This LFCS practice question tests your understanding of essential commands. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Which THREE of the following statements about Linux file permissions are correct?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The command 'chmod 400 secret.txt' sets read-only permission for the owner only.
Option B is correct because the numeric permission mode 400 corresponds to read (4) for the owner, with no permissions for the group or others (0 and 0). This sets the file's permissions to r--------, meaning only the owner can read the file, and no one can write or execute it.
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.
✗
The command 'chmod a+w file' removes write permission for all.
Why it's wrong here
a+w adds write permission; a-w removes it.
✓
The command 'chmod 400 secret.txt' sets read-only permission for the owner only.
Why this is correct
400 is r-------- (owner read only).
Related concept
Read the scenario before looking for a memorised answer.
✓
The command 'chmod 755 file' sets permissions to rwxr-xr-x.
Why this is correct
755 corresponds to rwx for owner, r-x for group and others.
Related concept
Read the scenario before looking for a memorised answer.
✓
The command 'chmod u+x script.sh' adds execute permission for the owner.
Why this is correct
u+x adds execute for the user (owner).
Related concept
Read the scenario before looking for a memorised answer.
✗
The command 'chmod 644 file' sets permissions to rw-rw-rw-.
Why it's wrong here
644 sets rw-r--r--, not rw-rw-rw-.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the numeric permission values (e.g., thinking 644 gives rw-rw-rw- instead of rw-r--r--) or misinterpret the symbolic mode syntax, such as assuming 'a+w' removes write permission when it actually adds it.
Detailed technical explanation
How to think about this question
Linux file permissions are stored as a 12-bit value in the inode, with three sets of three bits for owner, group, and others (rwx), plus three special bits (setuid, setgid, sticky). Numeric modes like 755 are octal representations: 7 (rwx) = 4+2+1, 5 (r-x) = 4+0+1. The chmod command updates the inode's permission bits directly; using symbolic modes like 'u+x' modifies only the specified class without affecting other bits.
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 practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The command 'chmod 400 secret.txt' sets read-only permission for the owner only. — Option B is correct because the numeric permission mode 400 corresponds to read (4) for the owner, with no permissions for the group or others (0 and 0). This sets the file's permissions to r--------, meaning only the owner can read the file, and no one can write or execute it.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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