Quick Answer
The answer is /etc/cron.deny. This file explicitly lists users who are denied permission to schedule cron jobs, so adding 'john' to it will prevent him from using the crontab command. The system checks /etc/cron.deny only when /etc/cron.allow does not exist; if /etc/cron.allow is present, only users listed there may use cron, and /etc/cron.deny is ignored. On the LPIC-1 exam, this concept tests your understanding of the cron access control hierarchy, often appearing in questions that contrast allow and deny files. A common trap is assuming /etc/cron.deny is checked first, but the actual priority is: /etc/cron.allow takes precedence, then /etc/cron.deny, and if neither exists, only root can schedule jobs. A helpful memory tip is "Deny is the default blocklist, Allow is the exclusive whitelist."
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.
An administrator wants to prevent a specific user, 'john', from being able to schedule cron jobs. Which file should the administrator modify?
/var/spool/cron/crontabs
Why wrong: Directory containing user crontab files; removing john's file would not prevent re-creation.
/etc/cron.allow
Why wrong: If this file exists, only listed users can use cron; adding john would allow him.
/etc/crontab
Why wrong: System-wide crontab, not for user restrictions.
/etc/cron.deny
Add 'john' to this file to prevent him from using cron.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
/etc/cron.deny
The /etc/cron.deny file lists users who are explicitly denied access to schedule cron jobs. If this file exists and the user 'john' is listed in it, he will be prevented from using crontab. This is the standard mechanism for restricting cron access when /etc/cron.allow does not exist.
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.
/var/spool/cron/crontabs
Why it's wrong here
Directory containing user crontab files; removing john's file would not prevent re-creation.
/etc/cron.allow
Why it's wrong here
If this file exists, only listed users can use cron; adding john would allow him.
/etc/crontab
Why it's wrong here
System-wide crontab, not for user restrictions.
/etc/cron.deny
Why this is correct
Add 'john' to this file to prevent him from using cron.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse /etc/cron.allow with /etc/cron.deny, thinking that modifying the allow file is the only way to control access, but the question specifically asks for a file to prevent a user, which is the deny file.
Detailed technical explanation
Under the hood, cron access control is checked by the crontab command: if /etc/cron.allow exists, only users listed there can use crontab; otherwise, if /etc/cron.deny exists, users listed there are denied. If neither file exists, on many Linux distributions, only root can schedule cron jobs. A real-world scenario is a shared server where an administrator wants to restrict a specific user without affecting others, making /etc/cron.deny the precise tool.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Administrative Tasks — This question tests Administrative Tasks — Read the scenario before looking for a memorised answer..
The correct answer is: /etc/cron.deny — The /etc/cron.deny file lists users who are explicitly denied access to schedule cron jobs. If this file exists and the user 'john' is listed in it, he will be prevented from using crontab. This is the standard mechanism for restricting cron access when /etc/cron.allow does not exist.
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 11, 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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