Relatively safe method, if you already have a filesystem on the drive: 1. make sure 'discard' or equivalent mount option is enabled 2. write some data to a test file 3. hdparm --fibmap testfile 4. make sure data is actually there: sync hdparm --read-sector <a sector number from the above command> /dev/sda 5. rm testfile sync hdparm --read-sector <a sector number from the above command> /dev/sda sector should now be all 0's Unssafe method, if there is no data on the drive that you care about: write some data to the first sector hdparm --trim-sector-ranges 0:1 /dev/sda hdparm --read-sector 0