Ansible - Inventory

/etc/ansible/hosts	default inventory location
-i	specify inventory

You can specify the location of your inventor file in your config file:

ansible.cfg
inventory=/opt/inv/hosts

Specify multiple inventory locations:

ansible-playbook test.yml -i /opt/inv/dev -i /opt/inv/prod

Basic Inventory Files

• Both INI and YAML formats can be used for Ansible inventory files.
• Host specific variables can be set in the config files.

Default groups:

• all - all hosts
• ungrouped - all hosts without a group

Here is an example of a INI formatted config file:

/etc/ansible/hosts


mail.example.com

[webservers]
foo.example.com
bar.example.com
www[01:50].example.com

[dbservers]
one.example.com
two.example.com
host1 http_port=80 maxRequestsPerChild=808
badwolf.example.com:5309   # custom ssh ports (openssh, not paramiko)
localhost              ansible_connection=local

Here is an example of a YAML formatted config file:

/etc/ansible/hosts


ungrouped:
  hosts:
    mail.example.com:
webservers:
  hosts:
    foo.example.com:
    bar.example.com:
dbservers:
  hosts:
    one.example.com:
    two.example.com:
    three.example.com:
    host1:
      http_port: 80
      maxRequestsPerChild: 808

Variables and Groups

• Sub groups can be created.
• Variables can be created on a group level.

INI format:

[web]
host1
host2

[web:vars]
port=8080
x=50

[db:children]
mysql
postgresql

[db:vars]
datadir="/data"
port=1234

[mysql]
test1
test2
[postgresql]
test3
test4

YAML format:

web:
  hosts:
    host1:
    host2:
  vars:
    port: 8080
    x: 50
db:
  children:
    mysql:
      test1:
      test2:
    postgresql:
      test3:
      test4:
  vars:
    datadir: "/data"
    port: 1234

Var Files

• Host and group variables can be defined in separate files.
• These files need to be in YAML format ( .yaml, .yml, .json )
• They are relative to the path of the inventory file
• Hosts and groups will have files or dirs named after them to contain their vars.

Group vars example paths:

/etc/ansible/group_vars/	dir for group variables
/etc/ansible/group_vars/all	all
/etc/ansible/group_vars/web.yaml	var file for web group
/etc/ansible/group_vars/db	dir for db group
/etc/ansible/group_vars/db/data.yaml	var file for db group
/etc/ansible/group_vars/db/control.yaml	var file for db group (another one)

Host var example paths:

/etc/ansible/host_vars/	dir for host variables
/etc/ansible/host_vars/host1.yaml	vars for host1
/etc/ansible/host_vars/host2.yaml	vars for host2
/etc/ansible/host_vars/test1/	dir for host test1
/etc/ansible/host_vars/test1/data1.yaml	file for host test1
/etc/ansible/host_vars/test1/data2.yaml	file for host test1

Dynamic Inventory

Using group_by for dynamic groups:

---

 - name: talk to all hosts just so we can learn about them
   hosts: all
   tasks:
     - name: Classify hosts depending on their OS distribution
       group_by:
         key: os_{{ ansible_facts['distribution'] }}

Now just on the CentOS hosts…

 - hosts: os_CentOS
   gather_facts: False
   tasks:
     - # tasks that only happen on CentOS go in this play

Variables file to include:

group_vars/os_CentOS.yml


---
asdf: 42