How zero fill a hard disk?

Answer 1

There are various tools for Windows. However, if you have a Unix-derived system, chances are you will encounter the ddutility. The syntax for wiping a disk with dd is:

dd if=/dev/zero of=bs=

NOTE: If you proceed with this method, you must be VERY careful with the device path of the hard disk! if you choose the wrong one, it will mess up your data! (don't say you weren't warned)

Also, the bs option is optional (as it defaults to 512 bytes). 512 bytes is more accurate but slower (512 bytes is the size of a sector in a mechanical hard drive), but if you wish, you can set the block size to slightly increase the speed (the performance increase isn't necessarily linear - as in certain cases if the block size you set is too big, it might actually slow down instead).