Ok, I tried it this way. I made text file without any extension and put it to StartupItems directory in system with
diskutil unmount /dev/disk1
and also tried
diskutil eject /dev/disk1
Neither first nor second version doesn't work. I have still annoying requester with initialize/eject/ignore option on start of system.
i tried it myself. The dev/ part is wrong.
if you just write
It should work. Strange that you don't get an error.
Here i get one, and the hint to try
diskutil unmountDisk disk1