CloudFormation Templates

• It is a JSON or YAML formatted text file.
• save them with any extension, such as
  • .json
  • .yaml
  • .template
  • .txt
• CloudFormation uses them for building AWS resources.
• Example template with EC2 instance needs
  • instance type
  • the AMI ID
  • block device mappings
  • and its Amazon EC2 key pair name.
• Whenever you create a stack, you also specify a template that AWS CloudFormation uses to create whatever you described in the template.
• For JSON, it follows the ECMA-404 JSON standard
• For XAML, supports the YAML Version 1.1 specification with exceptions, as
  • The binary, omap, pairs, set, and timestamp tags
  • Aliases
  • Hash merges

JSON formatted template layout

{

  “AWSTemplateFormatVersion” : “version date”,

  “Description” : “JSON string”,

  “Metadata” : {

    template metadata

  },

  “Parameters” : {

    set of parameters

  },

  “Mappings” : {

    set of mappings

  },

  “Conditions” : {

    set of conditions

  },

  “Transform” : {

    set of transforms

  },

  “Resources” : {

    set of resources

  },

  “Outputs” : {

    set of outputs

  } }

XAML formatted template layout

—

AWSTemplateFormatVersion: “version date”

Description:

  String

Metadata:

  template metadata

Parameters:

  set of parameters

Mappings:

  set of mappings

Conditions:

  set of conditions

Transform:

  set of transforms

Resources:

  set of resources

Outputs: set of outputs

Template Sections

• Templates has many sections.
• The Resources section is the only required section.
• Some sections in a template can be in any order.
• Various templates sections are
  • Resources (required) – stack resources and their properties
  • Format Version (optional) – template format version that template conforms to.
  • Description (optional) – text string describing the template. Must always follow template format version section.
  • Metadata (optional) – Objects that provide additional information about the template.
  • Parameters (optional) – Values to pass to template at runtime
  • Mappings (optional) – A mapping of keys and associated values to specify conditional parameter values, similar to a lookup table.
  • Conditions (optional) – Conditions controlling resource creation or resource property assignment during stack creation or update.
  • Transform (optional) – For serverless applications, specifying version of AWS Serverless Application Model to use.
  • Outputs (optional) – Describes values returned whenever viewing stack’s properties.