I have a crashed laptop and used the following method to make a bootable usb drive (32 GB).
hdiutil convert -format UDRW -o ~/path/to/target.img ~/path/to/ubuntu.iso diskutil unmountDisk /dev/diskN sudo dd if=/path/to/downloaded.img of=/dev/rdiskN bs=1m
It did work and made a read only usb that acted as if it were a CD. I would like to now undo that (in OSx) but disk utility doesn't seem to be able to. When I click "Erase" it simply fails with
"Erase process has failed"
And details reveal
Name invalid. Operation failed...
Is there a way I can force format this USB drive (to either FAT 32 or OSX Extended) in OSx El Capitan?