easyMultiple ChoiceObjective-mapped
XK0-006 Practice Question: A system administrator is tasked with ensuring…
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?
⚠ Common exam trap
Many candidates 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.
Answer choices
Why each option matters
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.
Answer analysis
Option-by-option breakdown
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
Applying an ACL fails because it extends standard permissions for specific users or groups, but does not alter the fundamental behaviour of directory write permissions that typically allow any user with write access to delete files within it, regardless of file ownership. ACLs are tempting as they provide fine-grained control, allowing administrators to grant or deny specific access levels to individual users or multiple groups on a file or directory, which standard Unix permissions cannot achieve. They are the correct choice for complex access requirements beyond owner, group, and other.
- ✓
Set the sticky bit
Why this is correct
The sticky bit prevents users from deleting files they do not own in the directory.
- ✗
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.
Go deeper
Related to this question
Learn chapter
File Permissions and Ownership
Key term
Sticky bit
The sticky bit is a special permission on Unix/Linux files and directories that restricts file deletion to the file owner, directory owner, or root user, even if others have write access.
Key term
chmod
chmod is a command in Linux and Unix-like operating systems used to change the permissions (read, write, execute) of a file or directory.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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