You can specify optional, additional permission restrictions on the path using traditional UNIX notation. For example, “u+rw” gives the user read-write access, the group read-only access, and all others are denied access. These restrictions do not affect operating system permissions; a user who allowed read-write access in the configuration statement does not gain write access to a directory that has read-only operating system permissions.
When a mask is not provided, the default mask of 0666 is used for the directory for all write operations including file creation. The mask is not used for read-only operations.
When a mask is provided, a default mask of all zeroes is assumed. This ensures that a mask specified as (u+rw) results in a mask of 0600.
