Re: Shred: Add recursion operations [PATCH]

[Amr Ali]

On 12/10/2011 12:11 AM, Bob Proulx wrote:
> Pádraig Brady wrote:
>> Eric Blake wrote:
>>> Amr Ali wrote:
>>>> I'm not sure if this was discussed before, but I've got tired
>>>> from having to work around the lack of native recursion within
>>>> `shred`. So, attached is a patch to add recursion, including
>>>> documentation.
>>>
>>> Thanks for taking the effort to write a patch, but we probably won't
>>> accept this upstream.
>>
>> I agree.
>> Also not that shred is of limited use with files,
>> given that the info is probably spread elsewhere on
>> the disk from moving files around, and temp files,
>> and slop at the end of blocks, ...
> 
> I think perhaps that stronger warnings should be added to the
> documentation that shred isn't appropriate for files on modern
> journaling filesystems.  The very presence of shred leads people to
> believe that it performs strong magic that it can't actually do.  Some
> so much that they will submit patches (highly commendable btw, if
> misguided in this particular case) to make it operate even more on
> files.  We should be discouraging the use of shred on files rather
> than encouraging it.
I never implied that I think shred performs "strong magic". But if you mean by
"strong magic" the effects of layered overwriting with pseudo-random data on the
disc magnetic polarity differences and how journaled file systems act as a
diffuser in the shredding process which effectively evaporates the implied
result of shredding, then yes. And it's not the drive behind my patch 
submission.

And the fact that it doesn't result into the desired effect on journaled file
systems does not necessarily result into subtly discontinuing it's usage on
*all* other _file_ systems. They are not mutually exclusive.

My issue is more targeted towards usability, and I do in fact utilize shred on
old non-journaled file systems, that could be really my only usage of it.

> 
>   http://stackoverflow.com/questions/913282/shred-doesnt-work-on-journaled-fs
> 
> Bob

-- 
Amr Ali

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