Permissions

Permissions: Permissions: Read, Write and Run, sudo and Who Owns a File.

Updated November 10, 2026

1. Permissions: Read, Write and Run (Apprentice): Every file says who may read it, change it and run it, for its owner, its group and everyone else; ls -l shows it as letters such as rwxr-xr-x, chmod +x lets a program run, and chmod 644 or 600 sets all nine at once with numbers.
2. sudo and Who Owns a File (Journeyman): Every file has an owner and a group, and only root, the computer's administrator account, may change anything; sudo runs one command as root after asking for your password, and chown gives a file a new owner, so both are used rarely and on purpose.