akonsu wrote:
hello,
i wanted to create an ISO image of a CDROM, so i ran this command:
dd if=/dev/cd0a of=my.iso
and i waited and waited for about 30 minutes until i just gave up and
pressed ^C. the resulting iso file was much larger than the source disc.
try
dd if=/dev/rcd0c of=disk.iso bs=32k
note the "rcd0c" instead of "cd0a". The 'a' vs. 'c' doesn't (seem to)
matter, I just philosophically prefer the 'c' implying entire disk,
rather than just one partition. The "raw" mode of access makes a lot of
difference here.
I put the "bs=32k" in there for a bit of additional performance, but it
turns out that without the "bs=" line, it didn't work at all. After a
little thought (and testing), I remembered that on most modern
platforms, CDROM drives have a 2k block size, so apparently dd has
trouble moving 512 bytes at a time out of CDROM drives. I confirmed
that "bs=2k" worked, "bs=1k" does not, so I might possibly be not
totally wrong on that. "bs=32k" seemed to go about twice as fast as
"bs=2k".
Well, I learned something. :)
Nick.
