ansbile-playbook is a collection of system ansible commands, which is written in the yaml language and runs the process. The ansbile-playbook commands are executed in top-down order. At the same time, playbook has created many features. It allows you to transfer the status of a certain command to a subsequent command. For example, you can grab content from a file on one machine and attach it as a variable, and then use it on another machine. This allows you to implement some complex deployment mechanisms that are not possible with ansible commands.

Playbook is used through the ansible-playbook command. Its parameters are similar to the ansible command, such as the parameters -k (–ask-pass) and -K (–ask-sudo) to ask for the ssh password and sudo password, and -u to specify the user. ,These instructions can also be written in the playbook through ,prescribed units. Simple usage of ansible-playbook: ansible-playbook example-play.yml.

A simple ansible-playbook example is given below to understand its composition.

# cat user.yml
- name: create user
hosts: all
user: root
gather_facts: false
vars:
- user: "test"
tasks:
- name: create user
user: name="{{ user }}"

The function implemented by the playbook above is to add a new user:

The name parameter provides an overview of the functions implemented by the playbook. During subsequent execution, the value of the name variable will be printed;

The hosts parameter specifies which hosts to participate in;

The user parameter specifies the user to use to log in to the remote host;

The gather_facts parameter specifies whether to execute the setup module to obtain host-related information before the following tasks are executed. This will be used when subsequent tasks will use the information obtained by the setup;

The vars parameter specifies a variable. Here it refers to a user variable whose value is test. It should be noted that the variable value must be enclosed in quotation marks;

task specifies a task, and the name parameter below it is also a description of the task, which will be printed out during execution. User specifies calling the user module, name is a parameter in the user module, and the added user name calls the value of the user variable above. The specific execution results are as follows:

[root@361way playbooks]# ansible-playbook user.yml
PLAY [create user] ************************************************************
TASK: [create user ] **********************************************
changed: [10.212.52.252]
changed: [10.212.52.14]
changed: [10.212.52.16]
PLAY RECAP ********************************************************************
10.212.52.14 : ok=1 changed=1 unreachable=0 failed=0
10.212.52.16 : ok=1 changed=1 unreachable=0 failed=0
10.212.52.252 : ok=1 changed=1 unreachable=0 failed=0

Similarly, if you want to delete this newly added user, you only need to replace the last line of the playbook file with the following line and then execute the corresponding playbook:

user: name="{{ user }}" state=absent remove=yes

Give us a slightly more complicated example, using ansible-playbook to simultaneously patch bash shellcode vulnerabilities on N hosts. It should be noted that there may be different system versions distributed among the hosts on the existing network. It is assumed here that both centos5 and 6 versions exist on the existing network. The specific playbook content is as follows:

# cat update_bash.yml
- hosts: all
remote_user: root
gather_facts: True
tasks:
- name: update bash in redhat 6 version
yum: name=http://mirrors.aliyun.com/centos/6.6/os/x86_64/Packages/bash-4.1.2-29.el6.x86_64.rpm.rpm state=present
when: ansible_os_family == "RedHat" and ansible_distribution_version|int >=6
- name: update bash in redhat 5 version
yum: name=http://mirrors.hustunique.com/centos/5/updates/x86_64/RPMS/bash-3.2-33.el5.1.x86_64.rpm state=present
when: ansible_os_family == "RedHat" and ansible_distribution_version|int 
<p>The when statement is used above, and the gather_facts setup module is also enabled. The ansible_os_family variable and ansible_distribution_version variable here are the information obtained directly from the setup module. </p>
<p>If there are a large number of hosts, just add -f when running and select an appropriate number of concurrent hosts. I used this here and the bash upgrade was completed quickly. </p>
<div style="font-size: 14pt; color: white; background-color: black; border-left: red 10px solid; padding-left: 14px; margin-bottom: 20px; margin-top: 20px;"><strong>3. The composition of playbook</strong></div>
<p>playbook是由一個(gè)或多個(gè)“play”組成的列表。play的主要功能在于將事先歸并為一組的主機(jī)裝扮成事先通過ansible中的task定義好的角色。從根本上來講所謂task無非是調(diào)用ansible的一個(gè)module。將多個(gè)play組織在一個(gè)playbook中即可以讓它們聯(lián)同起來按事先編排的機(jī)制同唱一臺(tái)大戲。其主要有以下四部分構(gòu)成</p>
<ol class="linenums">
<li class="L0"><span class="pln">playbooks組成：</span></li>
<li class="L1"><span class="pln"> Target section： 定義將要執(zhí)行 playbook 的遠(yuǎn)程主機(jī)組</span></li>
<li class="L2"><span class="pln"> Variable section： 定義 playbook 運(yùn)行時(shí)需要使用的變量</span></li>
<li class="L3"><span class="pln"> Task section： 定義將要在遠(yuǎn)程主機(jī)上執(zhí)行的任務(wù)列表</span></li>
<li class="L4"><span class="pln"> Handler section： 定義 task 執(zhí)行完成以后需要調(diào)用的任務(wù)</span></li>
</ol>
<p>而其對(duì)應(yīng)的目錄層為五個(gè)，如下：</p>
<ol class="linenums">
<li class="L0"><span class="pln">一般所需的目錄層有：(視情況可變化)</span></li>
<li class="L1"><span class="pln"> vars 變量層</span></li>
<li class="L2"><span class="pln"> tasks 任務(wù)層</span></li>
<li class="L3"><span class="pln"> handlers 觸發(fā)條件</span></li>
<li class="L4"><span class="pln"> files 文件</span></li>
<li class="L5"><span class="pln"> template 模板</span></li>
</ol>
<p>下面介紹下構(gòu)成playbook 的四層結(jié)構(gòu)。</p>
<div style="margin-top: 2em; margin-bottom: 1em;"><span style="color: #1e1e1e; letter-spacing: 2px; border-left: #FF3030 3px solid; border-right: #FF3030 3px solid; padding-left: 8px; padding-right: 8px; font-size: 12pt;"><strong>1、Hosts和Users</strong></span></div>
<p>playbook中的每一個(gè)play的目的都是為了讓某個(gè)或某些主機(jī)以某個(gè)指定的用戶身份執(zhí)行任務(wù)。</p>
<p>hosts 用于指定要執(zhí)行指定任務(wù)的主機(jī)其可以是一個(gè)或多個(gè)由冒號(hào)分隔主機(jī)組。</p>
<p>remote_user 則用于指定遠(yuǎn)程主機(jī)上的執(zhí)行任務(wù)的用戶。<br>
不過remote_user也可用于各task中。也可以通過指定其通過sudo的方式在遠(yuǎn)程主機(jī)上執(zhí)行任務(wù)其可用于play全局或某任務(wù)。<br>
此外甚至可以在sudo時(shí)使用sudo_user指定sudo時(shí)切換的用戶。</p>
<p>示例：</p>
<pre class="brush:php;toolbar:false">- hosts: webnodes
tasks:
- name: test ping connection:
remote_user: test
sudo: yes

