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SSCP Practice Question: Which two commands can be used to modify existing…
Which two commands can be used to modify existing file permissions on a Linux system? (Select TWO)
⚠ Common exam trap
ISC2 often tests the distinction between commands that modify existing permissions (`chmod`, `setfacl`) versus commands that set defaults for new files (`umask`) or change file ownership (`chown`), leading candidates to mistakenly select `umask` or `chown` as tools for altering current 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
✓
setfacl
Option B, setfacl, is correct because it modifies existing file permissions by adding, modifying, or removing POSIX ACL entries (e.g., setfacl -m u:alice:rw file), which directly changes the access permissions on a file. Option E, chmod, is correct because it changes the existing permission bits (read/write/execute for user, group, and other) of a file or directory, for example chmod 640 file or chmod u+x file. Option A, chattr, does not set standard permissions; it changes extended filesystem attributes such as immutable (+i) or append-only (+a), so it is not a permission-modifying command in this sense. Option C, umask, does not modify existing file permissions; it sets the default permission mask applied only when new files and directories are created. Option D, chown, changes file ownership (user and/or group), not the permission bits themselves, so it does not modify existing permissions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
chattr
Why it's wrong here
chattr alters extended file attributes such as immutable or append-only flags, not the read/write/execute permission bits. chmod is the command that changes those mode bits. chattr is correct when hardening files against modification or deletion, for example setting the immutable flag.
- ✓
setfacl
Why this is correct
`setfacl` modifies access control lists, granting or revoking per-user and per-group permissions beyond the standard owner/group/other model. This satisfies the stem's requirement to modify existing file permissions, since ACL entries can be added, altered, or removed on files that already exist, without changing their base mode bits.
- ✗
umask
Why it's wrong here
umask sets the default permission mask applied to newly created files and directories; it cannot change permissions on files that already exist. chmod modifies existing mode bits. umask is the correct command when controlling the permissions inherited by future files.
- ✗
chown
Why it's wrong here
chown changes file ownership (user and group), not the permission bits themselves. chmod is the command that modifies existing read/write/execute permissions. chown is correct when transferring ownership, such as reassigning files to a different service account.
- ✓
chmod
Why this is correct
`chmod` directly alters the permission bits (read, write, execute) for owner, group and others on existing files, satisfying the stem's requirement to modify permissions. It operates on the mode field of the inode, unlike `chown` (ownership) or `umask` (defaults for new files), making it a valid selection.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SSCP practice question is part of Courseiva's free ISC2 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 SSCP exam.