From owner-freebsd-current  Fri Nov 19 23:27:29 1999
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Date: Sat, 20 Nov 1999 02:26:41 -0500
From: Donn Miller <dmmiller@cvzoom.net>
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To: Alfred Perlstein <bright@wintelcom.net>
Cc: current@FreeBSD.ORG
Subject: Re: dd and gzip'd files
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Alfred Perlstein wrote:
> 
> On Sat, 20 Nov 1999, Donn Miller wrote:
> 
> > I recently tried using dd to transfer a binary image to floppy.
> > It was the Linux root disk image, color.gz.  Basically, dd works
> > ok with non-gzipped files, but with files in gzip format, it
> > chokes:
> >
> > root@lc186 floppies# dd if=color.gz of=/dev/rfd0
> > dd: /dev/rfd0: Invalid argument
> > 2453+1 records in
> > 2453+0 records out
> > 1255936 bytes transferred in 42.665771 secs (29437 bytes/sec)
> >
> > Notice the line that says:
> >
> > 2453+1 records in
> > ^^^^^^
> >
> > For some reason, it is offsetting to 1 before writing to disk.
> > Rawrite.exe does this correctly.  I tried with net.i, and it gave
> > me no problems:
> >
> > root@lc186 floppies# dd if=net.i of=/dev/rfd0
> > 2156+0 records in
> > 2156+0 records out
> > 1103872 bytes transferred in 39.172698 secs (28180 bytes/sec)
> >
> > I tried skip=0, but that didn't work.  Apparently, dd has some
> > limitations with what kinds of files you can transfer to
> > floppies.  I downloaded the files in binary format, so there's no
> > problems there.
> 
> no, you must write in block sized chunks when writing to raw
> devices or it'll get mad at you,  try figuring a way
> to use a blocksize of 16k and padding it to a 16k boundry.
> 
> if that doesn't work, then please tell us what you tried.

Thanks.  Here is what I tried:

root@lc186 floppies# dd obs=16k conv=osync if=color.gz
of=/dev/rfd0
2453+1 records in
77+0 records out
1261568 bytes transferred in 50.994527 secs (24739 bytes/sec)

It appears to have worked.  I guess the output block size of 16k
is key for floppies, then.  The conv=osync does the padding.

-- 
- Donn


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