The most likely cause of a CodeBuild file permission error is that the downloaded file has restrictive permissions, such as 600 owned by root, which prevents the Python process from reading it. This occurs because CodeBuild by default runs as root during the build phase, but if the Python script executes under a non-root user—or if the file was downloaded with ownership and permissions that exclude the running user—the process cannot open the file, resulting in a permission denied failure. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how Linux file permissions interact with CodeBuild’s execution context, a common trap where candidates assume root access guarantees read access. Remember the memory tip: “Permissions persist, even for root’s script”—just because the build starts as root doesn’t mean every command inherits that identity, so always verify the user context and file mode when troubleshooting a CodeBuild file permission error.
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. 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.
Exhibit
Refer to the exhibit.
[Container] 2024/01/15 10:00:00 Running command aws s3 cp s3://my-bucket/report.csv .
[Container] 2024/01/15 10:00:02 download: s3://my-bucket/report.csv to ./report.csv
[Container] 2024/01/15 10:00:02 Running command python3 process.py
[Container] 2024/01/15 10:00:05 Error: Unable to open file 'report.csv': Permission denied
The exhibit shows a build log from AWS CodeBuild. The build fails with a permission error when trying to open the downloaded file. What is the most likely cause?
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
✓
The downloaded file has restrictive permissions that the python process cannot read.
The file is downloaded with root ownership and non-root user cannot read it. CodeBuild by default runs as root, but the process.py might be running as a non-root user. However, common cause is that the file was downloaded with restrictive permissions. But more plausible: the file download succeeded but the python script may be running as a different user, or the file permissions are wrong. In CodeBuild, the default user is root, but if the buildspec runs commands as different user, permissions may be an issue. However, a typical cause is that the file permissions are 600 owned by root, and the python process runs as a non-root user. Alternatively, the file might be corrupted. The most likely cause is that the file permissions do not allow read by the user running python. Given the context, option B is correct.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The S3 bucket policy denies access to the object.
Why it's wrong here
Download succeeded, so access is allowed.
✗
The python script is not in the PATH.
Why it's wrong here
Error is about opening file, not script location.
✓
The downloaded file has restrictive permissions that the python process cannot read.
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The file is encrypted and cannot be decrypted.
Why it's wrong here
Download succeeded, so encryption is not blocking.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
Data Store Management — This question tests Data Store Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The downloaded file has restrictive permissions that the python process cannot read. — The file is downloaded with root ownership and non-root user cannot read it. CodeBuild by default runs as root, but the process.py might be running as a non-root user. However, common cause is that the file was downloaded with restrictive permissions. But more plausible: the file download succeeded but the python script may be running as a different user, or the file permissions are wrong. In CodeBuild, the default user is root, but if the buildspec runs commands as different user, permissions may be an issue. However, a typical cause is that the file permissions are 600 owned by root, and the python process runs as a non-root user. Alternatively, the file might be corrupted. The most likely cause is that the file permissions do not allow read by the user running python. Given the context, option B is correct.
What should I do if I get this DEA-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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