This XK0-005 practice question tests your understanding of security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 system administrator is tasked with ensuring that users cannot delete files owned by other users in a shared directory. Which permission should be set on the directory?
Apply an ACL
Why wrong: An ACL can restrict delete access, but the sticky bit is the standard, simpler solution.
Set the sticky bit
The sticky bit prevents users from deleting files they do not own in the directory.
Set the SGID bit
Why wrong: SGID causes new files to inherit the directory's group, but does not prevent deletion.
Set the SUID bit
Why wrong: SUID affects execution privileges, not file deletion.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Set the sticky bit
The sticky bit (chmod +t) on a directory restricts deletion so that only the file owner, the directory owner, or root can remove files, even if the directory has world-writable permissions. This directly prevents users from deleting files owned by others in a shared directory, which is the requirement.
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.
Apply an ACL
Why it's wrong here
An ACL can restrict delete access, but the sticky bit is the standard, simpler solution.
Set the sticky bit
Why this is correct
The sticky bit prevents users from deleting files they do not own in the directory.
Related concept
Read the scenario before looking for a memorised answer.
Set the SGID bit
Why it's wrong here
SGID causes new files to inherit the directory's group, but does not prevent deletion.
Set the SUID bit
Why it's wrong here
SUID affects execution privileges, not file deletion.
Common exam traps
The trap here is that candidates often confuse the sticky bit with SUID or SGID, or think an ACL is required, but the sticky bit is the exact POSIX mechanism designed for shared directory deletion control.
Detailed technical explanation
The sticky bit is defined in POSIX and is set using chmod +t or octal mode 1000. When applied to a directory, it modifies the behavior of the unlink() and rename() system calls: the kernel checks if the calling process owns the file or the directory, or has CAP_FOWNER (root), before allowing deletion. This is commonly used on /tmp (mode 1777) to prevent users from deleting each other's temporary files.
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.
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FAQ
Security — This question tests Security — Read the scenario before looking for a memorised answer..
The correct answer is: Set the sticky bit — The sticky bit (chmod +t) on a directory restricts deletion so that only the file owner, the directory owner, or root can remove files, even if the directory has world-writable permissions. This directly prevents users from deleting files owned by others in a shared directory, which is the requirement.
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 XK0-005 practice question is part of Courseiva's free CompTIA 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 XK0-005 exam.
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