The answer is to verify that the IAM role used for training has permissions to pull from Amazon ECR and to confirm that the image tag in the SageMaker training job definition is correct. This error occurs because SageMaker’s training container cannot retrieve the custom Docker image from the registry, which typically stems from either insufficient IAM permissions for the ecr:GetDownloadUrlForLayer and BatchGetImage actions, or a mistyped or nonexistent image tag. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this question tests your understanding of SageMaker’s dependency on IAM roles for container access, a common trap being that candidates mistakenly focus on network configurations or instance types instead of the role’s resource-based policy. Remember the memory tip: “Pull problems point to permissions or a typo in the tag.”
MLS-C01 Practice Question: Machine Learning Implementation and Operations
This MLS-C01 practice question tests your understanding of machine learning implementation and operations. 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 data scientist is using Amazon SageMaker to train a model. The training job uses a custom Docker image stored in Amazon ECR. The training job fails with an error 'CannotPullContainerError'. Which TWO actions should the data scientist take to resolve this issue? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Confirm that the image tag exists in the ECR repository
Options B and D are correct because checking ECR permissions and verifying the image tag are common causes. Option A is unrelated to pulling. Option C might be needed but not directly. Option E is irrelevant to the error.
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.
✗
Use a public Docker image instead of a custom one
Why it's wrong here
Not necessary; custom images are supported.
✓
Confirm that the image tag exists in the ECR repository
Why this is correct
A missing tag causes CannotPullContainerError.
Related concept
Read the scenario before looking for a memorised answer.
✓
Verify that the IAM role used for training has permissions to pull from ECR
Why this is correct
The execution role needs ecr:GetDownloadUrlForLayer and BatchGetImage.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the training job timeout
Why it's wrong here
Timeout does not affect container pull.
✗
Ensure the training instance has internet access
Why it's wrong here
SageMaker can access ECR without internet if using VPC endpoints.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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.
What to study next
Got this wrong? Here's your next step.
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Machine Learning Implementation and Operations — This question tests Machine Learning Implementation and Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Confirm that the image tag exists in the ECR repository — Options B and D are correct because checking ECR permissions and verifying the image tag are common causes. Option A is unrelated to pulling. Option C might be needed but not directly. Option E is irrelevant to the error.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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