- A
Delete /var/log/app.log and restart the service.
Why wrong: Deleting the log file may cause the service to fail if it expects the file to exist, and does not solve the permission issue.
- B
Add an ACL entry for user nobody with write permission using setfacl.
ACLs allow fine-grained permission assignment to a specific user without changing ownership.
- C
Change the group of /var/log/app.log to nogroup and set group write permission.
Why wrong: This would give write access to all members of nogroup, which may be too broad and not precisely target the nobody user.
- D
Change the permissions of /var/log/app.log to 777.
Why wrong: World-writable permissions are a security risk and not a best practice.
- E
Change the owner of /var/log/app.log to nobody using chown.
Changing the owner to the user that runs the service grants write access.
Quick Answer
The correct answer is to use setfacl to grant write permission to the 'nobody' user, as this method applies fine-grained access control without altering the file's ownership or group, thereby upholding the principle of least privilege. While changing the owner with chown would also work, it unnecessarily elevates the service's access and breaks existing permission structures, making setfacl the more secure and flexible choice for granting write permission to a user. On the LFCS exam, this question tests your understanding of ACLs versus traditional Unix permissions, often appearing as a trap where candidates default to chown without considering security implications. Remember that setfacl allows you to add a specific user entry like setfacl -m u:nobody:w /var/log/app.log, preserving the original owner and group. A helpful mnemonic is "ACL for fine control, chown for full control"—use ACLs when you need to grant write permission to a user without taking ownership away from the system.
LFCS Operation of Running Systems Practice Question
This LFCS practice question tests your understanding of operation of running systems. 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 Linux administrator is troubleshooting a service that is running as the 'nobody' user but keeps failing because it cannot write to its log file. The log file is located at /var/log/app.log. Which TWO of the following methods will allow the service to write to the log file while maintaining security best practices?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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 an ACL entry for user nobody with write permission using setfacl.
Option B is correct because using setfacl to add an ACL entry for the 'nobody' user grants write permission without altering the file's ownership or group, preserving the principle of least privilege. ACLs provide fine-grained access control beyond traditional Unix permissions, allowing the service to write while other users and processes retain their existing access restrictions.
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.
- ✗
Delete /var/log/app.log and restart the service.
Why it's wrong here
Deleting the log file may cause the service to fail if it expects the file to exist, and does not solve the permission issue.
- ✓
Add an ACL entry for user nobody with write permission using setfacl.
Why this is correct
ACLs allow fine-grained permission assignment to a specific user without changing ownership.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Change the group of /var/log/app.log to nogroup and set group write permission.
Why it's wrong here
This would give write access to all members of nogroup, which may be too broad and not precisely target the nobody user.
- ✗
Change the permissions of /var/log/app.log to 777.
Why it's wrong here
World-writable permissions are a security risk and not a best practice.
- ✓
Change the owner of /var/log/app.log to nobody using chown.
Why this is correct
Changing the owner to the user that runs the service grants write access.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Linux Foundation often tests the distinction between ACL-based solutions and traditional permission changes, trapping candidates who overlook that 'nobody' is not a member of 'nogroup' or that 777 is insecure, while both B and E are correct but E is also valid because changing ownership directly grants the user write access without affecting other permissions.
Detailed technical explanation
How to think about this question
ACLs (Access Control Lists) extend the traditional Unix permission model by allowing multiple users and groups to have distinct permissions on a file, stored as extended attributes (xattrs). The setfacl command modifies these entries, and the getfacl command can verify them; ACLs are supported by most Linux filesystems (e.g., ext4, XFS) and are essential in multi-user environments where services run under unprivileged accounts like 'nobody'. A real-world scenario is a web server (e.g., Apache) running as 'nobody' needing to write to logs in /var/log, where changing ownership to 'nobody' (Option E) is also valid but may conflict with other tools expecting root ownership.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Operation of Running Systems — study guide chapter
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FAQ
Questions learners often ask
What does this LFCS question test?
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add an ACL entry for user nobody with write permission using setfacl. — Option B is correct because using setfacl to add an ACL entry for the 'nobody' user grants write permission without altering the file's ownership or group, preserving the principle of least privilege. ACLs provide fine-grained access control beyond traditional Unix permissions, allowing the service to write while other users and processes retain their existing access restrictions.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 30, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LFCS exam.
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