@p44 sorry, I think I gave you the wrong script! That is meant only for zeroing out rest of the disk (like we do in 1-click images). To erase the entire disk, you probably have to do something else. My understanding is that atleast for VMs in public cloud, this is done automatically. This came up as a security issue in SSD servers a long time ago. VPS providers were not formatting them because it reduces life span of the disk.
I guess as a hack, you can install plain ubuntu on the bare metal. And then, run the script command I posted earlier. Which probably has the same net effect as erasing. You have to run that command in the terminal/via ssh.