infra:ansible:inventory

About

inventory is a file that define the following entity:

the hosts
the group of host
the child relationship between group
and variables (connection variable,…). The preferred practice in Ansible is to not store variables in the main inventory file but in the group variable file and/or host variable file

You can use multiple inventory files at the same time when running a playbook

Format

The inventory file can be in one of many formats.

ini

The format for the default file /etc/ansible/hosts is an INI-like where:

The headings in brackets are group names

; variable definition for all hosts
[all:vars]
ansible_connection=ssh
ansible_user=vagrant
ansible_ssh_pass=vagrant

; host definition with optional variable
[group]
hostname connection_variable=value

where:

the most variables defined are connection variables

Example:

webserver ansible_user=manager ansible_become=yes
; When knowing only the IP
hostName1 ansible_host=192.0.2.50
; With another port 
hostName2 ansible_port=5555 


[webservers]
foo.example.com
bar.example.com

[dbservers]
one.example.com
two.example.com
three.example.com

Yaml

A YAML version would look like:

all:
  hosts:
    mail.example.com:
  children:
    webservers:
      hosts:
        foo.example.com:
        bar.example.com:
    dbservers:
      hosts:
        one.example.com:
        two.example.com:
        three.example.com:

Management

List

ansible-inventory -vvvvvv -i ansible/hosts-install.yaml --list

Set up / Location

The defaults location is /etc/ansible/hosts

You can specify a inventory file:

in the ansible config file
using the -i <path> option on the command line.

Example:

ansible -i /path/to/inventory/file
ansible -i /path/to/inventory/script

Variable

See Accessing information about hosts

inventory_hostname is the name of the hostname (alias)
inventory_hostname_short - inventory_hostname without the domain
ansible_hostname is the hostname of the machine
hostvars - all host variables

{{ hostvars['alias']['ansible_facts']['fact_name'] }}
# Example
{{ hostvars['test.example.com']['ansible_facts']['distribution'] }}

Creation

Dynamic

pull inventory from dynamic or cloud sources or different formats (YAML, ini, etc) (since version 2.4) through inventory plugins.

dynamic_inventory Scripts can be seen at contrib/inventory

Check

Output the graph with ansible-inventory
Check the host:

ansible -i myhosts/<yourfile>  -m command -a "hostname -f" all

graph

ansible-inventory -vvv -i ansible/hosts-install.yml --graph

ansible-inventory 2.7.8
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/ansible/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/dist-packages/ansible
  executable location = /usr/bin/ansible-inventory
  python version = 2.7.12 (default, Nov 12 2018, 14:36:49) [GCC 5.4.0 20160609]
Using /etc/ansible/ansible.cfg as config file
/ansible/playbooks/ansible/hosts-install.yml did not meet host_list requirements, check plugin documentation if this is unexpected
Parsed /ansible/playbooks/ansible/hosts-install.yml inventory source with ini plugin
@all:
  |--@ungrouped:
  |  |--all:
  |  |--ansible_host=10.40.35.122
  |  |--ansible_user=ansible
  |  |--children:
  |  |--hosts:
  |  |--ins:
  |  |--install-host:

Configuration / Plugins

ansible-config dump | grep INVENTORY_ENABLED

INVENTORY_ENABLED(default) = ['host_list', 'script', 'yaml', 'ini', 'auto']

Support

inventory parsed as ini file

This is often because of a problem in the yaml file.

Try this one from the doc

all: # keys must be unique, i.e. only one 'hosts' per group
    hosts:
        test1:
        test2:
            host_var: value
    vars:
        group_all_var: value
    children:   # key order does not matter, indentation does
        other_group:
            children:
                group_x:
                    hosts:
                        test5   # Note that one machine will work without a colon
                #group_x:
                #    hosts:
                #        test5  # But this won't
                #        test7  #
                group_y:
                    hosts:
                        test6:  # So always use a colon
            vars:
                g2_var2: value3
            hosts:
                test4:
                    ansible_host: 127.0.0.1
        last_group:
            hosts:
                test1 # same host as above, additional group membership
            vars:
                group_last_var: value

And run:

ansible-inventory -vvvvvv -i ansible/hosts.yaml --list

Table of Contents

Ansible - Inventory