From owner-freebsd-questions@FreeBSD.ORG Wed Mar 27 21:46:21 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 090D02ED for ; Wed, 27 Mar 2013 21:46:21 +0000 (UTC) (envelope-from dan@dan.emsphone.com) Received: from email2.allantgroup.com (email2.emsphone.com [199.67.51.116]) by mx1.freebsd.org (Postfix) with ESMTP id ADDA935A for ; Wed, 27 Mar 2013 21:46:20 +0000 (UTC) Received: from dan.emsphone.com (dan.emsphone.com [172.17.17.101]) by email2.allantgroup.com (8.14.5/8.14.5) with ESMTP id r2RLd8XC093364 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 27 Mar 2013 16:39:09 -0500 (CDT) (envelope-from dan@dan.emsphone.com) Received: from dan.emsphone.com (smmsp@localhost [127.0.0.1]) by dan.emsphone.com (8.14.6/8.14.6) with ESMTP id r2RLd8ph096208 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 27 Mar 2013 16:39:08 -0500 (CDT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.14.6/8.14.6/Submit) id r2RLd89H096207; Wed, 27 Mar 2013 16:39:08 -0500 (CDT) (envelope-from dan) Date: Wed, 27 Mar 2013 16:39:08 -0500 From: Dan Nelson To: "Ronald F. Guilmette" Subject: Re: Copying memstick image to a USB (flash/thumb) drive Message-ID: <20130327213908.GA5447@dan.emsphone.com> References: <6148.1364418621@server1.tristatelogic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6148.1364418621@server1.tristatelogic.com> X-OS: FreeBSD 9.1-STABLE User-Agent: Mutt/1.5.21 (2010-09-15) X-Virus-Scanned: clamav-milter 0.97.7 at email2.allantgroup.com X-Virus-Status: Clean X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (email2.allantgroup.com [172.17.19.78]); Wed, 27 Mar 2013 16:39:09 -0500 (CDT) X-Spam-Status: No, score=-3.9 required=5.0 tests=ALL_TRUSTED,BAYES_00, RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on email2.allantgroup.com X-Scanned-By: MIMEDefang 2.73 Cc: freebsd-questions@freebsd.org 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 21:46:21 -0000 In the last episode (Mar 27), Ronald F. Guilmette said: > I've never used any FreeBSD memstick image before, but now I have reason > to do so. > > I'm reading the instructions for creating a bootable memstick that are > located on this page: > > http://www.freebsd.org/releases/9.1R/announce.html > > which include the following example of how to perform the copy: > > # dd if=FreeBSD-9.1-RELEASE-amd64-memstick.img of=/dev/da0 bs=10240 conv=sync > > Question: > > Why exactly is "conv=sync" is there? > > Question: > > Why exactly is the "bs=10240" is there? Wouldn't the default of 512 > do just as well? It looks like someone just copied a dd commandline from somewhere else, maybe something to do with tar files (since tar defaults to a 10k blocksize when writing to tape). conv=sync isn't needed since the source file is already a multiple of the target device blocksize (512 bytes), and bs=64k would be much faster when writing to cheap flash devices like USB sticks since they don't have a write cache and individual writes are slowish. -- Dan Nelson dnelson@allantgroup.com