From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754351AbZEWTUU (ORCPT ); Sat, 23 May 2009 15:20:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752285AbZEWTUK (ORCPT ); Sat, 23 May 2009 15:20:10 -0400 Received: from solo.fdn.fr ([80.67.169.19]:56985 "EHLO solo.fdn.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752077AbZEWTUJ (ORCPT ); Sat, 23 May 2009 15:20:09 -0400 Date: Sat, 23 May 2009 21:20:08 +0200 From: Samuel Thibault To: Jon Cc: KOSAKI Motohiro , linux-kernel@vger.kernel.org Subject: Re: dd if=/dev/random of=data.bin bs=512 count=1 Message-ID: <20090523192008.GD10166@const.famille.thibault.fr> Mail-Followup-To: Samuel Thibault , Jon , KOSAKI Motohiro , linux-kernel@vger.kernel.org References: <19ac3f7a0905170822q28255239nea01b56d52e3ddf8@mail.gmail.com> <2f11576a0905170901x41e15f65sf10bb5ee36050d14@mail.gmail.com> <4A184ABB.1070902@jguk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4A184ABB.1070902@jguk.org> User-Agent: Mutt/1.5.12-2006-07-14 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jon, le Sat 23 May 2009 20:12:59 +0100, a écrit : > KOSAKI Motohiro wrote: > >>Issuing this command, I expected to get a file 4096 bytes in size. > >>Could someone let me know if I have missed something..? Or is there a > >>problem with using /dev/random this way? > >> > >>if I have a count=10 it hangs forever (several hours). > >> > >>Changing to use /dev/urandom and it generates the file ok. > > > >you already have the answer. /dev/random might blocked, /dev/urandom > >doesn't. > > Is this a "feature" of /dev/random ? It is, as opposed to urandom > ..it does not seem very useful to have it able to block for so long. The feature is about to wait for random data to be available, not only pseudo-random data. Samuel