Subject: Re: securely erasing a hard disk
To: None <>
From: Philip Jensen <>
List: tech-security
Date: 10/21/2005 15:03:46
On 10/21/05, Thor Lancelot Simon <> wrote:
> On Fri, Oct 21, 2005 at 01:35:24PM +1300, Philip Jensen wrote:
> >
> > If so, then does the -P switch for the NetBSD rm command really
> > provide the "security" of data erasure people think they are getting?
> > Or should the man page have an addition of "If you are serious about
> > removing all traces of this file then ......."?
> Did you read the entire manual page?  The -P option is the subject of
> extensive text in the BUGS section

     The -P option assumes that the underlying file system is a fixed-block
     file system.  UFS is a fixed-block file system, LFS is not.  In additi=
     only regular files are overwritten, other types of files are not.

But it doesn't talk about the validity of the process for removing a
file.  More specifically whether you should do something else if you
want to be more sure of erasing the file's contents.

> and a rather lengthy warning in the

     The rm utility differs from historical implementations in that the -f =
     tion only masks attempts to remove non-existent files instead of maski=
     a large variety of errors.

     Also, historical BSD implementations prompted on the standard output, =
     the standard error output.

-P is not mentioned in compatibility at all.

> I don't think we could really be much more
> specific about it than we already are.
> Thor