An overview of Roles

Roles can automatically load variable files, task s, handlers, and so on, depending on the hierarchy.
Simply put, Roles is about including variables, files, tasks, modules, and processors in separate directories and easily.
Roles is typically used in scenarios where services are built on hosts, but it can also be used in scenarios such as building daemons.

Directory of Roles

Steps to use Roles in playbook

• Create a directory with roles command

#yum is ready by default
mkdir /etc/ansible/roles/ -p 

• Create global variable directory

mkdir /etc/ansible/group_vars/ -p
touch /etc/ansible/group_vars/all
#File name defined by itself, note when referencing

• Create directories in the roles directory with commands by role name, such as httpd

mkdir /etc/ansible/roles/common -p

• Create files, handlers, tasks, templates, meta, defaults, and vars directories in the directory of each role command. Unused directories can be created as empty directories, but not without creating them

mkdir /etc/ansible/roles/httpd/{files,templates,tasks,handlers,vars,defaults,meta} -p
mkdir /etc/ansible/roles/mysql/{files,templates,tasks,handlers,vars,defaults,meta} -p

• Create a main.yml file in the handlers, tasks, meta, defaults, vars directory for each role, and never customize it

touch /etc/ansible/roles/httpd/{defaults,vars,tasks,meta,handlers}/main.yml
touch /etc/ansible/roles/mysql/{defaults,vars,tasks,meta,handlers}/main.yml

• In the playbook file, invoke roles

vim /etc/ansible/site.yml

- hosts: webserver
  remote_user: root
  roles:
     - httpd
     - mysql

Installation and Setup of LAMP Architecture Instance Demo

• Create Service Component Working Directory

mkdir /etc/ansible/roles/httpd/{files,templates,tasks,handlers,vars,defaults,meta} -p
mkdir /etc/ansible/roles/mysql/{files,templates,tasks,handlers,vars,defaults,meta} -p
mkdir /etc/ansible/roles/php/{files,templates,tasks,handlers,vars,defaults,meta} -p

• Create an empty yml file

touch /etc/ansible/roles/httpd/{defaults,vars,tasks,meta,handlers}/main.yml
touch /etc/ansible/roles/mysql/{defaults,vars,tasks,meta,handlers}/main.yml
touch /etc/ansible/roles/php/{defaults,vars,tasks,meta,handlers}/main.yml

• Writing httpd modules

#Write a simple tasks/main.yml
vim /etc/ansible/roles/httpd/tasks/main.yml

- name: ensure apache is at the latest version 
  yum: pkg={{ pkg }} state=latest

#Define variables, either in global variables or roles role variables, generally in role variables
vim /etc/ansible/roles/httpd/vars/main.yml

pkg: httpd

• Writing mysql module

vim /etc/ansible/roles/mysql/tasks/main.yml

- name: ensure mysql is at the latest version 
  yum: pkg={{ pkg }} state=latest

#Define Variables
vim /etc/ansible/roles/mysql/vars/main.yml

pkg: mariadb*

• Writing php modules

vim /etc/ansible/roles/php/tasks/main.yml

- name: ensure php is at the latest version
  yum: pkg={{ pkg }} state=latest

#Define Variables
vim /etc/ansible/roles/php/vars/main.yml

pkg: php*

• Write roles instances

vim /etc/ansible/site.yml

- hosts: webserver
  remote_user: root
  roles:
   - httpd
   - mysql
   - php

#Execute the script
ansible-playbook site.yml 

On the remote host after execution, query to verify whether the specified service is installed

rpm -q httpd

httpd-2.4.6-90.el7.centos.x86_64

rpm -q mariadb

mariadb-5.5.64-1.el7.x86_64

rpm -q php

php-5.4.16-46.1.el7_7.x86_64

Thank you for reading!