Please don't direct me to the dd thread here in the forums, it has a ton of examples, but no clear explanation about my question. I already read it.
My question is this.
When running dd like so ->
dd if=/dev/zero of=/dev/sda
I know the hard drive get's wiped. However it takes a very, very long time.
If I do this instead
dd if=/dev/zero of=/dev/sda bs=4K
It speeds up considerably. What is the difference?
Furthermore, there are so many examples, I can't help that most are careless use to do this. Could someone please go into detail about the best most efficient and correct way to do this to a standard hard drive and also what would be the best way to wipe a solid state drive and at last a flash drive.
I understand this may be a beginner question, but I hope for a professional answer. Many times I used drive partitioning software on windows that have options for standard and secure wipes later to find out they are tiny linux programs in dos mode that might acutally be using standard linux utilities.
I would like to be able to fully understand how to operate critical system utilities such as dd - Please point me in the right direction if you can.
The last part of my question is more difficult.
How can I run dd to wipe the first megabyte and last megabyte of the hard drive without having to manually get information about my hard drive on sectors and so on.