To write floppies I use dd(1):

dd if=disk.image.filename of=/dev/fd0a bs=9216

I use a blocksize of 9216 to speed matters up (9216 = 18*512 or a single
track )

--et

>
> Hello!
> 
> I rarely use floppies, the newest PCs we bought didn't
> even have diskette drives!  I'm trying to write two
> NetBSD install floppies to set up a machine for my
> brother-in-law (Hi Mike! ;-) and it occurs to me that
> I don't know the device file to write to.  I've looked
> in the install docs and NetBSD guide, but if it is in
> there I'm missing it.
> 
> The install floppies will be 3.5" DSHD (80,2,18).  It
> would also be useful to know which file to use for
> 3.5" DSDD (80,2,9), so that I can play with pcemu.
> Any help would be most welcome.
> 
> Regards,
>   - Andy Ball.