【自动化运维神器Ansible】Ansible常用模块之replace模块详解

• 在Ansible中，与文件内容修改相关的模块还有lineinfile和blockinfile，它们的主要区别如下：

- name: Replace text in file
  ansible.builtin.replace:
    path: /path/to/file       # 目标文件路径
    regexp: 'search_pattern'  # 要匹配的正则表达式
    replace: 'replacement'    # 替换后的内容

- name: Advanced replace example
  ansible.builtin.replace:
    path: /etc/nginx/nginx.conf
    regexp: '^worker_processes\s+\d+;'
    replace: 'worker_processes 4;'
    backup: yes               # 修改前创建备份文件
    validate: 'nginx -t -c %s' # 修改后验证文件有效性
    after: '^# worker_processes' # 只在特定内容之后进行替换
    before: '^# end of config'   # 只在特定内容之前进行替换

• 场景：修改SSH配置文件，将PermitRootLogin设置为no

- name: Disable root login via SSH
  ansible.builtin.replace:
    path: /etc/ssh/sshd_config
    regexp: '^#?PermitRootLogin.*'
    replace: 'PermitRootLogin no'
    backup: yes

• 场景：交换配置文件中的键值顺序

- name: Swap key-value pairs
  ansible.builtin.replace:
    path: /etc/someapp/config.conf
    regexp: '^(\w+)\s*=\s*(\w+)$'
    replace: '\1 = new_\2'

• 场景：同时修改多个配置项

- name: Update multiple configurations
  ansible.builtin.replace:
    path: /etc/redis/redis.conf
    regexp: '^(timeout|tcp-keepalive)\s+\d+'
    replace: '\1 300'

• 场景：只在特定配置段内进行替换

- name: Replace only in specific section
  ansible.builtin.replace:
    path: /etc/php/php.ini
    regexp: '^memory_limit = .*'
    replace: 'memory_limit = 256M'
    after: '^\[PHP\]'
    before: '^\[.*\]'

• 文件检查：首先检查目标文件是否存在，不存在则任务失败
• 内容读取：读取文件内容到内存中
• 正则匹配：应用正则表达式进行匹配
• 替换判断：如果没有匹配内容，则跳过修改；否则执行替换
• 备份处理：根据backup参数决定是否创建备份
• 文件修改：将修改后的内容写入文件
• 验证处理：如果有验证命令，则执行验证，验证失败则恢复备份
• 任务完成：最终返回任务执行结果

• 始终备份：在生产环境中使用backup: yes参数
• 验证修改：对于关键配置文件，使用validate参数
• 测试正则：先在测试环境验证正则表达式的准确性

• 批量操作：尽量一次替换多个相关配置，减少文件I/O
• 精确匹配：编写精确的正则表达式，避免不必要的匹配
• 限定范围：使用after/before限定替换范围

• 场景：多行模式替换

- name: Replace multi-line block
  ansible.builtin.replace:
    path: /etc/nginx/nginx.conf
    regexp: |
      server \{
        listen 80;
        server_name old.example.com;
      \}
    replace: |
      server {
        listen 80;
        server_name new.example.com;
      }

- name: Handle special characters
  ansible.builtin.replace:
    path: /path/to/file
    regexp: '^JAVA_OPTS=.*'
    replace: 'JAVA_OPTS={{ some_var | regex_escape }}'

- name: Update Java memory settings
  hosts: java_servers
  tasks:
    - name: Set JVM heap size
      ansible.builtin.replace:
        path: /opt/app/bin/startup.sh
        regexp: '-Xmx\d+m'
        replace: '-Xmx2048m'
        validate: '/opt/app/bin/check_config.sh %s'

- name: Standardize timezone configuration
  hosts: all
  tasks:
    - name: Ensure correct timezone in /etc/timezone
      ansible.builtin.replace:
        path: /etc/timezone
        regexp: '^.*$'
        replace: 'Asia/Shanghai'

- name: Update load balancer backend servers
  hosts: load_balancers
  vars:
    backend_servers: "{% for host in groups['web_servers'] %}{{ hostvars[host].ansible_default_ipv4.address }}:8080;{% endfor %}"
  tasks:
    - name: Update nginx upstream configuration
      ansible.builtin.replace:
        path: /etc/nginx/conf.d/upstream.conf
        regexp: 'server .*; # auto-generated'
        replace: '{{ backend_servers }} # auto-generated'
        validate: 'nginx -t -c /etc/nginx/nginx.conf'

- name: Dynamic replacement using Jinja2
  ansible.builtin.replace:
    path: /etc/application/config.ini
    regexp: '^max_connections = \d+'
    replace: 'max_connections = {{ max_connections | default(100) }}'

- name: Replace with content from another file
  ansible.builtin.replace:
    path: /etc/motd
    regexp: '^Welcome message:.*'
    replace: 'Welcome message: {{ lookup("file", "/opt/messages/welcome.txt") }}'

- name: Conditional replacement
  ansible.builtin.replace:
    path: /etc/daemon.conf
    regexp: '^log_level = .*'
    replace: 'log_level = {{ "debug" if debug_mode else "info" }}'
  when: "'config_server' in group_names"