This XK0-005 practice question tests your understanding of system management. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 company policy requires that only the root user can schedule cron jobs. Which configuration ensures this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create /etc/cron.allow with only 'root'
Option D is correct because /etc/cron.allow lists users allowed to use crontab; if it exists and contains only root, then only root can use crontab. Option A is wrong because /etc/crontab is for system-wide cron jobs, not user access control. Option B is wrong because modifying permissions on /usr/bin/crontab could break the binary. Option C is wrong because /etc/cron.deny blocks users but if it contains all users except root, it's impractical; the standard approach is to use cron.allow.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Create /etc/cron.allow with only 'root'
Why this is correct
If /etc/cron.allow exists, only users listed can use crontab. Listing only root restricts it to root.
Related concept
Standard ACLs match source addresses.
✗
Add 'root' to /etc/crontab
Why it's wrong here
/etc/crontab is for system cron jobs, not user access control.
✗
Set /usr/bin/crontab permissions to 700
Why it's wrong here
Changing permissions on the binary could break functionality for root as well.
✗
Add all non-root users to /etc/cron.deny
Why it's wrong here
This is cumbersome and not the standard method; cron.allow is simpler.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related XK0-005 ACL questions on filtering logic and placement.
System Management — This question tests System Management — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Create /etc/cron.allow with only 'root' — Option D is correct because /etc/cron.allow lists users allowed to use crontab; if it exists and contains only root, then only root can use crontab. Option A is wrong because /etc/crontab is for system-wide cron jobs, not user access control. Option B is wrong because modifying permissions on /usr/bin/crontab could break the binary. Option C is wrong because /etc/cron.deny blocks users but if it contains all users except root, it's impractical; the standard approach is to use cron.allow.
What should I do if I get this XK0-005 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related XK0-005 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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