dd if=/dev/zero of=test2.img bs=164K count=100000 oflag=dsync
dd bs=1M count=1024 if=/dev/zero of=test conv=fdatasyn
https://romanrm.net/dd-benchmark
dd bs=1M count=1024 if=/dev/zero of=test conv=fdatasyn
https://romanrm.net/dd-benchmark
https://www.howtogeek.com/427982/how-to-encrypt-and-decrypt-files-with-gpg-on-linux/