Puppet

自定义fact实现的四种方式介绍

Resources and the RAL

Resources: Imagine a system’s configuration as a collection of many independent atomic units; call them “resources.”
- 资源可分类
- 资源类型描述抽离于它的具体操作步骤
- Puppet 指定资源的期望状态，而不是直接指定具体操作
- 以上三点组成 Puppet 的资源抽象层（RAL）， RAL 包括 types（高级别抽象模型）和 providers（平台相关实现），这样可以使用平台无关的方式来描述资源得期望状态。

每个资源（Resource ）的描述包括： resource type, one title, a number of attributes, each attribute has a value

    user { 'dave':
      ensure     => present,
      uid        => '507',
      gid        => 'admin',
      shell      => '/bin/ksh',
      home       => '/home/dave',
      managehome => true,
    }

This syntax is called a resource declaration

Resource Types : puppet_core_types_cheatsheet.pdf, the type references
puppet describe : The puppet describe subcommand can list info about the currently installed resource types on a given machine.
puppet resource: Puppet includes a command called puppet resource, which can interactively inspect and modify resources on a single system. Usage:
```
# puppet resource <TYPE> [<NAME>] [ATTRIBUTE=VALUE ...]
```

Manifests

.pp: Puppet programs are called “manifests,” and they use the .pp file extension.
完整语法链接： lang resources
- 大括号，冒号，逗号要正确
- 大小写敏感。类型（type）和属性（attributes）名必须小写
- 字符串值的书写: datatypes
- All types have a special attribute called the namevar, 该属性缺失就默认以 title 替代
Before being applied, manifests get compiled into a document called a catalog
puppet apply <.pp file >
Puppet agent/master

Resource Ordering

You can embed relationship information in a resource with the before, require, notify, and subscribe metaparameters.
You can also declare relationships outside a resource with the → and ~> chaining arrows.
Relationships can be either ordering (this before that) or ordering-with-notification (this before that, and tell that whether this was changed).
Puppet’s relationship behaviors and syntaxes are documented in the Puppet reference manual page on relationships.
The ordering setting in puppet.conf determines the order in which unrelated resources are applied.

Variables, Conditionals, and Facts

Variables: 语法类似 php, 但实际是常量，只能被赋值一次，不能修改。
Conditionals: if, elseif, else, case,default
Puppet has a bunch of built-in, pre-assigned variables that you can use.
Facts: facts ,Puppet uses a tool called Facter, which discovers some system information, normalizes it into a set of variables, and passes them off to Puppet. Puppet’s compiler then has access to those facts when it’s reading a manifest.
- List of core facts
- The custom facts guild

Modules and Classes

Classes are named blocks of Puppet code, which can be created in one place and invoked elsewhere.
Puppet 的 class 更像是宏，但拥有变量域。
include <class name> 来起作用。
Modules:
- Modules are just directories with files, arranged in a specific, predictable structure. The manifest files within a module have to obey certain naming restrictions.
- Puppet looks for modules in a specific place (or list of places). This set of directories is known as the modulepath, which is a configurable setting
- If a class is defined in a module, you can declare that class by name in any manifest. Puppet will automatically find and load the manifest that contains the class definition.
- 一个 module 就是一个路径，模块名就是路径名
- module layout: 模块包含子文件夹manifests,files,templates等等, 详看 a page of info about module layout 以及 module cheat sheet.
- module 静态文件(files/下)的引用格式:
```
puppet:///modules/模块名/文件名(可包括files下的子路径)
```
  例如:
```
puppet:///modules/ntp/config_files/linux/ntp.conf.el
```
  引用ntp模块下的files/config_files/linux/ntp.conf.el文件.
puppet.conf: The Puppet config file is called puppet.conf, and in Puppet Enterprise it is located at /etc/puppetlabs/puppet/puppet.conf
The format of puppet.conf is explained in the configuration docs

Puppet Forge: 模块仓库. 使用方式:install module:

$ sudo puppet module install puppetlabs-mysql//forge 里模块名有用户名前缀

List all installed modules:

$ sudo puppet module list

Templates

Templates are saved as files with the .erb extension. and be stored in the templates/ directory of any module. There can be any number of subdirectories inside templates/.

Use a template by the function template:

 file {'/etc/foo.conf':
  ensure => file,
  require => Package['foo'],
  content => template('foo/foo.conf.erb'),
}

template参数格式为<MODULE NAME>/<FILENAME INSIDE TEMPLATES DIRECTORY>.

Use a template by the function inline_template