## Ansible
Ansible is used for automation.

In this post we will learn some basic stuff and workarounds in ansible.

Here is a sample ansible playbook:

```
hosts: localhost
vars_files:
  - ./vars/main.yml
tasks:
  - name: This a task
    vars:
      a: "apple"
      b: ["book", "cat", "dog"]
    command: echo "{{ a }}"
    register: sample_task
  - debug: var=sample_task # or msg="{{ sample_task }}"
```

#### Basic Commands:

##### hosts
---
This command contains a list or a environment where all the tasks will run. Hosts can be defined in multiple ways. Like using a custom inventory file, using default inventory file and directly writing after hosts module.
- Directly Writing after hosts module
`hosts: localhost`
- using inventory file
Create an inventory file with name `inventory` with following containts:
```
[host1]
IP_1
[host2]
IP_2
[host3]
IP_3
[host_list:children]
host1
host2
host3
```
Write hosts module as:
`hosts: host1:host2:host3` or `hosts: host1` or `hosts: hostlist`

To exucute playbook use command: `ansible-playbook -i inventory my_playbook.yml --private-key="KEY"`
- using default inventory
 Default inventory file is at `/etc/ansible/hosts`. If inventory file is not provided, this is used as inventory.

##### tasks
---
This command is used to write tasks to be executed on the environmet, all tasks will be inside this only, for that environment. A simple task is written as:
```
- name: This a task
  vars:
    a: "apple"
    b: ["book", "cat", "dog"]
  command: echo "{{ a }}"
  register: sample_task
```

##### script
---
Script module is used to upload script at the environment and execute the script. script will contain a complete playbook.
A sample task with script module:
```
- script: './files/my_script.yml -i inventory --private-key=keys/KEY.pem'
  args:
    chdir: '/home/ubuntu/scripts' # the inventory file and keys folder will be located here
  register: output
```

##### vars_files
---
List of files that contains the varibales needed in the tasks. A typical vars file:
```
INT_VAR: 12313
STR_VAR: "Apple"
```
use:
```
vars_files:
  - ./vars/main.yml
```

##### vars
---
This module is used to inialize new variable.

##### set_fact
---
This module is used to inialize new variable.

##### lineinfile
---

##### with_items, with_list, with_dict
---
For Itrating over list etc.
#### Data Structure in Ansible:
##### List:
---
```
vars:
  my_list:
    - 1
    - 2
    - 3
```
To append more:
```
vars:
  my_list: []
set_fact:
  my_list: "{{ my_list }} + [ {{ item }} ]"
```
##### Dictonary:
---
```
vars:
  dict:
    a: "apple"
    b: "book"
    c: "cat"
```
To append more:
```
- name: Create and add items to dict
  vars:
    def_val: "asdf"
    dict: {}
  set_fact:
    dict: '{{ dict | combine( { item: def_val } ) }}'
  with_items:
    - 1
    - 2
    - 3
```
To get values:
```
- name: Get values
  debug:
    msg: "{{item.key}}: {{ item.value }}"
  with_dict: "{{ dict }}"

```