The following worked:
# dd if=/dev/sdb of=cubietruck.img bs=512 count=6268927
6268927+0 records in 6268927+0 records out 3209690624 bytes (3.2 GB, 3.0 GiB) copied, 114.435 s, 28.0 MB/s
So bs= IS the drive blocksize.
This is the result of trying a number of different values for bs and count.
thank you
On 03/02/2017 10:02 PM, Fred Smith wrote:
On Thu, Mar 02, 2017 at 09:06:52PM -0500, fred roller wrote:
On Thu, Mar 2, 2017 at 8:36 PM, Robert Moskowitz rgm@htt-consult.com wrote:
dd if=/dev/sdb of=os.img bs=1M count=3210
I would recommend bs=512 to keep the block sizes the same though not a huge diff just seems to be happier for some reason and add status=progress if you would like to monitor how it is doing. Seems the command you have should work otherwise.
The dd blocksize has nothing to do with the disk sector size.
the disk sector size is the number of bytes in a minimal read/write operation (because the physical drive can't manipulate anything smaller).
the dd blocksize is merely the number of bytes read/written in a single read/write operation. (or not bytes, but K, or Kb, or other depending on the options you use.)
It makes sense for the bs option in dd to be a multiple of the actual disk block/sector size, but isn't even required. if you did dd with a block size of, e.g., 27, it would still work, it'd just be stupidly slow.
Fred