The answer is iam:PassRole on the SageMaker execution role. When a training job using a SageMaker built-in algorithm like XGBoost is launched, SageMaker must assume the execution role you specify to pull the algorithm container image from Amazon ECR, access training data in S3, and write output. Without the iam:PassRole permission, the CreateTrainingJob API call itself fails with an access denied error before SageMaker can even attempt to pull the ECR image or interact with S3. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this is a classic trap: candidates often focus on missing ECR permissions like ecr:GetDownloadUrlForLayer or missing S3 actions, but the root cause is almost always the missing iam:PassRole on the notebook instance role. The exam tests your understanding that PassRole is a prerequisite for any SageMaker job that needs to assume a different role. Memory tip: “Pass first, pull later”—without PassRole, SageMaker never gets the chance to use ECR or S3 permissions.
MLS-C01 Modeling Practice Question
This MLS-C01 practice question tests your understanding of modeling. 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.
Refer to the exhibit. An IAM policy is attached to a SageMaker notebook instance role. A data scientist is trying to train a model using the SageMaker built-in XGBoost algorithm with training data in 'my-bucket/training-data/' and expects output in 'my-bucket/output/'. The training job fails with an access denied error. What is the most likely missing permission?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
iam:PassRole on the SageMaker execution role.
The training job uses the SageMaker built-in algorithm, which downloads the training data from S3 and uploads output. The policy allows s3:GetObject on training-data and s3:PutObject on output. However, SageMaker also needs to read the algorithm image from ECR (elasticcontainerregistry). The missing permission is likely ecr:GetDownloadUrlForLayer or ecr:BatchGetImage. Also, SageMaker needs to pass roles. But the error is 'access denied', likely from ECR. Option A (ecr:GetAuthorizationToken) is needed to authenticate, but typically SageMaker uses the role to pull images. Option B (s3:ListBucket) is needed if the training job lists objects. Option C (sagemaker:DescribeTrainingJob) is not needed for execution. Option D (iam:PassRole) is needed for the training job to assume the role. Actually, SageMaker needs iam:PassRole to pass the execution role to the training job. But the error 'access denied' could be due to missing iam:PassRole. However, the policy does not include iam:PassRole. The most likely missing permission is iam:PassRole. Let's check: The policy allows creating training job, but the training job also needs to pass a role to SageMaker. Without iam:PassRole, the API call fails. So D is correct. But also ECR permissions might be needed. However, IAM PassRole is a common missing permission. I'll go with D.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
iam:PassRole on the SageMaker execution role.
Why this is correct
The policy is missing iam:PassRole, which is required to allow SageMaker to assume the execution role for the training job.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
ecr:GetAuthorizationToken on the ECR repository.
Why it's wrong here
While ECR permissions are needed, the most immediate error is often iam:PassRole.
✗
s3:ListBucket on the S3 bucket.
Why it's wrong here
ListBucket is not required for GetObject; the training job has GetObject permission.
✗
sagemaker:DescribeTrainingJob on the training job.
Why it's wrong here
DescribeTrainingJob is not needed to create a training job.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related MLS-C01 questions on access control and AAA configuration.
Modeling — This question tests Modeling — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: iam:PassRole on the SageMaker execution role. — The training job uses the SageMaker built-in algorithm, which downloads the training data from S3 and uploads output. The policy allows s3:GetObject on training-data and s3:PutObject on output. However, SageMaker also needs to read the algorithm image from ECR (elasticcontainerregistry). The missing permission is likely ecr:GetDownloadUrlForLayer or ecr:BatchGetImage. Also, SageMaker needs to pass roles. But the error is 'access denied', likely from ECR. Option A (ecr:GetAuthorizationToken) is needed to authenticate, but typically SageMaker uses the role to pull images. Option B (s3:ListBucket) is needed if the training job lists objects. Option C (sagemaker:DescribeTrainingJob) is not needed for execution. Option D (iam:PassRole) is needed for the training job to assume the role. Actually, SageMaker needs iam:PassRole to pass the execution role to the training job. But the error 'access denied' could be due to missing iam:PassRole. However, the policy does not include iam:PassRole. The most likely missing permission is iam:PassRole. Let's check: The policy allows creating training job, but the training job also needs to pass a role to SageMaker. Without iam:PassRole, the API call fails. So D is correct. But also ECR permissions might be needed. However, IAM PassRole is a common missing permission. I'll go with D.
What should I do if I get this MLS-C01 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related MLS-C01 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Authentication checks who the user is.
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Question Discussion
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