What is umask and how is it determined on a Linux system?

umask sets the mask applied to newly created file and directory permissions. For directories, the base permissions are (rwxrwxrwx) and for files they are 666 (rw-rw-rw).

Before creating the file or directory, the base permissions are compared to a mask (the umask set by the umask command or default mask as applicable) that will "mask out" permission bits to determine the final permissio...