Ansible - Inventory 🧳

Description 👀

Ansible can work with one or more systems in your infrastructure at the same time. In order to work with multiple servers Ansible needs to establish a connection to those servers. This is done with SSH on linux, and Powershell Remoting for Windows. Most of the pitfalls for other orchestration tools is that you are required to set up an agent on the target machines before you can invoke any automation. This is not the case with Ansible. Ansible is agentless, meaning no additional software is needed on the target machines to be able to work with Ansible.

Information about the target machines is stored in an inventory. The inventory is a file that contains a list of hosts and groups of hosts. The inventory file is located in the /etc/ansible/hosts directory by default.

Basic `Commands` 📝

ping to test inventory

  ansible <host-or-group> -m ping -i <inventory-config-file>

Examples 🧩

basic inventory file

  server1.company.com
  server2.company.com
  server3.company.com
  server4.company.com

basic inventory file with aliases

  web ansible_host=server1.company.com
  db ansible_host=server2.company.com
  mail ansible_host=server3.company.com
  web2 ansible_host=server4.company.com

some other inventory parameters that can be used:
```
ansible_port=22
ansible_user=ansible
ansible_ssh_pass=ansible
ansible_connection=ssh 
```
- by default the ansible port is set to 22
- by default the ansible user is set to root (on linux)
- if you dont have any other hosts to connect to then you can use localhost instead
```
  localhost ansible_connection=localhost
```

basic inventory file with groups

  [web]
  server1.company.com
  server2.company.com

  [db]
  server3.company.com
  server4.company.com

inventory file with linux web servers and windows db servers

  web1 ansible_host=server1.company.com ansible_connection=ssh ansible_user=root ansible_ssh_pass=Password123!
  web2 ansible_host=server2.company.com ansible_connection=ssh ansible_user=root ansible_ssh_pass=Password123!
  web3 ansible_host=server3.company.com ansible_connection=ssh ansible_user=root ansible_ssh_pass=Password123!
  db1 ansible_host=server4.company.com ansible_connection=winrm ansible_user=administrator ansible_password=ansible_password=Password123!

grouping the servers

  # -- servers
  # web servers
  web1 ansible_host=server1.company.com ansible_connection=ssh ansible_user=root ansible_ssh_pass=Password123!
  web2 ansible_host=server2.company.com ansible_connection=ssh ansible_user=root ansible_ssh_pass=Password123!
  web3 ansible_host=server3.company.com ansible_connection=ssh ansible_user=root ansible_ssh_pass=Password123!
  # db servers
  db1 ansible_host=server4.company.com ansible_connection=winrm ansible_user=administrator ansible_password=Password123!

  # -- groups --
  # all web servers
  [web_servers] 
  web1
  web2
  web3
  # all db servers
  [db_servers] 
  db1
  # all servers (using web and db server groups to make a new group)
  [all_servers:children] 
  web_servers
  db_servers

Testing 🧪

refer to this link to get up and running

inventory.txt containing two groups and four targets.

[group1]
inventory_target_1 ansible_connection=community.docker.docker
inventory_target_2 ansible_connection=community.docker.docker

[group2]
inventory_target_3 ansible_connection=community.docker.docker
inventory_target_4 ansible_connection=community.docker.docker

ping all the inventory targets

ansible -m ping all -i inventory.txt

output

inventory_target_3 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}
inventory_target_2 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}
inventory_target_1 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}
inventory_target_4 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}

ping group1 inventory targets

ansible -m ping group1 -i inventory.txt