Ansible playbook小記

上一次寫完 Ansible 簡單的指令測試

今天來介紹 playbook

playbook  簡單來說就是

• 把要執行的 ansible 指令還有可能遠端主機會使用到的檔案都集中到一個目錄內.
• 以YAML 語法來寫
• 以 ansible-playbook 指令執行
• playbook 裡面會有不同的 play ( 可以把看成要執行的script )
• 每個 play 必須有
• 要執行的 host ( 對應我們設定的 hosts 或是 inventory 檔案 )
• task ( 執行那些工作)

以下是看書上,自己的整理筆記

playbook

• A script is called a playbook.
• A playbook describes which hosts( what Ansible calls remote servers ) to configure, and an ordered list of tasks to perform on those hosts.
• Ansible runs each task in parallel across all hosts.
• Ansible waits until all hosts have completed a task before moving to the next task.
• Ansible runs the tasks in the order that you specify them.
• 使用 ansible-playbook 指令來執行
• # 例如 ansible-playbook  web-notls.yml
• 如果檔案本身可以被執行
• 也可以在檔案第一行加上
• #!/usr/bin/env  ansible-playbook
• 來直接執行
• Ansible playbooks written in YAML syntax.
• YAML
• Yet Another Markup Language
• http://yaml.org/
• https://zh.wikipedia.org/wiki/YAML
• Start of File
• 以 3 個 --- 開始
• 不加上去也可以
• 註解
• 以 # 來進行單行註解
• #就是註解開始
• Strings
• 不一定要加上引號
• 可是有的時候為了易讀性, 可以使用 單引號或是雙引號
• Booleans
• 使用 True 或是 Yes 都可以視為真
• 但是還是用 True 不會混亂
• Lists

They are delimited with hyphens, like this:

- My Fair Lady

- Oklahoma

- The pirates of Penzance

# inline 格式list

[My Fair Lady, Oklahoma, The Pirates of Penzance]

• Dictionaries

They look like this:

address: 742 Evergreen Terrace

city: Springfield

state: North Takoma

# inline  格式

{address: 742 Evergreen Terrace, city: Springfield, state: North Takoma}

• Line Folding

# 使用 > 符號來進行 單行摺疊, 有點類似 shell script 放在行尾的 \

# 目的在於讓一個很長的單行, 有效率地被呈現

address: >

     Department of Computer Science,

     A.V. Williams Building,

     University of Maryland

city: College Park

state: Maryland

# address 那邊就可以看成一行

• A playbook is a list of plays
• Plays
• Every play must contain:
• * A set of hosts to configure
• * A list of tasks to be executed on those hosts
• Three common optional settings are
• name
• A comment that describes what the play is about.
• Ansible will print this out when the play starts to run.
• sudo
• If true, Ansible will run every task by sudo.
• vars
• A list of variables and values.
• 在 play 內用  {{  }} 來使用 variables
• Other optional settings are
• Handlers

A handler is similar to a task, but it runs only if it has been notified by a task.

A task will fire the notification if Ansible recognizes that the task has changed the state of the system.

# 當 task 改變系統狀態時, 會進行 notify 的動作

tasks:

 - name: copy TLS key

    copy: src=files/nginx.key dest={{ key_file }} owner=root mode=0600

    notify: restart nginx

# handlers 可能有很多個, notify 會去比對 handlers 的名稱, 如果符合就進行該模組

handlers:

- name: restart nginx

  service: name=nginx state=restarted

# 也就是說, 只有真的系統產生改變的時候, 例如 TLS key 被換掉, 才會重新啟動 nginx

• Handlers only run after all of the tasks are run, and the only run once, even they are notified multiple times.
• # Handlers 在所有tasks執行完才執行, 不管被呼叫多少次, 都只執行一次.
• hosts
• default: /etc/ansible/hosts
• Tasks
• Something to be executed on hosts
• Use different modules to do different task.
• Modules
• Modules are scripts that come packaged with Ansible and perform some kind of action on a host.
• http://docs.ansible.com/ansible/modules_by_category.html