Parameters for customization in AWS - Step-by-Step Execution

Process Flow - Parameters for customization

Define Parameter

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Use Parameter in Template

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Deploy Stack with Parameter Value

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CloudFormation Reads Parameter

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Resource Created Using Parameter

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Stack Ready with Custom Config

Parameters let you customize AWS CloudFormation stacks by defining inputs that change resource settings during deployment.

Execution Sample

AWS

Parameters:
  InstanceTypeParam:
    Type: String
    Default: t2.micro
Resources:
  MyEC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: !Ref InstanceTypeParam

This template defines a parameter for EC2 instance type and uses it to set the instance type when creating the EC2 resource.

Process Table

Step	Action	Parameter Value	Resource Property Set	Result
1	Define parameter InstanceTypeParam	t2.micro (default)	N/A	Parameter ready for input
2	Deploy stack without override	t2.micro	InstanceType = t2.micro	EC2 instance will be t2.micro
3	Deploy stack with override 'm5.large'	m5.large	InstanceType = m5.large	EC2 instance will be m5.large
4	CloudFormation creates EC2 instance	m5.large	InstanceType = m5.large	EC2 instance launched with m5.large
5	Stack deployment complete	m5.large	InstanceType = m5.large	Stack ready with customized instance type

💡 Stack deployment ends after resource creation using parameter value

Status Tracker

Variable	Start	After Step 2	After Step 3	Final
InstanceTypeParam	t2.micro (default)	t2.micro	m5.large	m5.large
MyEC2Instance.InstanceType	N/A	t2.micro	m5.large	m5.large

Key Moments - 2 Insights

Why does the EC2 instance type change when I deploy the stack with a different parameter value?

Because the parameter value overrides the default and is used in the resource property, as shown in execution_table step 3 where InstanceTypeParam changes from default to 'm5.large'.

What happens if I do not provide a parameter value during deployment?

The default parameter value is used, as shown in execution_table step 2 where the instance type remains 't2.micro'.

Visual Quiz - 3 Questions

Look at the execution table, what is the InstanceTypeParam value at step 3?

A m5.large

B t2.micro

C t3.medium

D No value set

💡 Hint

Check the 'Parameter Value' column at step 3 in the execution_table.

At which step does CloudFormation create the EC2 instance using the parameter value?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Action' column describing resource creation in the execution_table.

If you remove the default value from the parameter, what will happen during deployment without an override?

A Uses a random instance type

B Deployment fails due to missing parameter

C Uses t2.micro automatically

D Creates instance with no type

💡 Hint

Parameters without defaults require a value at deployment, see how default is used in step 2.

Concept Snapshot

Parameters let you customize AWS CloudFormation stacks.
Define parameters with type and optional default.
Use !Ref to insert parameter values into resources.
During deployment, provide values or use defaults.
Resources use these values to configure settings.
This enables flexible, reusable templates.

Full Transcript

Parameters in AWS CloudFormation allow you to customize your infrastructure by defining inputs that can change resource properties during deployment. You define a parameter with a type and optionally a default value. In your template, you use the parameter with !Ref to set resource properties. When deploying the stack, you can provide a value to override the default. CloudFormation reads the parameter value and creates resources accordingly. This process lets you reuse templates for different configurations without changing the template code itself.