I will be using a Raspberry Pi as an air-gapped computer to make secure encrypted transactions on the Ethereum BlockChain.
Once in awhile I will want to update the software I am using which will mean taking the SD card out of the Pi and inserting it into a laptop computer which is connected to the Internet. I would like to use some program or command line utility on the Pi to securely erase everything on the SD card before removing it as this will eliminate all possibility of sensitive information being read off the SD card by bad actors which may have compromised my laptop.
The following command typed in at the pi terminal conveys the idea of what I hope to accomplish:
shred --verbose *.*