MLS-C01 Practice Question: Machine Learning Implementation and Operations
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 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
✓
Confirm that the image tag exists in the ECR repository
Options B and C are correct because the error 'CannotPullContainerError' typically indicates that the container image cannot be pulled from ECR. This can occur if the image tag does not exist in the repository (B) or if the IAM role used by the SageMaker training job does not have the necessary permissions (e.g., ecr:GetDownloadUrlForLayer, ecr:BatchGetImage) to pull the image (C). Option A is not required; custom images can be used. Option D, increasing the timeout, would not resolve a pull issue. Option E, internet access, is not necessary because SageMaker can access ECR within the AWS network.
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.
- ✓
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.
- ✗
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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