DVA-C02 Development with AWS Services Practice Question
A company is using AWS CodeDeploy to deploy an application to an Auto Scaling group. The deployment fails with the error 'The overall deployment failed because too many individual instances failed to deploy.' The CodeDeploy agent logs show that the BeforeInstall lifecycle event script returned a non-zero exit code. What is the MOST likely cause of this issue?
⚠ Common exam trap
A common mix-up: candidates confuse a script failure (non-zero exit code) with infrastructure or permission issues, but the question explicitly provides the agent log detail pointing to the BeforeInstall script, making the script bug the direct and most likely cause.
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 BeforeInstall script has a bug that causes it to exit with a non-zero status.
The error message explicitly states that the CodeDeploy agent logs show the BeforeInstall lifecycle event script returned a non-zero exit code. This directly indicates that the script itself failed during execution, which is the most likely cause of the deployment failure. The BeforeInstall script is a custom script run by the CodeDeploy agent on each instance, and a non-zero exit code signals an error condition that halts the deployment for that instance.
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 application revision is missing from the S3 bucket.
Why it's wrong here
If the application revision were genuinely missing from the specified S3 bucket, the CodeDeploy agent would encounter a download error during the DownloadBundle lifecycle event. This failure would manifest as an inability to retrieve the deployment artifacts, resulting in an S3 access or file not found error, rather than an execution error from a BeforeInstall script that was never successfully downloaded or run.
- ✓
The BeforeInstall script has a bug that causes it to exit with a non-zero status.
Why this is correct
CodeDeploy strictly interprets any non-zero exit status from a lifecycle event script, such as BeforeInstall, as a critical failure. This indicates that the script, intended to prepare the environment or install prerequisites, did not complete successfully. Consequently, the deployment on that specific instance is immediately halted, and the overall deployment is marked as failed, preventing further potentially problematic steps.
- ✗
The IAM instance profile does not have permissions to call CodeDeploy APIs.
Why it's wrong here
Insufficient IAM instance profile permissions would prevent the CodeDeploy agent from performing fundamental operations, such as registering with the CodeDeploy service or accessing the S3 bucket to download the application revision. Such a permissions issue would typically manifest as an agent registration failure or a DownloadBundle error, occurring long before any BeforeInstall script could even be executed on the instance.
- ✗
The CodeDeploy agent is not running on the instances.
Why it's wrong here
If the CodeDeploy agent is not actively running on the target instance, the CodeDeploy service cannot establish communication or initiate any deployment steps. This scenario would result in the deployment timing out or remaining in a 'Pending' state indefinitely, as the agent is responsible for receiving commands and executing all lifecycle events, including the BeforeInstall script.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.