u – users g – groups o – others
- chmod +rwx filename to add permissions to users,groups,others.
- chmod -rwx filename to remove permissions.
- chmod +x filename to allow executable permissions
- chmod u+x filename to allow executable permissions for user
- chgrp groupname filename
- chgrp groupname foldername
- chown username filename
- chown username foldername
https://www.pluralsight.com/blog/it-ops/linux-file-permissions