Re: [coreutils] [PATCH] doc: show how to shred using a single zero-writing pass

[Pádraig Brady]

On 17/01/11 10:36, Jim Meyering wrote:
>>From 7dc6335653afcdad9a3ffa327877571734644285 Mon Sep 17 00:00:00 2001
> From: Jim Meyering <address@hidden>
> Date: Mon, 17 Jan 2011 11:32:35 +0100
> Subject: [PATCH] doc: show how to shred using a single zero-writing pass
> 
> * doc/coreutils.texi (shred invocation): Give an example showing how
> to invoke shred in its most basic (fastest) write-only-zeros mode.
> ---
>  doc/coreutils.texi |    9 +++++++++
>  1 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/doc/coreutils.texi b/doc/coreutils.texi
> index 9c3e2ed..8fb9f0c 100644
> --- a/doc/coreutils.texi
> +++ b/doc/coreutils.texi
> @@ -8892,6 +8892,15 @@ shred invocation
>  shred --verbose /dev/sda5
>  @end example
> 
> +On modern disks, a single pass that writes only zeros may be enough,
> +and it will be much faster than the default.

Well only 3 times, due to the disk being the bottleneck
(since we changed to the fast internal PRNG by default).
Also for security, writing random data would probably be more effective.
So I'd reword the above sentence to:

"To simply clear a disk"

> +Use a command like this to tell @command{shred} to skip all random
> +passes and to perform only a final zero-writing pass:
> +
> +@example
> +shred --verbose -n0 --zero /dev/sda5
> +@end example

It's probably not worth noting the equivalent:
dd conv=fdatasync bs=2M < /dev/zero > /dev/sda5

cheers,
Pádraig.