misc/65494: dd bs size _MUST_ be N*512 - bug or feature

[Kris Kennaway]

The following reply was made to PR misc/65494; it has been noted by GNATS.

From: Kris Kennaway <kris at obsecurity.org>
To: Sheshka Alexey <pulsar at sky-zebra.net>
Cc: freebsd-gnats-submit at FreeBSD.org
Subject: Re: misc/65494: dd bs size _MUST_ be N*512 - bug or feature
Date: Fri, 16 Apr 2004 01:49:29 -0700

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 On Tue, Apr 13, 2004 at 09:07:45AM -0700, Sheshka Alexey wrote:
 
 > While I'm making=20
 > root at service.extmedia.com [~] # dd if=3D/dev/ad0 of=3D/dev/null bs=3D1000=
  count=3D10
 > dd: /dev/ad0: Invalid argument
 > 0+0 records in
 > 0+0 records out
 > 0 bytes transferred in 0.000544 secs (0 bytes/sec)
 > it produse error, but
 > root at service.extmedia.com [~] # dd if=3D/dev/ad0 of=3D/dev/null bs=3D4096=
  count=3D10
 > 10+0 records in
 > 10+0 records out
 > 40960 bytes transferred in 0.013014 secs (3147361 bytes/sec)
 > all good.
 >=20
 > On OpenBSD and Linux all woks fine with _ANY_ value of bs ... Is it bug o=
 r feature in FreeBSD ?
 > If it is feature , I think this information must presents on it.
 > >How-To-Repeat:
 >       dd if=3D/dev/ad0 of=3D/dev/null bs=3D1000 count=3D10
 
 Feature, I think - you have to use a multiple of the block size of the
 underlying device, because FreeBSD no longer implements buffered
 devices.
 
 Kris
 
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