Anyone come across a bootable drive reformatting itself on a start up?

I've tried two different usb drives, erased partitioned, formatted as Msdos-fat, guid, converted an iso of Linux to dmg, renamed the partition and drive and burnt the dmg to disk with DD in terminal. Unmounted and ejected.

Remounted and looked at Disk Utility to double check the drive was still as I expected.

Then start up with alt key and the drive isn't recognised. Check in disk utility and it is no longer msdos fat, and the disk name has changed to the dmg file name. Wt......!!!

How was your day. More predictable, I hope.

#linux #mac #asknostr