Securely Wipe Disk

# fdisk -l /dev/sdX

# hdparm -i /dev/sdXN

To get disk size in the physical sectors you will need the known disk size in bytes divided with size of a single physical sector: 

# echo $((2000398934016 / 4096))

You can get size of the storage device or partition on it even with the: 

# blockdev --getsize64 /dev/sdXN

# dd if=data_source of=/dev/sdXN bs=${BytesInSector} count=${LogicalSectors}

https://wiki.archlinux.org/index.php/Securely_wipe_disk