It means only the first x bytes (up to the interruption) have been zeroed out. If you run the same dd
command again and don't tell it to skip the first x bytes with skip=
, it will simply restart writing zeroes from the start of the disk. You'll loose some time, but that's it.
I don't know what you are trying to achieve, but for general reference I would like to point out that there might be better and more efficient tools:
SSDs should be erased using Secure Erase. It only takes a few seconds and doesn't wear out the drive.
If you want to format the drive or make it part of some RAID/ZFS/BTRFS/whatever array, and your commands are complaining about existing file systems, and you just want to remove all traces of them, wipefs
usually does the job in a few seconds.