Daniel’s Blog.

Creating a DOS USB bootdisk under linux

Every now and then I need a DOS bootdisk to flash a BIOS or similar, and I only have linux with which to create it. I can never remember the quickest way to do this, so I’m documenting it here:

Lifted entirely from this webpage. I’m only archiving it here because content disappears over time.

I needed to upgrade the bios of my Computer (Intel).

But how to do it without windows?

In my case, Intel has many options for bios upgrading and one is the plain old DOS method. This is the best and fastest way to upgrade your bios with linux.
Create a FreeDOS based bootable usb-stick

* Download a FreeDOS image, i’ll use Balder for now.
* Prepare the usb-stick
o check partition (e.g cfdisk /dev/sda)
o mkfs.msdos /dev/sda1

Commands

qemu -boot a -fda balder10.img -hda /dev/sda
A:\> sys c:
A:\> xcopy /E /N a: c:

Check with

qemu -hda /dev/sda

There are, of course, many ways to do this. With recent VirtualBox versions supporting USB passthrough, I could do it entirely from a windows VM. Several other websites suggest installing grub onto the USB disk and having it boot a floppy disk image directly, which also seems like it would work. Your FAT-formatted USB drive would appear as C:, and you can just copy whatever content you like straight onto that.