ansible uses characters to simplify playbooks

Simplify playbooks with characters

Ansible roles have the following advantages:
1. Roles can group content and are easy to reuse
2. Roles can be used to define basic system information: web servers, database servers, etc.
3. Roles can make large projects easy to manage
4. Roles can be parallelized by different people Development

The following subdirectories should be included under the role directory:

ansible	Roles will separate playbooks with different functions. A standard role contains the following subdirectories:
defaults	The main.yml contains the default value of the role variable #The lowest priority among all variables
files	Contains static files referenced by role tasks
handlers	Mainly define handlers
meta	Role-related information, such as author, license, etc.
tasks	Define tasks
templates	The jinja2 template referenced by the task
tests	Can contain a manifest and test.yml playbook for testing
whose	Variables defining roles

## Use ansible characters in playbook
like:

- hosts: www.example.com
  roles:
    - role1
    - role2
      var1:var1
      var2:var2        为 role2 定义了两个变量，任何 defaults 和 vars 中的变量都会被覆盖

Reuse content with system roles

## Install System Role

 yum install -y rhel-system-roles

#The installed roles are located at:

 ls -l /usr/share/ansible/roles

#The content (view network role)

 ls -l /usr/share/ansible/roles/rhel-system-roles.network

## time synchronization role example
# See which roles can be used in the system

ansible-galaxy list

#Create directory to save variables

 mkdir -pv group_vars/all

#View help

 cat /usr/share/doc/rhel-system-roles/timesync/README.md

#Time zone setting example

 ansible-doc timezone | grep -A 4 "EXAMPLES"

# Manifest and configuration files

# modify the main playbook

vim configure_time.yml

---
- name: Time Sync
  hosts: groups
  roles:
    - rhel-system-roles.timesync
  post_tasks:
    - name: Set Timezone
      timezone:
        name: "{{ host_timezone }}"
      notify: restart crond
  handlers:
    - name: restart crond
      service:
        name: crond
        state: restarted

#Create a variable directory for the host group

 mkdir -pv group_vars/{group1,group2}

#Create time yml file and write

# Detect and run

ansible-playbook --syntax-check configure_time.yml
 ansible-playbook configure_time.yml

Creating a Role

You can search and download related roles on galaxy.ansible.com.

## Role creation process: divided into three steps
1. Create a role directory structure
2. Define the role content
3. Use the role in the playbook

## Create a character framework

[root@workstation mnt] cd project/
[root@workstation project] mkdir roles
[root@workstation project] cd roles/
[root@workstation roles] ansible-galaxy init my_role     创建目录，自动生成配置文件

 tree my_role

my_role #The specific role project name, such as nginx, tomcat, php (free setting)
├── defaults #Used to set default variables for the current role, this directory should contain a main.yml
file│ └── main.yml # main.yml, similar to the main function in the code, for unified management
├── files # used to store files called by the copy module or script module
├── handlers # used to define the actions performed when the condition is triggered in this role , This directory should contain a main.yml file
│ └── main.yml
├── meta # used to define the special settings of this role and its dependencies, this directory should contain a main.yml file
│ └── main .yml ├──
README.md #Description
file├── tasks #Used to define the task list of the current role, this directory should contain a main.yml
file│ └──
main.yml ├── templates #Used to store jinjia2 Templates, the template module will automatically find jinjia2 template files in this directory
├── tests #Used to store the role of the test role itself The playbook and host definition files are compared in the development and testing stage
│ ├── inventory is commonly used, this directory should contain a main.yml file and its own resource setting inventory
│ └── test.yml
└── vars #Used to define the variables used by this role, this directory should contain a main.yml file
└── main.yml

#Create and initialize

[root@workstation ~] mkdir role-create
[root@workstation ~] cd role-create/
[root@workstation role-create] mkdir -v roles;cd roles
mkdir: created directory 'roles'
[root@workstation roles] ansible-galaxy init myvhost
- myvhost was created successfully

Configure tasks
vim tasks / main.yml
'install, start and configure virtual host'

---
# tasks file for myvhost
- name: Install httpd
  yum:
    name: httpd
    state: latest
- name: Start and Enabled httpd
  service:
    name: httpd
    state: started
    enabled: true
- name: Install vhost file
  template:
    src: vhost.conf.j2
    dest: /etc/httpd/conf.d/vhost.conf
    owner: root
    group: root
    mode: 0644
  notify:
    - restart httpd

#Write handler [root @ workstation handlers] # vim main.yml

--
# handlers file for myvhost
- name: restart httpd
  service:
    name: httpd
    state: restarted

#Write html file

mkdir -p role-create/files/html      
vim files/html/index.html      创建index文件。 

Create a new files directory and create an html directory in it. Note that this is not the files directory in myvhost. You can put it anywhere. This is just for convenience.

#Configuration template

 vim templates/vhost.conf.j2

<VirtualHost *:80>
        DocumentRoot /www
        ServerName www.westos.org
</VirtualHost>

<VirtualHost *:80>
        DocumentRoot /bbs
        ServerName bbs.westos.org
</VirtualHost>

#Write playbook using roles [root @ workstation role-create] # vim use_vhost_role.yml

- name: use myvhost
  hosts: webservers
  pre_tasks:
    - name: pre_tasks message
      debug:
        msg: 'Ensure web server configuration'
  roles:
    - myvhost
  post_tasks:
    - name: Configure html
      copy:
        src: files/html/
        dest: "/var/www/vhosts/{{ ansible_hostname }}"
    - name: post_tasks message
      debug:
        msg: "Web server is configured."

'The host list used here is the system default: / etc / ansible / hosts'
execution result:



## Control the execution order
Sometimes it is necessary to perform some tasks before or after the role:
Keyword:
Before:
after pre_tasks: post_tasks