How to use
- Toggle permission checkboxes for read (4), write (2), and execute (1) across owner, group, and others.
- Or type an octal number like 755 or 644 to instantly calculate the corresponding symbolic string.
- Copy the generated terminal command (with recursive -R flag if modifying an entire folder).
FAQ
How are octal chmod values calculated?
Each permission has a numerical value: Read = 4, Write = 2, Execute = 1. Summing these values yields a single digit (0 through 7) for each entity: Owner, Group, and Others.
Why is chmod 777 hazardous in production?
Permission 777 grants full unrestricted write and execute authority to all system accounts. For public websites, standard secure permissions are 644 for files and 755 for directories.
What permissions should SSH keys have?
Private SSH key files (~/.ssh/id_rsa) require strict 600 permissions (read and write only by the owner). SSH clients intentionally reject keys with broader permissions.