Variable used to lookup inventory value

Gonzalo Servat

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Nov 27, 2013, 7:48:33 PM11/27/13

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Hi All,

This might be more of a Jinja question, but I couldn't find an answer to this.

Say I have an inventory value that stores the main NIC name and I want to lookup the IP address for it from a fact. How can this be done in the one line? Non working example:

debug: msg="ip address is {{ ansible_{{ main_nic }}.ipv4.address }}"

GS

Michael DeHaan

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Nov 27, 2013, 7:52:03 PM11/27/13

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You can build variables dynamically through hostvars, which is a hash of all variables, host by host:

{{ hostvars[inventory_hostname]["ansible_" + main_nic].ipv4.address }}

inventory_hostname is the name of the current host in the host loop.

(Nesting templates in templates definitely will not work)

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Gonzalo Servat

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Nov 27, 2013, 7:54:05 PM11/27/13

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Perfect. That works. Again, thank you :)

GS

edroz...@gmail.com

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May 1, 2014, 1:25:48 PM5/1/14

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Hi Michael,

I tried using the {{ hostvars[inventory_hostname] trick but that variable

space does not include variables defined in a role such as "myrole/vars/main.yaml."

How can I programmatically reference variables defined within a role?

Thank you,

--Ed

Michael DeHaan

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May 1, 2014, 5:28:34 PM5/1/14

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I believe there was a ticket about hostvars not including *all* of the variables, which it should, that should now be resolved.

If you still see this in 1.6 let me know.

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Michael Hoglan

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Oct 15, 2014, 2:18:35 PM10/15/14

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Sorry to drag up an old thread, but this was one of the closer conversations out of the ones I found for what I was seeing.

Looking through old tickets, it looks like there used to be an issue when accessing hostvars[inventory_hostname] that you would not get all the vars associated with the host, such as ones added from add_host call. I see this does work, however, if I debug just the hostvars itself (not hostvars[inventory_hostname]) I don't get the same results.

The var does exist, and it can be used in plays, I mainly keep running into this as I am debugging and trying to see what vars exist for all hosts

Given a host file of:

[launched]
10.0.3.234 test_var=test
10.0.3.162 test_var=test

And a playbook of

---
- name: Playbook testing inventory var debugging
hosts: launched
user: root
gather_facts: yes
tasks:
- name: Output inventory var
debug: var=test_var
- name: Output inventory var from hostvars
debug: var=hostvars[inventory_hostname].test_var
- name: Output hostvars[inventory_hostname]
debug: var=hostvars[inventory_hostname]
- name: Output hostvars
debug: var=hostvars

The last debug for var=hostvars will not output the vars from the inventory file. The var exists, so this is kind of cosmetic, but it threw me off for a bit as I was working with add_host for dynamic EC2 provisioning and wasn't seeing the vars I was expecting when doing debug hostvars to look at all the vars for all hosts.

(ansible)[ec2-user@ip-10-0-0-226 playbooks]$ ansible-playbook -i launched test_inventory_var_debug.yml

PLAY [Playbook testing inventory var debugging] *******************************

GATHERING FACTS ***************************************************************
ok: [10.0.3.162]
ok: [10.0.3.234]

TASK: [Output inventory var] **************************************************
ok: [10.0.3.234] => {
"test_var": "test"
}
ok: [10.0.3.162] => {
"test_var": "test"
}

TASK: [Output inventory var from hostvars] ************************************
ok: [10.0.3.234] => {
"hostvars[inventory_hostname].test_var": "test"
}
ok: [10.0.3.162] => {
"hostvars[inventory_hostname].test_var": "test"
}

TASK: [Output hostvars[inventory_hostname]] ***********************************
ok: [10.0.3.234] => {
"hostvars[inventory_hostname]": {
"ansible_all_ipv4_addresses": [
"10.0.3.234"
],
...
"ansible_virtualization_type": "xen",
"group_names": [
"launched"
],
"inventory_hostname": "10.0.3.234",
"inventory_hostname_short": "10",
"module_setup": true,
"test_var": "test"
}
}
ok: [10.0.3.162] => {
"hostvars[inventory_hostname]": {
"ansible_all_ipv4_addresses": [
"10.0.3.162"
],
...
"ansible_virtualization_type": "xen",
"group_names": [
"launched"
],
"inventory_hostname": "10.0.3.162",
"inventory_hostname_short": "10",
"module_setup": true,
"test_var": "test"
}
}

TASK: [Output hostvars] *******************************************************
ok: [10.0.3.234] => {
"hostvars": {
"10.0.3.162": {
"ansible_all_ipv4_addresses": [
"10.0.3.162"
],
...
"ansible_virtualization_type": "xen",
"module_setup": true
}
}
}
ok: [10.0.3.162] => {
"hostvars": {
"10.0.3.162": {
"ansible_all_ipv4_addresses": [
"10.0.3.162"
],
...
"ansible_virtualization_type": "xen",
"module_setup": true
}
}
}

PLAY RECAP ********************************************************************
10.0.3.162 : ok=5 changed=0 unreachable=0 failed=0
10.0.3.234 : ok=5 changed=0 unreachable=0 failed=0

Anyways, let me know if I misunderstand this or if there is a different var to be looking at for the inventory vars. I can open an issue ticket also.