Re: secure erasure of files?

[Helge Hafting <helgehaf@aitel.hist.no>]

Andreas Ferber wrote:

> I don't know if any filesystem currently relocates blocks if you
> overwrite a file, but it's certainly possible and allowed (everything
> else except the filesystem itself simply must not care where the data
> actually ends up on the disk).
> 
A log-structured fs will write new blocks everytime, afaik.
Ext3 with data journalling keeps copies of recently written data
in the journal.  Now, if you create a "secret" file and then overwrite
it you'll still find a copy in the journal until the journal wraps
It may not wrap if the next thing you do is umount/shutdown.

A secure rm must know the fs it works with.  A better solution
is to overwrite the entire partition with garbage. The only
perfect way is to destroy the magnetic surfaces though.


Helge Hafting