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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:  <>
In-Reply-To: <>
References:  <>

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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:
> 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

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