Ansible inventory - Httqm's Docs

with an ad-hoc command

ansible -m debug -a 'msg={{group_names}}' myServer1,myServer2

with a playbook

create an executable playbook file

playbookFile=./showAnsibleGroups; cat << EOF > "$playbookFile" && chmod +x "$playbookFile"
#!/usr/bin/env ansible-playbook

- hosts: all
  gather_facts: no
  tasks:
  - name: show the groups the host(s) are in
    debug:
      msg: "{{group_names}}"
EOF

run it :

./showAnsibleGroups -i inventories/ -l myServer1,myServer2

TASK [show the groups the host(s) are in] ***********************************************************************
ok: [myServer1] => {
    "msg": [
        "RHEL",
        "RHEL8",
        "preprod"
    ]
}


PLAY RECAP ******************************************************************************************************
myServer1	: ok=1	changed=0	unreachable=0	failed=0	skipped=0	rescued=0	ignored=0
myServer2	: ok=1	changed=0	unreachable=0	failed=0	skipped=0	rescued=0	ignored=0

short answer : you can't
long answer : you _could_ but that would be hacky and hard to maintain, so that's actually discouraged
longer answer : the good news is you don't even have to, read below !

How to proceed :

create several inventory files matching your needs :
[project root]

inventories/ the inventory files directory

hosts an inventory file

other_hosts another inventory file

more_hosts one more inventory file
This works both with
- ini-style
- yaml-style
Ansible inventories.
that's it, you can address :
- all hosts from all inventory files :
  <ansible command> -i inventories/ all
  -i inventories/ is equivalent to calling each inventory file with a distinct -i inventoryFile
- all hosts from specific inventory files :
  <ansible command> -i inventories/hosts -i inventories/other_hosts all
- hosts from a specific group :
  <ansible command> -i inventories/hosts -i inventories/other_hosts myGroup
feel free to test your targeting with ansible-inventory

you have setup a clean inventory with groups and groups of groups
you know how to target specific hosts : a list, a group, several groups, intersection of groups,
now the questions are :
- How can I check the actual list of hosts resulting from my inventory expression ? The easy solution would be to run
  - ansible with a dummy action, such as invoking the ping module
  - ansible-playbook , in --check mode
- which leads to another question : Is it even possible from a workstation that has no access to the managed hosts ?

ansible-inventory to the rescue !!!

ansible-inventory -i inventories myGroup --graph

This works fine unless you want to target hosts using group-based expressions (union, intersection, ). Read below

using the --list-hosts flags (docs.ansible.com (ansible), docs.ansible.com (ansible-playbook))

Let's consider the following Ansible inventory (just download it and cd into the download directory to use it). It's possible to select targets using various expressions :

everybody :
- ansible -i Ansible_inventory_example.ini everybody --list-hosts
- ansible -i Ansible_inventory_example.ini all --list-hoststhe all group is implicit
members of a single group :
- ansible -i Ansible_inventory_example.ini woman --list-hosts
- ansible -i Ansible_inventory_example.ini man --list-hosts
members of several groups (logical OR, union) :
- ansible -i Ansible_inventory_example.ini 'woman:man' --list-hosts
- expressions must be quoted to prevent special characters & and ! to be interpreted by the shell
members of both groups (logical AND, intersection) :
- ansible -i Ansible_inventory_example.ini 'woman:&man' --list-hosts
- ansible -i Ansible_inventory_example.ini 'man:&woman' --list-hosts
intersection of several groups (logical AND) :
ansible -i Ansible_inventory_example.ini 'woman:&wearsRed:&canFly' --list-hosts
as above, with more complex logical conditions (details) :
- women who can't fly :
  ansible -i Ansible_inventory_example.ini 'woman:!canFly' --list-hosts
- women who can fly, without being superheroes :
  ansible -i Ansible_inventory_example.ini 'woman:&canFly:!superhero' --list-hosts
- male superheroes who can fly but without blue on their suit :
  ansible -i Ansible_inventory_example.ini 'man:&superhero:&canFly:!wearsBlue' --list-hosts

The inventory file :

is the list of hosts that are controlled by Ansible (aka slaves).
lists hosts organized in groups (plus the default group all that has everybody).
can either be static (read below) or dynamic.
defaults to /etc/ansible/hosts. An alternate inventory file can be specified on the command line with -i alternateInventoryFile
can either be in YAML or in INI format :
```
[groupSlaves]						group name
slave1	ansible_host=192.168.105.114		details
slave2	ansible_host=192.168.105.80

[myGroup1]						group name
slave1

[myGroup2]						group name
slave2
```
- This syntax is strongly related to patterns, the way to declare targets of our actions.
- It is possible to declare groups of groups with children :
  - :children for an inventory in INI format
  - children: for an inventory in YAML format

Default groups

The implicit group all includes all slaves.
There is also another group named ungrouped. The logic behind Ansible is that all slaves must belong to at least 2 groups : all and "an other one". If there is no such "other one", ungrouped will be that one.

Both groups will always exist and don't need to be explicitly declared.

Ansible inventory - List and organize the managed hosts

How to list the group(s) a host belongs to ?

with an ad-hoc command

with a playbook

Can an inventory file `include` another inventory file ?

How to proceed :

How to proof inventory expressions ?

Situation

Solution

ansible-inventory to the rescue !!!

using the --list-hosts flags (docs.ansible.com (ansible), docs.ansible.com (ansible-playbook))

The inventory file

Default groups

How to list the group(s) a host belongs to ?

with an ad-hoc command

with a playbook

Can an inventory file include another inventory file ?

How to proceed :

How to proof inventory expressions ?

Situation

Solution

ansible-inventory to the rescue !!!

using the --list-hosts flags (docs.ansible.com (ansible), docs.ansible.com (ansible-playbook))

The inventory file

Default groups

Can an inventory file `include` another inventory file ?