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

Granting Granular File Access with POSIX Access Control Lists

🧩 The Challenge

Standard Linux permissions only allow setting rights for a single owner, a single group, and others, making it impossible to grant specific access to multiple users without creating messy custom groups.

💡 The Fix

Use POSIX Access Control Lists to define individual permissions for specific users or groups on a file or directory without altering standard ownership.

setfacl -m u:username:rw /path/to/file
getfacl /path/to/file

⚙️ Why It Works

The setfacl command modifies the extended attribute set of the inode, allowing the kernel to check against a secondary list of access rules before denying or granting requests.

🚀 Pro-Tip: Use the -R flag with setfacl to apply these specific user permissions recursively across an entire directory tree.

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