压箱底的Ansible使用小技巧

var code = "ee730933-4cef-4440-95ca-b44eee8b2b9e"

配置

可以在当前项目目录下或者 /etc/ansible 目录下创建一个 ansible.cfg，配置如下：

[defaults]
# 设置fact的收集方式及过期时间
# gathering = batch
# fact_caching_timeout = 86400

# 指定fact缓存的实现方式并加速其收集速度
# fact_caching = jsonfile
# fact_caching_connection = /tmp/ansible_fact_cache

# 开启日志
# log_path=/path/to/logfile

# 如果你对每个任务的执行时长有兴趣，可以开启下面的开关
# callback_whitelist = profile_tasks

# 默认的json输出可读性不如这个，这个是强烈推荐的配置
stdout_callback = debug

# 同时并发执行的host个数，默认是3
# forks = 30

FAQ

如何在本地执行任务

有时你可能需要在本地执行某个特定任务（比如任务调试或者不希望到处安装依赖包时）可以使用delegate_to语句：

- name: install pymysql to use mysql_db module
  pip: pymysql
  delegate_to: localhost
- name: create a new database with name "test"
  mysql_db:
    database: demo
    state: present
  delegate_to: localhost

当变量未赋值时给出提示

可以使用vars_prompt, 比如:

---
- name: test_prompt_variable
  hosts: localhost
  vars_prompt:
    - name: build_number
      prompt: input the build number
      private: no
      when: build_number is not defined
      default: 1.1.0
  roles:
    - database

使用SSH KEY的方式登录主机以避免在每次登录时输入密码

# 使用ssh-keygen的生成一对密钥对，密钥文件通常保存在～/.ssh/目录下以id_rsa和id_rsa.pub命名，带pub后缀的时公钥
ssh-keygen
# 使用如下方式将公钥添加到远程主机的authorized_keys文件中
ssh-copy-id -i ~/.ssh/mykey user@host -p port

使用命令行执行特定模块

# syntax
ansible <pattern-of-hosts> -i [hosts-file] -e <environment setting> -m <module> -a <arguments of module>
# e.g.
ansible web -i myhosts -e '{"ansible_port":12345, "ansible_user":"myuser"}' -m shell -a "pwd"

务必掌握的几个常见模块

文件相关

fetch：从host下载文件到本地

例子：

- name: Storing in a path relative to the playbook
  fetch:
    src: /tmp/uniquefile
    dest: special/prefix-{{ inventory_hostname }}
    flat: yes

copy：从本地拷贝文件到host

例子：

- name: Copy file with owner and permission, using symbolic representation
  copy:
    src: /srv/myfiles/foo.conf
    dest: /etc/foo.conf
    owner: foo
    group: foo
    mode: u=rw,g=r,o=r

template：讲本地的模板文件拷贝到host

例子：

- name: Copy a version of named.conf that is dependent on the OS. setype obtained by doing ls -Z /etc/named.conf on original file
  template:
    src: named.conf_{{ ansible_os_family}}.j2
    dest: /etc/named.conf
    group: named
    setype: named_conf_t
    mode: 0640

执行

script：执行脚本文件

- name: Run a script using an executable in a system path
  script: /some/local/script.py
  args:
    executable: python3

command：执行特定命令

- name: Change the working directory to somedir/ and run the command as db_owner if /path/to/database does not exist.
  command: /usr/bin/make_database.sh db_user db_name
  become: yes
  become_user: db_owner
  args:
    chdir: somedir/
    creates: /path/to/database

shell：执行特定shell命令

- name: This command will change the working directory to somedir/
  ansible.builtin.shell:
    cmd: ls -l | grep log
    chdir: somedir/

shell和command模块很多时候可以互换，区别在于：command模块更加安全且高效，是官方推崇的方式，但是不支持shell特有的诸如管道的语法。

推荐读物

• Ansible: Up and running, 2nd Edition

• Ansible官方教程