Copying memstick image to a USB (flash/thumb) drive

Ronald F. Guilmette rfg at
Wed Mar 27 21:19:44 UTC 2013

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


   Why exactly is "conv=sync" is there?

   Also, in practice what does it actually do?  (I've used dd plenty in my
   lifetime, but never found any reason to use conv= at all.  I always
   thought that it was... mostly... just an archaic leftover from the days
   when some big iron used EBCDIC that needed to get converted to ASCII
   or vise versa.)

   The dd man page describes the "sync" type of "conversion" thusly:
   "Pad every input block to the input buffer size.  Spaces are used for
   pad bytes if a block oriented conversion value is specified, otherwise
   NUL bytes are used."  Ummm... ok.  WTF is a "block oriented conversion
   value"?  How would I know if I had specified one?


    Why exactly is the "bs=10240" is there?  Wouldn't the default of 512
    do just as well?


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