When designing Wrapfs, we concentrated on the following aspects:
The first four points are discussed below. Performance is
addressed in detail in Section 5. Without changing a given Vnode
interface, we have identified three items that file system
developers want to inspect or manipulate: file data, names, and
attributes. Changing file data is the most obvious (e.g.,
encryption). Changing file names as part of, say, encryption is
also desired. For example, a file system may refuse to create
files that contain rarely used characters such as whitespace and
other non-printable characters, or visually confusing names such
as ``...'' (three dots) as these are sometimes used by intruders
to obscure their tracks. More advanced use can be made by
inspecting file names and selectively manipulating them. For
example, a file system that adds immutable file support will
need to have a list of file names to consider untouchable.
Several file systems can place auxiliary information (such as
access keys) in files that are hi