From owner-freebsd-questions@FreeBSD.ORG Wed Mar 27 21:57:44 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 127975AC for ; Wed, 27 Mar 2013 21:57:44 +0000 (UTC) (envelope-from danny@clari.net.au) Received: from pigeon.clari.net.au (pigeon.clari.net.au [203.29.224.25]) by mx1.freebsd.org (Postfix) with ESMTP id CE1B95E8 for ; Wed, 27 Mar 2013 21:57:43 +0000 (UTC) Received: from [192.168.100.102] (c114-76-1-137.eburwd4.vic.optusnet.com.au [114.76.1.137]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: danny@clari.net.au) by pigeon.clari.net.au (Postfix) with ESMTPSA id B745DAC61C3 for ; Thu, 28 Mar 2013 08:52:26 +1100 (EST) Message-ID: <51536A01.6000005@clari.net.au> Date: Thu, 28 Mar 2013 08:52:01 +1100 From: Daniel O'Callaghan User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 To: freebsd-questions@freebsd.org Subject: Re: Copying memstick image to a USB (flash/thumb) drive References: <6148.1364418621@server1.tristatelogic.com> In-Reply-To: <6148.1364418621@server1.tristatelogic.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 27 Mar 2013 21:57:44 -0000 On 28/03/2013 8:10 AM, Ronald F. Guilmette wrote: > Question: > > Why exactly is "conv=sync" is there? I found this on http://www.mkssoftware.com/docs/man1/dd.1.asp If you specified conv=sync and this input block is smaller than the specified input block size, dd pads it to the specified size with null bytes. When you also specify a block or unblock conversion, dd uses spaces instead of null bytes. So the last block of output gets padded with 0x00 at the end to fill the input block size (from bs=...) > Question: > > Why exactly is the "bs=10240" is there? Wouldn't the default of 512 > do just as well? It would, but then you would have FILESIZE/512 reads and writes instead of FILESIZE/10240 reads and writes - 20 times more. The end result is the same, but the large bs makes the operation go faster. I routinely use bs=655360 simply because it is a big number divisible by 512, which I can easily remember. 512000 would do just as well, though... Danny