AWS Cloud Formation

AWS CloudFormation is programmable yaml to create AWS resources instead of clicking in AWS console.

Define Resources in YAML or JSON, say aws-config.yml
Link aws-config.yml to your account, AWS will create all resources based on aws-config.yml.
Rollback is possible. Shut everything down is possible.
Idempotency: Run same aws-config.yml will not create resources unless aws-config.yml file changed
Resource change only apply on affected resources and its friends
If you change some resources manually without changing aws-config.yml, CloudFormation will undo your changes because it follows your aws-config.yml
Use CloudFormation for things not change often

Structure of aws-config.yml:

AWSTemplateFormatVersion: "2010-09-09"

# Input
Parameters:

# Specify Resources
Resources:

# Returned resources by this template
Outputs:

Fn::Select can be shorten as !Select. You can use these functions in CloudFormation yaml.

!Sub is string interpolation
!GetAttr is to get attribute from resource in template
!Ref — Lookup value of a variable
!Ref "AWS::NoValue"
!Select — The intrinsic function Fn::Select returns a single object from a list of objects by index.
!Join — The intrinsic function Fn::Join appends a set of values into a single value, separated by the specified delimiter.
!Not — Returns true for a condition that evaluates to false or returns false for a condition that evaluates to true.
!Equals — Compares if two values are equal.
!If — Returns one value if the specified condition evaluates to true and another value if the specified condition evaluates to false.