best fedora solution to securely erase folders/clean free space?

[M. Fioretti]

On Sat, Mar 30, 2013 13:41:20 PM +0100, Reindl Harald wrote:

> if you have a virtual machine with growable disks and delete a lot of
> data the disk will not get smaller, shrink the disk will not really work
> 
> after write zeros to the free space in the guest you can successful
> shrink the virtual disk on the host system

ok, now I get what you meant, thanks.

And I also realize I forgot a part in my initial question: how to do
the same thing with the swap partition? Would this technique still
work or make the system unusable? (as I said, what I'm looking at is
how to clean a live, running system, hence the question)

Marco