备注：以下下示例主机组均为pxg

####系统符合就安装apache###
---
  - name: Install Apache on CentOS 7
    hosts: pxg
    remote_user: root  # 使用root身份执行命令
    tasks:
     - name: Install Apache
       yum:
         name: httpd  # Apache软件包名称
         state: present  # 安装Apache
       when: ansible_os_family == 'RedHat'  # 仅对Red Hat/CentOS系统执行

     - name: Start Apache service
       service:
         name: httpd  # Apache服务名称
         state: started  # 启动Apache服务
       when: ansible_os_family == 'RedHat'  # 仅对Red Hat/CentOS系统执行
...

###变量存在与否在回显提示###
---
- name: Conditional Task Execution
  hosts: pxg
  remote_user: root  # 使用root身份执行命令
  vars: 
      user: peng
      home: /home/peng
  tasks:
    - name: Check if user is defined
      debug:
        msg: "user is defined"
      when: user is defined

    - name: Check if home is defined
      debug:
        msg: "home is defined"
      when: home is defined
...

####判断发行版本然后停止httpd服务###
---
- name: 停止httpd服务
  hosts: pxg
  remote_user: root  # 使用root身份执行命令

  tasks:
    - name: 获取发行版信息
      ansible.builtin.setup:
        filter: "ansible_distribution"
      register: dist_info      # register 关键字用于将任务执行的结果保存到一个变量(dist_info)中，然后可以使用这个变量的值在 playbook 中的其他地方进行处理。

    - name: 停止httpd服务（如果发行版是CentOS或Fedora）
      ansible.builtin.service:
        name: httpd
        state: stopped
      when: dist_info.ansible_facts.ansible_distribution in ['CentOS', 'Fedora']
...

####判断根分区大小####
---
- name: Check Root Partition Space and Stop vsftpd
  hosts: pxg
  remote_user: root  # 使用root身份执行命令

  tasks:
    - name: Get Root Partition Space
      shell: df -h / | awk 'NR==2 {print $4}'  # 获取根分区可用空间（以G为单位）
      register: root_partition_space

    - name: Stop vsftpd Service
      systemd:
        name: vsftpd
        state: stopped
      when: root_partition_space |int < 3  # 当可用空间小于3G时停止服务

  handlers:
    - name: Start vsftpd Service
      systemd:
        name: vsftpd
        state: started
...