Lion Cipher Lab
Users and permissions on Linux: least privilege in practice
- Cyber / Security Engineer
- Beginner
- ~45 min
- Free · no account required
Why it matters
Almost every Linux security control comes back to one question: who is allowed to do what? Running everything as the all-powerful root user is the single most common way a small mistake or a single compromised program turns into a full system takeover. Learning to create a normal user, grant only the access it needs, and read and set file permissions is the everyday, defensive skill behind hardening a server, passing an audit, and limiting the blast radius when something goes wrong.
What you'll learn
- Linux users & groups
- sudo & root
- reading file permissions (rwx)
- chmod & chown
- least privilege
Steps in this lab
- Who are you right now? (whoami, id, and the idea of root)
- Borrow power for one command, not forever (sudo)
- Create a normal user the way admins do (adduser / useradd)
- Read a permission line like a security pro (ls -l)
- Change permissions safely, and give the minimum (chmod)
- Change ownership deliberately (chown) — and see a denial happen
- Clean up, and why this is the job (deluser)
- The mindset to carry forward