Mailinglist Archive: opensuse (1438 mails)

[Anders Johansson <ajohansson@xxxxxxx>]

On Wednesday 06 May 2009 00:33:48 Greg Freemyer wrote:
> All,
>
> I am a heavy user of dd and think I know it well, but we had some
> unexpected behavior out of dd recently.  At least it was unexpected by
> us.
>
> In its simplest reproducible form we did something like:
>
> md5sum big_file
>
> cat big_file | dd bs=32k conv=sync,noerror | md5sum
[...]
> Anyway, I don't know if the above is by design, or if we have come
> across a bug.  If a bug, is it in dd?  the kernel?

You really don't want to use conv=sync here. noerror is fine, but sync is not. 
With noerror, dd will continue, and try its best to fill up the output buffer. 
With sync, it will bad the output buffer with zeros, which will do nasty 
things to your md5sum.

Anders
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