XK0-006 System Management Practice Question
A file has permissions rwxr-x--- and is owned by user alice and group devs. Which command would add the SUID bit while preserving existing permissions?
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
✓
chmod u+s file
chmod u+s adds the SUID bit. The symbolic mode 'u+s' sets the SUID without changing the existing permission bits.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
chmod a+s file
Why it's wrong here
chmod a+s file sets the SUID and SGID bits (and sticky bit for others), altering more than just the SUID bit and not preserving existing permissions correctly.
- ✓
chmod u+s file
Why this is correct
chmod u+s file correctly adds only the SUID bit for the owner without changing any other permissions, preserving the existing rwxr-x---.
- ✗
chmod 2755 file
Why it's wrong here
chmod 2755 file sets the SGID bit and changes permissions to rwxr-xr-x, which does not preserve the existing permissions and adds SGID instead of SUID.
- ✗
chmod 4750 file
Why it's wrong here
chmod 4750 file sets the SUID bit and explicitly sets permissions to 750, which matches the current permissions; however, using numeric mode risks altering permissions if the current value is unknown, making symbolic mode the preferred method.
Go deeper
Related to this question
Learn chapter
File Permissions and Ownership
Key term
User
A user is any person, system, or device that interacts with an IT service, resource, or identity system, typically authenticated through credentials and authorized to perform specific actions.
Key term
SUID
SUID (Set User ID) is a special file permission in Linux that allows a user to run an executable file with the file owner's privileges, typically root, rather than their own.
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Written by Johnson Ajibi, MSc IT Security
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