Date: Wed, 27 Mar 2013 16:39:08 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: "Ronald F. Guilmette" <rfg@tristatelogic.com> Cc: freebsd-questions@freebsd.org Subject: Re: Copying memstick image to a USB (flash/thumb) drive Message-ID: <20130327213908.GA5447@dan.emsphone.com> In-Reply-To: <6148.1364418621@server1.tristatelogic.com> References: <6148.1364418621@server1.tristatelogic.com>
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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
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