The chmod Linux and Unix command experts ;) If you don't know any better, see my pages:

→ Chmod Numeric Permissions Notation Linux / Unix https://www.cyberciti.biz/faq/unix-linux-bsd-chmod-numeric-permissions-notation-command/

→How To Use chmod and chown Command in Linux https://www.cyberciti.biz/faq/how-to-use-chmod-and-chown-command/