This LFCS practice question tests your understanding of user and group management. 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.
Exhibit
Refer to the exhibit.
# useradd -u 1005 -G wheel,dbadmin -m -k /etc/skel newuser
useradd: user 'newuser' already exists
#
Refer to the exhibit. The administrator attempted to create a user 'newuser' but received an error. Which command should be used to check if the user already exists?
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.
Exhibit
Refer to the exhibit.
# useradd -u 1005 -G wheel,dbadmin -m -k /etc/skel newuser
useradd: user 'newuser' already exists
#
A
cat /etc/passwd | grep newuser
Correct. The /etc/passwd file stores all user account information. Using cat and grep to search for the username is a reliable method to verify if the user exists.
B
passwd -S newuser
Why wrong: Incorrect. The passwd -S command shows the password status of an existing user. If the user does not exist, it will return an error; it is not used for existence verification.
C
usermod -c newuser
Why wrong: Incorrect. The usermod -c command modifies the user's comment field and assumes the user already exists. It cannot be used to check if a user exists.
D
userdel -v newuser
Why wrong: Incorrect. The userdel -v command deletes a user and will fail if the user does not exist. It is not appropriate for checking user existence.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
cat /etc/passwd | grep newuser
Option A is correct because the /etc/passwd file stores all user account information, and using cat to pipe its contents through grep allows the administrator to search for the specific username 'newuser'. If the user exists, grep will output the matching line; if not, no output is returned. This is a standard, quick method to verify user existence without modifying system state.
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.
✓
cat /etc/passwd | grep newuser
Why this is correct
Correct. The /etc/passwd file stores all user account information. Using cat and grep to search for the username is a reliable method to verify if the user exists.
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.
✗
passwd -S newuser
Why it's wrong here
Incorrect. The passwd -S command shows the password status of an existing user. If the user does not exist, it will return an error; it is not used for existence verification.
✗
usermod -c newuser
Why it's wrong here
Incorrect. The usermod -c command modifies the user's comment field and assumes the user already exists. It cannot be used to check if a user exists.
✗
userdel -v newuser
Why it's wrong here
Incorrect. The userdel -v command deletes a user and will fail if the user does not exist. It is not appropriate for checking user existence.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose a command that seems related to user management (like passwd or usermod) without realizing those commands assume the user already exists and will produce errors or unintended side effects when used for existence verification.
Trap categories for this question
Command / output trap
Incorrect. The passwd -S command shows the password status of an existing user. If the user does not exist, it will return an error; it is not used for existence verification.
Detailed technical explanation
How to think about this question
The /etc/passwd file is a colon-delimited text database containing seven fields per user: username, password placeholder (x), UID, GID, GECOS comment, home directory, and login shell. Using grep to search this file is efficient because it reads directly from the filesystem without invoking any user management daemons, and it works even if the system is in single-user mode or if NSS (Name Service Switch) is configured to use local files first. In real-world scenarios, administrators often combine this with 'getent passwd newuser' to query all configured name services (e.g., LDAP, NIS) for a more comprehensive check.
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.
User and Group Management — This question tests User and Group Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: cat /etc/passwd | grep newuser — Option A is correct because the /etc/passwd file stores all user account information, and using cat to pipe its contents through grep allows the administrator to search for the specific username 'newuser'. If the user exists, grep will output the matching line; if not, no output is returned. This is a standard, quick method to verify user existence without modifying system state.
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: "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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