Chmod Cheatsheet

File permissions in Linux control who can read, write, or execute files. The chmod command modifies these permissions using either symbolic notation (letters) or octal notation (numbers).

File ownership is a crucial aspect of Linux/Unix permissions. Every file and directory has an owner and a group assignment that, together with the file permissions, determine who can access or modify it.

Special permissions extend the basic read/write/execute model with additional capabilities that affect how files are executed and directories are managed. These permissions enable powerful behaviors like executing programs with owner privileges and controlling directory write access.

Permission operations allow you to modify file and directory permissions without having to specify the complete permission set. These operations provide flexibility to add, remove, or set exact permissions while preserving existing ones when needed.

Advanced chmod techniques allow for more sophisticated permission management, including reference-based permissions, conditional changes, umask configuration, and integration with Access Control Lists (ACLs) for fine-grained access control.