Permissions & Security (Chmod/Chown/ACLs/SELinux/AppArmor)

Precision Access Control with Linux ACLs

🧩 The Challenge

Traditional Unix permissions only allow for a single owner, single group, and others, making it impossible to grant read access to a specific user without changing group ownership.

💡 The Fix

Use Access Control Lists to define granular permissions for multiple specific users or groups on a single file or directory.

setfacl -m u:username:r file.txt
getfacl file.txt

⚙️ Why It Works

The setfacl command modifies the extended attributes of the filesystem object, allowing the kernel to check access against a custom list rather than just the basic mode bits.

🚀 Pro-Tip: Use getfacl -R directory | setfacl -b -M – target_directory to replicate existing complex permissions across a new folder structure.

Linux Tips & Tricks | © ngelinux.com | 7/5/2026