This is a good question, actually, each filesystem has its own rules for slack space. Let's consider UFS or ext3, as they act the same in this meaning :
Quote:
|
By default, sparse SOURCE files are detected by a crude heuristic and the corresponding DEST file is made sparse as well. That is the behavior selected by --sparse=auto. Specify --sparse=always to create a sparse DEST file whenever the SOURCE file contains a long enough sequence of zero bytes. Use --sparse=never to inhibit creation of sparse files.
|
where sparse files are a type of computer files that attempt to use file system space more efficiently; so, "cp" by default doesn't use slack space, means , it's optimized for work.
