Asible

Determine the version of Ansible that is installed:

$ ansible --version

The output will give you location of cfg as config file = /home/user100/.ansible.cfg. That file will give you location of inventory and you can check that file as follow:

 $ cat /home/user100/.ansible.cfg
 ...
 inventory = /home/user100/my_inventory/inventory.txt
 ...

$ cat /home/user100/my_inventory/inventory.txt
ansible_user=user1
ansible_ssh_pass=s3cret
ansible_port=22

[web]
node1 ansible_host=x.x.x.x
node2 ansible_host=x.x.x.x
node3 ansible_host=x.x.x.x

[control]
ansible ansible_host=x.x.x.x

Ad Hoc Commands

• list all hosts in inventory > $ ansible all --list-hosts
• ping all hosts in web group > $ ansible web -m ping
• get uptime from hosts in web group > ansible web -m command -a "uptime" -o
• get uptime from specific host only > ansible node1 -m command -a "uptime" -o
• install apache with yum on all hosts in web group > $ ansible web -m yum -a "name=httpd state=present" -b -o
• start apache on all hosts in web group > $ ansible web -m service -a "name=httpd state=started" -b

Playbook
install_apache.yaml

---
- name: Install the apache web service
  hosts: web
  become: yes

  tasks:
   - name: install apache
     yum:
       name: httpd
       state: present

   - name: start httpd
     service:
       name: httpd
       state: started

Tasks
Task run sequentially

Module	Description
file	Create directory
yum	Install packages
service	Start/Stop services
template	Render template file from template
get_url	Fetch file from url
git	clone git from a repo

Hnadlers
if task has notify: handler_name then handlers are called after task completion, e.g.:

tasks:
- name: " package is present"
  yum:
    name: ""
    state: latest
  notify: restart webserver 

- name: latest index.html file is present
  copy:
    src: files/index.html
    dest: /var/www/html/

handlers:
- name: restart webserver 
  service:
    name: ""
    state: restarted

Variables
Variables with same name defined in multiple sources are overwritten in specific order:

1. Extra vars
2. Task vars (only for task)
3. Block vars (only for tasks in block)
4. Role and include vars
5. Play vars_files
6. Play vars_prompt
7. Play vars
8. set_facts
9. Registered vars
10. Host facts
11. Playbook host_vars
12. Playbook group_vars
13. Inventory host_vars
14. Inventory group_vars
15. Inventory vars
16. Role defaults

Roles
Packaging of closely related ansible content in a directory structure to be shared easily.

Ansible galaxy Online hub for finding, reusing and sharing ansible roles.
# ansible-galaxy init role-name

Ansible
Inventory
Playbook
Module