Ansible: Playbooks

What is YAML:

YAML stands for YAML Ain’t Markup Language, which is human-readable and often used in the configuration file.

Features of YAML:

• Compared to XML or JSON, YAML is less complex and provides the same features.

• It provides configuration settings without the need to learn complex code types such as CSS, JavaScript or PHP

Basic Rules for YAML:

•  You must end the YAML files with .yaml or .yml extension.

•  YAML must be case sensitive.

•  YAML doesn’t support the use of tabs. Instead of tabs, it uses spaces which are supported universally.

Basic Data Types of YAML:

YAML supports some basic data types which can be used with programming languages. Such as

1. Scalars: Strings or numbers.

2. Sequences: arrays or lists.

3. Mappings: hashes or dictionaries.

Example of Yaml file:
---
- hosts: dev
  become: true
  tasks:
  - name: to install httpd
    yum: 
    name: httpd 
    state: latest  - name: to install tomcat
    yum: name= tomcat state= latest  - name: to start httpd service
    service: name=httpd state=started  - name: to start tomcat service
    service: name=tomcat state=started

Playbooks:

1. Hosts and Users
2. Tasks lists
3. Handlers
4. Ansible Variables(Vars, Vars_prompt)
5. Ansible Loops

Hosts and Users:

Each play in a playbook, you get to choose which machines in your infrastructure to target and what remote user to complete steps(called tasks).

Ex:

---
- hosts: dev
  remote_user: root

Tasks List:

• Each playbook contains a list of tasks.

• Tasks are executed in order, one at a time, against all machines matched by the host pattern.

• The playbook will run from top to bottom.

Ex:

tasks:
- name: to install apache2
  apt:
  name: apache2
  state: latest

Handlers:

Running operations On Change.

Example:

---
- hosts: dev
  remote_user: true
  tasks:
  - name: install apache2
  apt:
  name: apache2
  state: latest
  notify:
  - start apache
  - name: to install tomcat  apt:
  name: tomcat7 
  state: latest
  notify:
  - start tomcat

handlers:
 - name: start apache
   service:
   name: apache2
   state: started - name: start tomcat
   service:
   name: tomcat7
   state: started

Ansible Variables:

• A Variable is an element which can hold a specific value.

• Variable names can be letters, numbers, and underscores.

• Variables should start with a letter.

• Here we have two types of variable methods, 1- Vars & 2- Vars_prompt

Vars:

Vars is nothing but a static functionality. Once the functions in playbooks are declared it can not change.

Example:
---
- hosts: all
  remote_user: root
  vars:
  pack1: net-tools
  pack2: wget
  tasks:
  - name: install package {{pack1}}
    yum:
    name:"{{pack1}}"
    state: latest
    when: ansible_distribution=="CentOS"

  - name: install package {{pack2}}
    apt:
    name: "{{Pack2}}"
    state: latest
    when: ansible_distribution=="Ubuntu"

Vars_prompt:

It will take the user input while executing playbook with vars_prompt and store into a variable.

Example: 
---
- hosts: centos
  remote_user: root
  vars_prompt:
  - name: pack_name
  prompt: Give Package name
  private: no
  tasks:
  - name: install package {{pack_name}}
    yum:
    name: "{{pack_name}}
    state: latest

Ansible Loops:

Ansible Loops can do many things in one task, such as create a lot of users, copy a set of files, install a lot of packages.

Example: copy multiple files using ansible loops.

---
- hosts: prod
  remote_user: root
  tasks: 
  - name: Copy{{item}}
  copy:
  src: /root/files/{{item}}
  dest: /tmp/{{item}}
  with_items:
  - abc1.txt
  - abc2.txt
  - abc3.txt

Add multiple users using ansible loops:

Example:
---
- hosts: all
  remote_user: root
  tasks: 
  - name: add group
    group:
    name:"sales"
    state: present

  - name: add user {{item}}
    usr:
    name: {{item}}
    group:"sales"
    state: "present"
    with_items:
    - user1
    - user2
    - user3

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