While installing Ubuntu basic server on a flash drive within Virtual Box I get the error
/usr/sbin/grub-setup: error: hd0 appears to contain a iso9660 filesystem which isn't known to reserve space for DOS-Style boot. installing grub there could result in FILESYSTEM DESTRUCTION if valuable data is overwritten by grub-setup (--skip-fs-probe disables this check, use at your own risk).
however, when I use grub-install --skip-fs-probe /dev/sda it says "Unrecognized option --skip-fs-probe" if I use grub-install /dev/sda --skip-fs-probe it says "Unrecognized option --skip-fs-probe"
I decided to run VirtualBox using VBoxManage internalcommands createrawvmdk -filename C:\USB.vmdk -rawdisk \\.\PhysicalDrive1 and to mount the USB so that I can write directly to it, but this didn't work to avoid the error.
I will continue to try to find ways to get around this, in the meantime I thought you should know of the errors.