How do you read a Linux permission mode?
-rwxr-x--- splits into owner, group and other. The owner has read/write/execute; the group has read/execute; everyone else has no access.
Core commands
chmod 640 report.txt chown alice:admins report.txt chgrp admins report.txt umask 027 ls -l report.txt stat report.txt
Numeric modes
| Mode | Meaning |
|---|---|
| 600 | Owner read/write only |
| 640 | Owner read/write; group read |
| 700 | Owner full access only |
| 755 | Owner full; group/other read+execute |
Special bits
- Sticky bit: useful on shared directories such as
/tmp. - setgid on a directory: new files can inherit the directory's group.
- setuid: affects execution identity on appropriate executable files; treat it carefully from a security perspective.
Practice task
Create a shared directory for a group, set group ownership, make new files inherit the group, and prevent users outside the group from entering. Then verify with a second user account.
Frequently asked questions
What should you practice first?
Permissions become useful when you can predict the result, apply the change and verify it.
Does this guide replace the official certification objectives?
No. Use this guide as practice support and keep the current issuer objectives or competencies beside your lab notes so your preparation stays aligned with the live exam.
How do you know the practice worked?
Verify the resulting system state with an independent command, log, service check or repeatable test instead of assuming a command succeeded because it returned no error.