PAS-C01 Operations and Maintenance Practice Question
A company has a CloudFormation stack that creates an EC2 instance with a custom AMI. The stack fails with the error 'Resource creation cancelled' during creation. The engineer checks the stack events and sees that the EC2 instance creation succeeded, but the subsequent creation of an EBS volume failed. What is the MOST likely reason for the failure?
⚠ Common exam trap
The trap here is that candidates misinterpret 'Resource creation cancelled' as a creation failure of the EC2 instance itself, rather than understanding it is a rollback cancellation of a previously successful resource.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The EBS volume creation failed, causing the stack to roll back and cancel the instance
When an EBS volume creation fails in a CloudFormation stack, the stack initiates a rollback of all previously created resources, including the EC2 instance. The 'Resource creation cancelled' error appears for the EC2 instance because its creation was successful but then undone during the rollback, not because it failed initially.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The EC2 instance creation failed and then was cancelled
Why it's wrong here
The events show the instance creation succeeded.
- ✗
The EC2 instance had a DeletionPolicy of Retain, which prevented rollback
Why it's wrong here
A Retain policy would keep the instance, but the error is about creation cancellation.
- ✓
The EBS volume creation failed, causing the stack to roll back and cancel the instance
Why this is correct
If a subsequent resource fails, CloudFormation cancels previously created resources during rollback.
- ✗
The EC2 instance depended on the EBS volume, and the dependency caused a timeout
Why it's wrong here
Dependencies do not cause 'Resource creation cancelled' on a successful resource.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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