XK0-006 System Management Practice Question
A Linux administrator needs to add an ACL entry to grant read permission to a user named 'jdoe' on a file. Which TWO commands can be used to achieve this? (Select TWO).
⚠ Common exam trap
The trap is confusing ACL modification with ownership change (chown) or standard permission change (chmod), and failing to recognize that -m and --modify are equivalent long/short options for setfacl.
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
✓
setfacl -m u:jdoe:r file
Option A, `setfacl -m u:jdoe:r file`, is correct because `-m` is the short form of `--modify`, and `u:jdoe:r` adds or modifies an ACL entry granting user jdoe read permission on the file. Option B, `setfacl --modify u:jdoe:r file`, is correct because it is the long-form equivalent of the same command, performing the identical ACL modification. Option C, `chown jdoe file`, only changes the file's owner and does not create an ACL entry, so it does not grant read permission via ACL. Option D, `setfacl -x u:jdoe file`, removes an existing ACL entry for jdoe rather than adding one. Option E, `chmod u+r file`, modifies the standard Unix permission bits for the file's owner, not an ACL entry for jdoe.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
setfacl -m u:jdoe:r file
Why this is correct
setfacl -m invokes modify mode, and the entry u:jdoe:r adds an ACL granting user jdoe read permission on the file without altering the existing owner, group or other bits. This directly satisfies the requirement to add a read ACL entry for that named user.
- ✓
setfacl --modify u:jdoe:r file
Why this is correct
setfacl --modify is the long-form equivalent of -m, and u:jdoe:r specifies a user entry granting jdoe read access. It adds the ACL entry to the file's access ACL, satisfying the requirement identically to the short-option form.
- ✗
chown jdoe file
Why it's wrong here
chown changes file ownership, not the ACL entry list, so it cannot grant jdoe read permission while leaving the existing owner intact. It is tempting because ownership and permissions are closely related, and chown is correct when the requirement is transferring a file to a different user or group.
- ✗
setfacl -x u:jdoe file
Why it's wrong here
The -x flag removes an existing ACL entry rather than adding one, so no read permission is granted to jdoe. It is tempting because setfacl is the correct tool family, and -m u:jdoe:r would add the entry this scenario requires.
- ✗
chmod u+r file
Why it's wrong here
chmod u+r alters only the file's owning-user permission bits, so it cannot create a named-user ACL entry for jdoe. It is tempting because chmod does manipulate permissions, and setfacl -m u:jdoe:r is the actual command that adds the ACL entry.
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Related to this question
Learn chapter
Installing Linux and Package Management
Key term
ACL
An Access Control List is a set of rules that determines who or what can access specific network resources or data.
Key term
Linux
Linux is an open-source operating system that manages computer hardware and software, widely used in servers, desktops, and embedded systems.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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