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Parameters In AWS CloudFormation

This article describes the parameters in AWS CloudFormation.

Purpose

In AWS CloudFormation, parameters act as inputs to a CloudFormation stack, allowing users to customize how resources are provisioned without modifying the template.

Create A YAML File

To begin with, create a YAML file with the following content.

AWSTemplateFormatVersion: "2010-09-09"
Description: Create an S3 bucket with a parameter for the bucket name.

Parameters:
  BucketName:
    Type: String
    Description: The name of the S3 bucket to create.
    MinLength: 3
    MaxLength: 6
    AllowedPattern: '^[a-z0-9.-]*$'
    ConstraintDescription: "Bucket name must only contain lowercase letters, numbers, periods, and hyphens."

Resources:
  MyS3Bucket:
    Type: 'AWS::S3::Bucket'
    Properties:
      BucketName: !Ref BucketName

In this above YAML, we pass the bucket name as a parameter.

Create A Stack

While creating the stack, you have an option to specify the parameter.

Picture showing creating a Cloudformation stack with parameters

An error will occur if the input provided does not adhere to the required constraints.

Picture showing the error message when constraint rule is not followed

Posted By -	Karan Gupta

Posted On -	Thursday, January 30, 2025

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