Ansible 剧本与角色 [英] Ansible Playbooks vs Roles

问题描述

根据 Ansible 文档，手册是:

<块引用>

...一个非常简单的配置管理和多机部署系统的基础，不同于现有的任何系统，并且非常适合部署复杂的应用程序.

再一次，根据这些相同的文档，角色是:

<块引用>

...基于已知文件结构自动加载某些 vars_files、任务和处理程序的方法.按角色对内容进行分组还可以轻松地与其他用户共享角色.

然而，这些和它们不同用例之间的区别对我来说并不是很明显.例如，如果我将 /etc/ansible/hosts 文件配置为如下所示:

[数据库]mydb01.example.orgmydb02.example.org[邮件服务器]mymail01.example.orgmymail_dr.example.org

...那么这个[databases]"是什么?条目...角色?或者某个地方的剧本 YAML 文件的名称?还是别的?！?

如果有人能向我解释这些差异，我对 Ansible 的理解将大大提高！

• Playbook vs Role vs [databases] 以及 /etc/ansible/hosts
中的类似条目
• 如果 Playbook 是在 YAML 文件中定义的，那么角色是在哪里定义的?
• 除了位于 Ansible 服务器上的 ansible.cfg 之外，我如何添加/配置 Ansible 和可用的 Playbooks/Roles?例如，当我运行 ansible-playbook someplaybook.yaml 时，Ansible 如何知道在哪里可以找到该剧本?

解决方案

Playbook vs Role vs [databases] 以及/etc/ansible/hosts 中的类似条目

[databases] 是一组主机的单一名称.它允许您通过一个名称引用多个主机.

角色是一组任务和附加文件，用于配置主机以服务于某个角色.

Playbook 是主机和角色之间的映射.

来自文档的示例描述了示例项目.它包含两件事:

• 剧本.site.yml、webservers.yml、fooservers.yml 是剧本.
• 角色:roles/common/ 和 roles/webservers/ 包含相应的 common 和 webservers 角色定义.

在剧本 (webservers.yml) 中，你有类似的东西:

---- hosts: webservers <- 这组主机定义在/etc/ansible/hosts、databases 和 mail_servers 中，例如您的问题角色:<- 这是分配给这些主机的角色列表- 常见的- 网络服务器

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如果 Playbook 是在 YAML 文件中定义的，那么角色是在哪里定义的?

它们在 roles/* 目录中定义.角色主要使用 YAML 文件定义，但也可以包含任何类型的资源(files/、templates/).根据 documentation 角色定义的结构如下:

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• 如果roles/x/tasks/main.yml存在，其中列出的任务将被添加到play中
• 如果roles/x/handlers/main.yml 存在，其中列出的处理程序将被添加到播放中
• 如果roles/x/vars/main.yml存在，其中列出的变量将被添加到play中
• 如果roles/x/meta/main.yml 存在，则其中列出的任何角色依赖项都将添加到角色列表中(1.3 及更高版本)
• 任何复制任务都可以引用roles/x/files/中的文件，而无需相对或绝对路径
• 任何脚本任务都可以引用roles/x/files/中的脚本，而无需相对或绝对路径
• 任何模板任务都可以引用roles/x/templates/中的文件，而无需相对或绝对路径
• 任何包含任务都可以引用roles/x/tasks/中的文件，而无需相对或绝对路径

最重要的文件是roles/x/tasks/main.yml，这里定义了任务，当角色被执行时会被执行.

<块引用>

除了 Ansible 服务器上的 ansible.cfg，我如何添加/配置 Ansible 和可用的 Playbooks/Roles?例如，当我运行 ansible-playbook someplaybook.yaml 时，Ansible 如何知道在哪里可以找到该剧本?

$ ansible-playbook someplaybook.yaml

将在当前目录中查找剧本.

$ ansible-playbook somedir/somedir/someplaybook.yaml

将在 somedir/somedir/ 目录中查找剧本.

您有责任将包含所有剧本和角色的项目放在服务器上.Ansible 与此无关.

According to the Ansible docs, a Playbook is:

...the basis for a really simple configuration management and multi-machine deployment system, unlike any that already exist, and one that is very well suited to deploying complex applications.

And, again, according to those same docs, a Role are:

...ways of automatically loading certain vars_files, tasks, and handlers based on a known file structure. Grouping content by roles also allows easy sharing of roles with other users.

However the distinction between these and their different use cases is not immediately obvious to me. For instance, if I configure my /etc/ansible/hosts file to look like:

[databases]
mydb01.example.org
mydb02.example.org

[mail_servers]
mymail01.example.org
mymail_dr.example.org

...then what is this "[databases]" entry...a role? Or the name of a playbook YAML file somewhere? Or something else?!?

If someone could explain to me the differences on these, my understanding of Ansible would be greatly enhance!

• Playbook vs Role vs [databases] and similar entries in /etc/ansible/hosts
• If Playbooks are defined inside of YAML files, then where are Roles defined?
• Aside from the ansible.cfg living on the Ansible server, how do I add/configure Ansible with available Playbooks/Roles? For instance, when I run ansible-playbook someplaybook.yaml, how does Ansible know where to find that playbook?

解决方案

Playbook vs Role vs [databases] and similar entries in /etc/ansible/hosts

[databases] is a single name for a group of hosts. It allows you to reference multiple hosts by a single name.

Role is a set of tasks and additional files to configure host to serve for a certain role.

Playbook is a mapping between hosts and roles.

Example from documentation describes example project. It contains two things:

• Playbooks. site.yml, webservers.yml, fooservers.yml are playbooks.
• Roles: roles/common/ and roles/webservers/ contain definitions of common and webservers roles accordingly.

Inside playbook (webservers.yml) you have something like:

---
- hosts: webservers <- this group of hosts defined in /etc/ansible/hosts, databases and mail_servers in example from your question
  roles: <- this is list of roles to assign to these hosts
     - common
     - webservers

If Playbooks are defined inside of YAML files, then where are Roles defined?

They are defined inside roles/* directories. Roles are defined mostly using YAML files, but can also contain resources of any types (files/, templates/). According to documentation role definition is structured this way:

• If roles/x/tasks/main.yml exists, tasks listed therein will be added to the play
• If roles/x/handlers/main.yml exists, handlers listed therein will be added to the play
• If roles/x/vars/main.yml exists, variables listed therein will be added to the play
• If roles/x/meta/main.yml exists, any role dependencies listed therein will be added to the list of roles (1.3 and later)
• Any copy tasks can reference files in roles/x/files/ without having to path them relatively or absolutely
• Any script tasks can reference scripts in roles/x/files/ without having to path them relatively or absolutely
• Any template tasks can reference files in roles/x/templates/ without having to path them relatively or absolutely
• Any include tasks can reference files in roles/x/tasks/ without having to path them relatively or absolutely

The most important file is roles/x/tasks/main.yml, here you define tasks, which will be executed, when role is executed.

Aside from the ansible.cfg living on the Ansible server, how do I add/configure Ansible with available Playbooks/Roles? For instance, when I run ansible-playbook someplaybook.yaml, how does Ansible know where to find that playbook?

$ ansible-playbook someplaybook.yaml

Will look for a playbook inside current directory.

$ ansible-playbook somedir/somedir/someplaybook.yaml

Will look for a playbook inside somedir/somedir/ directory.

It's your responsibility to put your project with all playbooks and roles on server. Ansible has nothing to do with that.

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