bt wrote:
It doesn't make sense that if the "of=" device doesn't exist, then another pre-existing device, not mentioned in the command line, is overwritten.
It doesn't make sense to me, either. But I doubt whether this is a 'dd' bug. It doesn't know anything about devices: it just opens /dev/sda3 for reading and /dev/sdb3 for writing, and it doesn't do anything smarter than that. So if this trashes some other partition then it's most likely some problem with your partitioning.
