Shredding

Shredding is overwriting data in a file or storage with random bits, making it nearly impossible to recover.

Shred a single file

# shred
sudo shred -vfz path_name

# Shred after finding files
## cd into the directory you want to recursively shred 48 times
find . -type f -print0 | xargs -0 shred -fuzv -n 48

Shred a disk

blkdiscard (Recommended)

# basic
blkdiscard /dev/disk_name

# secure
blkdiscard --secure /dev/disk_name

Because blkdiscard is a host command, it doesn't communicate to the SSD controller directly.

SSDs typically include more flash memory than they advertise to the host OS (spare space to account for bad sectors by design).

The controller knows where all the bits are located, but not the host so there may be 99% guarantee that the data was erased, but not 100%.