Creating stacks in AWS - Practice Exercises

Challenge - 5 Problems

❓ service_behavior

intermediate

Stack Creation Behavior with Missing Parameters

You create an AWS CloudFormation stack using a template that requires a parameter named InstanceType. You run the create-stack command without specifying this parameter. What will happen?

A The stack creation fails immediately with a validation error about the missing parameter.

B The stack creation waits indefinitely for the parameter to be provided.

C The stack creation succeeds but the resource using <code>InstanceType</code> is skipped.

D The stack is created with a default value for <code>InstanceType</code> if defined in the template.

💡 Hint

Think about how CloudFormation handles parameters with and without default values.

If a parameter has a default value defined in the template, CloudFormation uses it when the parameter is not provided during stack creation. Otherwise, it raises a validation error.

❓ Architecture

intermediate

Stack Dependency Management

You have two CloudFormation stacks: NetworkStack creates a VPC, and AppStack creates EC2 instances inside that VPC. How should you ensure AppStack only creates resources after NetworkStack is complete?

A Create <code>AppStack</code> first, then create <code>NetworkStack</code> after.

B Manually wait for <code>NetworkStack</code> to complete before creating <code>AppStack</code>.

C Use the <code>DependsOn</code> attribute in <code>AppStack</code> to depend on <code>NetworkStack</code>.

D Use stack outputs and import values from <code>NetworkStack</code> in <code>AppStack</code>.

💡 Hint

Consider how CloudFormation stacks share information and dependencies.

CloudFormation does not support DependsOn between stacks. Instead, you export outputs from one stack and import them in another to create implicit dependencies.

❓ security

advanced

IAM Role Permissions for Stack Creation

You want to automate CloudFormation stack creation using an IAM role. Which permission is required for the role to successfully create stacks?

A cloudformation:CreateStack

B ec2:CreateInstance

C iam:PassRole

D s3:PutObject

💡 Hint

Focus on the permissions related to CloudFormation stack operations.

The cloudformation:CreateStack permission allows creating stacks. Other permissions may be needed depending on resources, but this is essential.

✅ Best Practice

advanced

Stack Update Strategy to Avoid Downtime

You need to update a CloudFormation stack that runs a web application. What is the best practice to avoid downtime during the update?

A Delete the stack and create a new one with updated resources.

B Use stack update with <code>UpdatePolicy</code> to perform rolling updates.

C Manually stop the application, update the stack, then start the application.

D Update the stack and immediately rollback if errors occur.

💡 Hint

Look for CloudFormation features that help update resources without downtime.

The UpdatePolicy attribute allows rolling updates for resources like Auto Scaling groups, minimizing downtime.

🧠 Conceptual

expert

Stack Drift Detection Outcome

You run drift detection on a CloudFormation stack and it reports drift on one resource. What does this mean?

A The stack has pending updates waiting to be applied.

B The resource was deleted outside CloudFormation.

C The resource's actual configuration differs from the stack template.

D The stack is in rollback state due to an error.

💡 Hint

Think about what drift detection compares.

Drift detection compares the actual resource configuration with the expected configuration defined in the stack template. Drift means they differ.

Practice

1. What is the main purpose of creating a stack in AWS CloudFormation?

easy

A. To group related cloud resources for easy management

B. To write code for AWS Lambda functions

C. To monitor AWS billing and usage

D. To create user accounts in AWS IAM

Solution

1. Step 1: Understand what a stack represents

   A stack is a collection of AWS resources that you manage as a single unit.

2. Step 2: Identify the purpose of grouping resources

   Grouping resources simplifies deployment, updates, and deletion.

3. Final Answer:

   To group related cloud resources for easy management -> Option A

4. Quick Check:

   Stack = Group resources [OK]

Hint: Stacks group resources to manage them together [OK]

Common Mistakes:

• Confusing stacks with user accounts
• Thinking stacks are for billing
• Mixing stacks with Lambda code writing

2. Which AWS CLI command is used to create a stack from a template file named template.yaml?

easy

A. aws s3 create-bucket --template template.yaml

B. aws cloudformation create-stack --stack-name MyStack --template-body file://template.yaml

C. aws cloudformation deploy --stack-name MyStack --template-file file://template.yaml

D. aws ec2 create-stack --template-file template.yaml

Solution

1. Step 1: Identify the correct AWS service and command

   Creating stacks uses the AWS CloudFormation service and the command is create-stack.

