Le 2012-02-28 08:01, Invisible a écrit :
> On 28/02/2012 10:02 AM, Patrick Elliott wrote:
>
>> Or, just a search on, "make usb flash drive bootable". Pages and pages
>> of ways to do it, most of them Linux based, but some others.
>
> Someone probably has a ready-made script to boot Linux from a flash
> drive, probably using Grub. But I'm trying to boot MS-DOS. I imagine
> that's going to be harder. (USB didn't /exist/ when MS-DOS was written,
> after all...)

This should be extremely simple.  MS-DOS talks to the BIOS, not the 
hardware directly.  If your BIOS can boot from USB, it'll provide the 
necessary functionality to run MS-DOS from a USB device.

The problem is that MS-DOS only understands FAT8 and FAT16, so you'll 
have to format your USB drive using those - which means using a thumb 
drive of 2GB or less.

- Format your USB drive to make sure it is completely empty.
- Copy IO.SYS from a bootable MS-DOS diskette to the USB drive.  FIRST. 
  As it has to be on sector 1.
- Copy MSDOS.SYS from the diskette to the USB drive.
- Copy COMMAND.COM from the diskette to the USB drive.
- ATTRIB +H +S *.SYS
- Voilà!
- You may now copy the rest of the DOS utilities to your USB drive.

Alternate way of doing it.
- Muck with your BIOS to make the USB drive look like C:
- Boot form the diskette
- FORMAT C: /S
- Tada!
- You may now copy the rest of the DOS utilities to your USB drive.

Note:
IO.SYS, MSDOS.SYS, COMMAND.COM, FORMAT.EXE and ATTRIB.EXE should to be 
of the same vintage for best results.

DISCLAIMER: I haven't tried it, but it should work.

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