt install ansible -y

It can also be installed with Python

sudo apt install python3-pip -y
pip3 install ansible

The config is read from: ANSIBLE_CONFIG, ./ansible.cfg, ~/ansible.cfg, /etc/ansible/ansible.cfg

Ansible will not automatically load a config file from the current working directory if the directory is world-writable.

[defaults]
inventory = ./ansible_hosts  # relative to path of ansible.cfg
nocows = True
interpreter_python = /usr/bin/python3
gathering = False
forks = 2
strategy = free
host_key_checking = False

[ssh_connection]
pipelining = True
ssh_args = -o ControlMaster=auto -o ControlPersist=60s

The default inventory path is /etc/ansible/hosts

genpurpose1host.localdomain  # ungrouped

[web]
webserver1 ansible_host=webserver1.localdomain ansible_port=2022 ansible_user=webadmin
localhost ansible_connection=local

[worker]
worker1

[app:children]
web
worker

[all:vars]
ansible_connection=ssh
ansible_ssh_user=myuser
ansible_ssh_private_key_file=my_ssh_key
#ansible_ssh_pass=mypass
#ansible_become_pass=mypass

# Before Ansible 2.0, ansible_user was ansible_ssh_user

For ad-hoc execution:

ansible localhost -m ansible.builtin.gather_facts  # Test

ansible -i inventory all -m shell -a 'echo "A"'  # Execute a shell command

ansible -a 'some_command'  # The module defaults to "command" (instead of "shell")

ansible -i inventory all -m shell -a 'echo "A"' --limit server1  # To run only on server 1 

# -f 5  # To run 5 tasks at a time

For playbook execution:

ansible-playbook playbook1.yaml

---
- name: Play 1
  become: true
  hosts: all
  tasks:
  
    - name: Task 1
      yum_repository:
        name: epel
        description: epel yum repo
        baseurl: https://download.fedoraproject.org/pub/epel/$releasever/$basearch/
        gpgcheck: no
  
    - name: Task 2
      dnf:
        name: httpd
        state: latest  # present|absent|latest

    - name: Task 2
      dnf:
        name: 
          - net-tools
          - bind-utils
          - telnet
          - nmap
          - vim-enhanced
          - sysstat
          - tuned
          - numactl
  
    - name: Task 3
      dnf: name=http://example.com/some_package.rpm
  
    - name: Task 4
      apt_repository:
        repo: deb http://archive.canonical.com/ubuntu hardy partner
        state: present
  
    - name: Task 5
      apt:
        name: foo
        update_cache: yes
        state: present
  
    - name: Task 6
      apt:
        deb: https://example.com/some_package.deb
  
    - name: Task 7
      copy:
        src: file1
        dest: /tmp/file1
        remote_src: true
  
    - name: Task 8
      template:
        src: file1.j2
        dest: /tmp/file1
      vars:
        var1: 1
  
    - name: Task 8
      shell: |
        command1
        command2
  
    - name: Task 7
      file:
        path: /tmp/dir1
        state: directory
        owner: root
        group: root
        mode: "0777"
  
    - name: Task 8
      sysctl:
        name: net.ipv4.ip_forward
        value: '1'
        sysctl_set: true
        state: present
        reload: true
  
    - name: Task 8
      get_url:
        url: http://example.com
        dest: /tmp/file1
      environment:
        http_proxy: https://example.com:8080
        https_proxy: https://example.com:8080
  
    - name: Task 6
      local_action: echo "Hello"
  
    - name: Task 6
      script: /tmp/script1
  
    - name: Task 6
      lineinfile:
        path: /tmp/file1
        regexp: '^db=$'
        line: db=localhost
      
        

# Tasks to get the output from one command and use as conditional for another command

- name: Check ping
  delegate_to: srv1
  shell: ping -c 1 somehost
  register: reachableping
  ignore_errors: true

- name: Do something
  delegate_to: srv1
  shell: ./run_cmd_1
  ignore_errors: true
  when: "'100.0% packet loss' in reachableping.stdout"

# Variables can be used for an entire block

- name: Demonstrate environment variable in block
  hosts: localhost
  connection: local
  gather_facts: false
  vars:
    motd: Hello World
  tasks:
  - block:

    - name: Print variable
      shell: "echo $motd"
      register: theoutput

    - debug: var=theoutput.stdout
      environment:
        motd: "{{ motd }}"