CodeDeploy Agent Not Installed — Deployment Failure Root Cause
A company uses AWS CodeDeploy to deploy a web application to an Auto Scaling group of Amazon EC2 instances. The deployment fails with the error 'The overall deployment failed because too many individual instances failed deployment, too few healthy instances are available for deployment, or some instances in your deployment group are experiencing problems.' The application is deployed to the instances using an in-place deployment. The instances are running Amazon Linux 2. What should the DevOps engineer check first?
Quick Answer
The correct first step is to verify that the AWS CodeDeploy agent is installed and running on each EC2 instance. This is because CodeDeploy relies on a lightweight agent installed on the instance to poll for deployment instructions, download the revision, and execute the deployment lifecycle hooks; without a running agent, the instance cannot participate in the deployment at all, leading to the generic failure error about too many individual instances failing. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this question tests your ability to prioritize the most fundamental prerequisite for in-place deployments on Amazon Linux 2, often serving as a trap where candidates jump to IAM roles or security groups first. A common memory tip is to think of the agent as the “heartbeat” of CodeDeploy—if it’s not beating, nothing else matters. Remember: agent first, permissions second, network third.
⚠ Common exam trap
The trap here is that candidates often jump to IAM permissions (Option D) as the first troubleshooting step, but the error message's reference to 'individual instances failed' directly points to the agent not running on the instances, which is a more immediate and common cause than permission issues.
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
✓
Verify that the AWS CodeDeploy agent is installed and running on each EC2 instance.
The error message indicates that individual instances failed deployment, which is most commonly caused by the AWS CodeDeploy agent not running or not being installed on the EC2 instances. For an in-place deployment on Amazon Linux 2, the CodeDeploy agent must be installed and actively running to receive and execute deployment commands from the CodeDeploy service. If the agent is missing or stopped, the instance cannot participate in the deployment, leading to the 'too many individual instances failed' error.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Check the security group rules for the EC2 instances.
Why it's wrong here
Security groups are not the primary cause of this error.
- ✗
Check the application's port availability.
Why it's wrong here
Port availability is not related to the agent.
- ✓
Verify that the AWS CodeDeploy agent is installed and running on each EC2 instance.
Why this is correct
Without the agent, the instance cannot receive deployment instructions.
- ✗
Verify that the IAM instance profile associated with the instances has the correct permissions.
Why it's wrong here
While important, the agent must be running first.
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1 more way this is tested on DOP-C02
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Variation 1. A company uses 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 deployment, too few healthy instances are available for deployment, or some instances in your deployment group are experiencing problems.' The deployment is set to 'AllAtOnce'. The application revision is a simple index.html. What is the most likely cause?
hard- ✓ A.The CodeDeploy agent is not installed or running on the EC2 instances.
- B.The IAM instance profile does not have permissions to download from Amazon S3.
- C.The application revision is not a compressed archive.
- D.The deployment configuration 'AllAtOnce' is incompatible with Auto Scaling groups.
Why A: The error message indicates that too many instances failed deployment, which is typical when the CodeDeploy agent is not running on the EC2 instances. With an 'AllAtOnce' deployment, all instances are targeted simultaneously, so if the agent is missing on every instance, all will fail immediately, causing the overall deployment to fail. The simple index.html revision is not the issue; the agent is required to execute the AppSpec file and pull the revision from S3 or GitHub.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-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 DOP-C02 exam.