Just an Update : umount -lfd was not enough
So I'm trying to embed a startup script in a Live custom ISO :
losetup -d /dev/loop0 umount -lfd /isodevice
And it works
Just an Update : umount -lfd was not enough
So I'm trying to embed a startup script in a Live custom ISO :
losetup -d /dev/loop0
umount -lfd /isodevice
And it works