play的主體部分是task list。

task list中的各任務(wù)按次序逐個(gè)在hosts中指定的所有主機(jī)上執(zhí)行即在所有主機(jī)上完成第一個(gè)任務(wù)后再開始第二個(gè)。在運(yùn)行自下而下某playbook時(shí)如果中途發(fā)生錯(cuò)誤所有已執(zhí)行任務(wù)都將回滾因此在更正playbook后重新執(zhí)行一次即可。

task的目的是使用指定的參數(shù)執(zhí)行模塊而在模塊參數(shù)中可以使用變量。模塊執(zhí)行是冪等的這意味著多次執(zhí)行是安全的因?yàn)槠浣Y(jié)果均一致。每個(gè)task都應(yīng)該有其name用于playbook的執(zhí)行結(jié)果輸出建議其內(nèi)容盡可能清晰地描述任務(wù)執(zhí)行步驟。如果未提供name則action的結(jié)果將用于輸出。

定義task的可以使用“action: module options”或“module: options”的格式推薦使用后者以實(shí)現(xiàn)向后兼容。如果action一行的內(nèi)容過多也中使用在行首使用幾個(gè)空白字符進(jìn)行換行。

tasks:
- name: make sure apache is running
service: name=httpd state=running
在眾多模塊中只有command和shell模塊僅需要給定一個(gè)列表而無需使用“key=value”格式例如
tasks:
- name: disable selinux
command: /sbin/setenforce 0 如果命令或腳本的退出碼不為零可以使用如下方式替代
tasks:
- name: run this command and ignore the result
shell: /usr/bin/somecommand || /bin/true
或者使用ignore_errors來忽略錯(cuò)誤信息
tasks:
- name: run this command and ignore the result
shell: /usr/bin/somecommand
ignore_errors: True

用于當(dāng)關(guān)注的資源發(fā)生變化時(shí)采取一定的操作。
“notify”這個(gè)action可用于在每個(gè)play的最后被觸發(fā)這樣可以避免多次有改變發(fā)生時(shí)每次都執(zhí)行指定的操作取而代之僅在所有的變化發(fā)生完成后一次性地執(zhí)行指定操作。
在notify中列出的操作稱為handler也即notify中調(diào)用 handler中定義的操作。

注意：在 notify 中定義內(nèi)容一定要和tasks中定義的 - name 內(nèi)容一樣，這樣才能達(dá)到觸發(fā)的效果，否則會(huì)不生效。

- name: template configuration file
template: src=template.j2 dest=/etc/foo.conf
notify:
- restart memcached
- restart apache
handler是task列表這些task與前述的task并沒有本質(zhì)上的不同。
handlers:
- name: restart memcached
service: name=memcached state=restarted
- name: restart apache
service: name=apache state=restarted

tags用于讓用戶選擇運(yùn)行或略過playbook中的部分代碼。ansible具有冪等性因此會(huì)自動(dòng)跳過沒有變化的部分即便如此有些代碼為測(cè)試其確實(shí)沒有發(fā)生變化的時(shí)間依然會(huì)非常地長(zhǎng)。
此時(shí)如果確信其沒有變化就可以通過tags跳過此些代碼片斷。

下面再給出一個(gè)安裝httpd web服務(wù)的示例：

# cat /etc/ansible/playbook/install_web.yml
- hosts: webservers
remote_user: root
gather_fasks: False
vars:
packages: httpd
tasks:
- name: Install httpd
yum: name={{ packages }} state=present
- name: Cofiguration httpd
copy: src=/root/httpd.conf dest=/etc/httpd/conf/httpd.conf
tags: httpd_conf
notify:
- restart httpd
- name: Start httpd
service: name=httpd state=started enabled=no
tags: start
- name:Add centos user
user: name={{ item }} state=absent
tags: adduser
with_items:
- centos
- admin
handlers:
- name: restart httpd
service: name=httpd state=restart

注：上面的代碼沒有考慮ubuntu平臺(tái)，僅僅考慮centos/redhat平臺(tái)。

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