how to overwrite the content of a file

[Wojciech Puchar]

dd if=/dev/zero of=file seek=x count=y bs=z conv=notrunc

will overwrite y blocks of z size beginning from block x

On Thu, 11 Nov 2010, Matthias Apitz wrote:

>
> Hello,
>
> What is the best method to overwrite the blocks of a given file with
> bytes of 0x00, i.e. not to O_TRUNC away the blocks to the freelist of the
> file system, but overwrite the old blocks?
>
> I've checked
>
> $ dd if=/dev/zero of=file count=4
>
> but dd(1) opens the file with O_RDWR|O_CREAT|O_TRUNC which for sure will
> give away the old blocks and adquire new blocks. Any idea?
>
> The background of the question is that I want to make sure, that certain
> content is not placed into a dump of the file system before give away
> the output of the dump(8).
>
> Thanks
>
> 	matthias
> -- 
> Matthias Apitz
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