This LPIC-1 practice question tests your understanding of gnu and unix 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 are valid symbolic mode expressions for the chmod command?
u+x
Adds execute permission for the user.
755
Why wrong: 755 is numeric mode, not symbolic.
a+rwx
Adds read, write, execute for all categories.
c+r
Why wrong: 'c' is not a valid category (u, g, o, a are valid).
g-w
Removes write permission for the group.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
u+x
Option A is correct because 'u+x' is a valid symbolic mode expression for chmod, where 'u' stands for the user (owner), '+' adds a permission, and 'x' is the execute permission. This syntax follows the POSIX standard for symbolic modes, allowing precise modification of file permissions without specifying an absolute octal value.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
u+x
Why this is correct
Adds execute permission for the user.
Related concept
Read the scenario before looking for a memorised answer.
755
Why it's wrong here
755 is numeric mode, not symbolic.
a+rwx
Why this is correct
Adds read, write, execute for all categories.
Related concept
Read the scenario before looking for a memorised answer.
c+r
Why it's wrong here
'c' is not a valid category (u, g, o, a are valid).
g-w
Why this is correct
Removes write permission for the group.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates may confuse numeric (octal) modes with symbolic modes, or assume that any single-letter class like 'c' is valid, when only u, g, o, and a are recognized by the chmod command.
Detailed technical explanation
Symbolic modes in chmod are defined by POSIX (IEEE Std 1003.1) and consist of a combination of references (u/g/o/a), operators (+/-/=), and permissions (r/w/x/X/s/t). The 'a' class is shorthand for 'ugo', so 'a+rwx' adds read, write, and execute for all three classes simultaneously. Under the hood, chmod parses the symbolic string and applies bitwise operations to the file's mode bits stored in the inode.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LPIC-1 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
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FAQ
GNU and Unix Commands — This question tests GNU and Unix Commands — Read the scenario before looking for a memorised answer..
The correct answer is: u+x — Option A is correct because 'u+x' is a valid symbolic mode expression for chmod, where 'u' stands for the user (owner), '+' adds a permission, and 'x' is the execute permission. This syntax follows the POSIX standard for symbolic modes, allowing precise modification of file permissions without specifying an absolute octal value.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This LPIC-1 practice question is part of Courseiva's free LPI 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 LPIC-1 exam.
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