2. Step 2: Check the correct syntax for template file input

   The template file is specified with --template-body file://filename.

3. Final Answer:

   aws cloudformation create-stack --stack-name MyStack --template-body file://template.yaml -> Option B

4. Quick Check:

   Use create-stack with --template-body file:// [OK]

Hint: Use create-stack with --template-body file:// [OK]

Common Mistakes:

• Using wrong AWS service like EC2 or S3
• Using --template-file instead of --template-body
• Confusing create-stack with deploy command

3. Given this AWS CLI command:
aws cloudformation create-stack --stack-name TestStack --template-body file://template.yaml --parameters ParameterKey=Env,ParameterValue=prod
What will happen when this command runs?

medium

A. The command will fail because parameters must be in JSON format

B. The stack will be created with default parameter values ignoring Env

C. The stack will be created but the Env parameter will be ignored

D. A stack named TestStack is created using the template with Env parameter set to prod

Solution

1. Step 1: Understand parameter usage in create-stack command

   The --parameters option allows passing key-value pairs to customize the stack.

2. Step 2: Check the syntax correctness

   The syntax ParameterKey=Env,ParameterValue=prod is valid for AWS CLI parameters.

3. Final Answer:

   A stack named TestStack is created using the template with Env parameter set to prod -> Option D

4. Quick Check:

   Parameters customize stack creation [OK]

Hint: Parameters use ParameterKey= and ParameterValue= pairs [OK]

Common Mistakes:

• Thinking parameters must be JSON
• Assuming parameters are ignored if passed
• Confusing parameter syntax with other commands

4. You run this command to create a stack:
aws cloudformation create-stack --stack-name MyStack --template-body file://template.yaml
But you get an error: Template format error: YAML not well-formed.
What is the most likely cause?

medium

A. The template.yaml file has syntax errors in YAML formatting

B. The stack name MyStack is invalid

C. The AWS CLI command is missing the region parameter

D. The template file path is incorrect

Solution

1. Step 1: Analyze the error message

   The error says "YAML not well-formed" which means the template file has syntax issues.

2. Step 2: Check other possible causes

   Stack name and region issues cause different errors; file path errors cause file not found errors.

3. Final Answer:

   The template.yaml file has syntax errors in YAML formatting -> Option A

4. Quick Check:

   YAML errors cause template format error [OK]

Hint: Check YAML syntax carefully for formatting errors [OK]

Common Mistakes:

• Assuming stack name causes YAML errors
• Ignoring file path correctness
• Forgetting to check template syntax

5. You want to create a stack that launches an EC2 instance with a parameter to choose the instance type. Your template uses a parameter named InstanceType. Which AWS CLI command correctly creates the stack with t3.micro as the instance type?

hard

A. aws cloudformation deploy --stack-name EC2Stack --template-file file://ec2.yaml --parameter-overrides InstanceType=t3.micro

B. aws cloudformation create-stack --stack-name EC2Stack --template-body file://ec2.yaml --parameters InstanceType=t3.micro

C. aws cloudformation create-stack --stack-name EC2Stack --template-body file://ec2.yaml --parameters ParameterKey=InstanceType,ParameterValue=t3.micro

D. aws ec2 run-instances --instance-type t3.micro --template-file ec2.yaml

Solution

1. Step 1: Identify the correct command and syntax for stack creation with parameters

   The create-stack command uses --parameters ParameterKey=key,ParameterValue=value syntax.

2. Step 2: Verify the parameter key and value match the template

   The parameter key is InstanceType and value is t3.micro, correctly formatted in aws cloudformation create-stack --stack-name EC2Stack --template-body file://ec2.yaml --parameters ParameterKey=InstanceType,ParameterValue=t3.micro.

3. Final Answer:

   aws cloudformation create-stack --stack-name EC2Stack --template-body file://ec2.yaml --parameters ParameterKey=InstanceType,ParameterValue=t3.micro -> Option C

4. Quick Check:

   Use ParameterKey= and ParameterValue= for parameters [OK]

Hint: Use ParameterKey= and ParameterValue= pairs for parameters [OK]

Common Mistakes:

• Using wrong parameter syntax
• Confusing deploy with create-stack
• Using EC2 CLI instead of CloudFormation