This LPIC-1 practice question tests your understanding of administrative tasks. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 user 'jdoe' already exists. The administrator needs to add 'jdoe' to the 'staff' and 'admin' groups without changing other group memberships. Which command accomplishes this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
usermod -a -G staff,admin jdoe
Option A is correct because the `usermod -a -G` command appends the user 'jdoe' to the supplementary groups 'staff' and 'admin' without altering existing group memberships. The `-a` (append) flag is essential; without it, `-G` would replace all current supplementary groups with only those listed. This matches the requirement to add the user to new groups while preserving other group memberships.
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.
✓
usermod -a -G staff,admin jdoe
Why this is correct
The -a (append) flag with -G adds the user to the listed groups without affecting other group memberships.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
sed -i 's/^staff:.*/&jdoe/' /etc/group
Why it's wrong here
Directly editing /etc/group is error-prone and not recommended; use usermod instead.
✗
usermod -G staff,admin jdoe
Why it's wrong here
Without -a, this overwrites the user's supplementary group list, removing existing groups.
✗
useradd -G staff,admin jdoe
Why it's wrong here
useradd is for creating new users; for existing users, usermod should be used.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often forget the `-a` (append) flag with `usermod -G`, assuming `-G` alone adds groups, when in fact it replaces all supplementary group memberships, which is a common cause of accidental privilege removal.
Detailed technical explanation
How to think about this question
Under the hood, `usermod` modifies the `/etc/group` and `/etc/gshadow` files to update group memberships. The `-a` flag ensures the new groups are appended to the existing list in the `GID` field of the user's entry in `/etc/passwd` and the corresponding group lines. A common real-world scenario is when an administrator needs to grant additional permissions (e.g., sudo via 'admin' group or file access via 'staff') without disrupting existing access, such as membership in 'docker' or 'wheel' groups. Without `-a`, a simple oversight can lock the user out of critical resources.
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 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
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.
Administrative Tasks — This question tests Administrative Tasks — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: usermod -a -G staff,admin jdoe — Option A is correct because the `usermod -a -G` command appends the user 'jdoe' to the supplementary groups 'staff' and 'admin' without altering existing group memberships. The `-a` (append) flag is essential; without it, `-G` would replace all current supplementary groups with only those listed. This matches the requirement to add the user to new groups while preserving other group memberships.
What should I do if I get this LPIC-1 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: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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