- A
Configure the ECR repository as public.
Why wrong: Public repository is not needed.
- B
Add a command in the buildspec to run 'aws ecr get-login-password --region <region> | docker login --username AWS --password-stdin <account>.dkr.ecr.<region>.amazonaws.com'.
This authenticates Docker to ECR.
- C
Create an ECR lifecycle policy to expire untagged images.
Why wrong: Not related to authentication.
- D
Ensure the CodeBuild service role has permissions for ecr:GetAuthorizationToken and ecr:Push.
IAM permissions are required.
- E
Run 'docker login' with ECR credentials in the buildspec.
Why wrong: Docker login is not the standard for ECR.
Question 1,366 of 1,750
Fixing AWS CodeBuild ECR Push Authentication Error
This DOP-C02 practice question tests your understanding of sdlc automation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is using AWS CodeBuild to build a Docker image and push it to Amazon ECR. The buildspec.yaml includes commands to build and tag the image. However, the push to ECR fails with an authentication error. Which TWO actions should the DevOps engineer take to resolve this?
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
✓
Add a command in the buildspec to run 'aws ecr get-login-password --region <region> | docker login --username AWS --password-stdin <account>.dkr.ecr.<region>.amazonaws.com'.
Option B is correct because the `aws ecr get-login-password` command retrieves a temporary authentication token from the ECR service, which is then piped to `docker login` to authenticate the Docker client against the private ECR registry. This is the standard AWS-recommended method for authenticating Docker to ECR in automated build environments like CodeBuild, as it avoids hardcoding long-lived credentials.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the ECR repository as public.
Why it's wrong here
Public repository is not needed.
- ✓
Add a command in the buildspec to run 'aws ecr get-login-password --region <region> | docker login --username AWS --password-stdin <account>.dkr.ecr.<region>.amazonaws.com'.
Why this is correct
This authenticates Docker to ECR.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create an ECR lifecycle policy to expire untagged images.
Why it's wrong here
Not related to authentication.
- ✓
Ensure the CodeBuild service role has permissions for ecr:GetAuthorizationToken and ecr:Push.
Why this is correct
IAM permissions are required.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Run 'docker login' with ECR credentials in the buildspec.
Why it's wrong here
Docker login is not the standard for ECR.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think simply running `docker login` with static credentials (Option E) is sufficient, but they overlook that ECR requires a dynamically generated token via `get-login-password`, and that the CodeBuild service role must have the correct IAM permissions (Option D) for the authentication flow to succeed.
Detailed technical explanation
How to think about this question
The `aws ecr get-login-password` command uses the AWS SDK to call the ECR `GetAuthorizationToken` API, which returns a base64-encoded token valid for 12 hours. This token is then passed to `docker login` via stdin, allowing the Docker client to authenticate using the AWS account ID and region-specific registry endpoint. Under the hood, the token is an AWS Signature V4-signed authorization header that the Docker client uses for subsequent push/pull operations, and the IAM permissions required are `ecr:GetAuthorizationToken` (to obtain the token) and `ecr:Push` (to upload images).
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a command in the buildspec to run 'aws ecr get-login-password --region <region> | docker login --username AWS --password-stdin <account>.dkr.ecr.<region>.amazonaws.com'. — Option B is correct because the `aws ecr get-login-password` command retrieves a temporary authentication token from the ECR service, which is then piped to `docker login` to authenticate the Docker client against the private ECR registry. This is the standard AWS-recommended method for authenticating Docker to ECR in automated build environments like CodeBuild, as it avoids hardcoding long-lived credentials.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Same concept, more angles
1 more ways this is tested on DOP-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company uses AWS CodeBuild to build a Docker image and push it to Amazon ECR. The buildspec.yml includes a 'post_build' phase command to tag the image. The build fails with 'unauthorized: authentication required'. What must be done to resolve this?
easy- ✓ A.Add 'ecr:InitiateLayerUpload' and 'ecr:CompleteLayerUpload' permissions to the CodeBuild service role.
- B.Use the 'docker login' command with AWS CLI in the build phase.
- C.Install the AWS CLI in the CodeBuild build environment.
- D.Create a new IAM user with ECR permissions and store the keys in CodeBuild environment variables.
Why A: The error 'unauthorized: authentication required' indicates that CodeBuild's IAM role lacks the necessary permissions to push the Docker image to Amazon ECR. The correct resolution is to add the specific ECR permissions 'ecr:InitiateLayerUpload' and 'ecr:CompleteLayerUpload' to the CodeBuild service role, as these are required for the Docker push operation to upload image layers. Without these permissions, the ECR API rejects the push even if other permissions like 'ecr:GetAuthorizationToken' are present.
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Last reviewed: Jul 4, 2026
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