Bootable Fat32 USB

Bobalandi · Post by **Bobalandi** » Mon Apr 28, 2008 8:47 pm

How would one go about booting their operating system from a usb drive.? If it was a fat16 usb drive, I might have better ideas, but as far as fat32 usb drives, how is it done.? I have found little information on this. Thanks in advance.

01000101 · Post by **01000101** » Mon Apr 28, 2008 9:01 pm

http://www.bootdisk.com/pendrive.htm

the HP utilities are wonderful for getting a USB flash drive formatted correctly, then you can use winwrite or whatever to put your OS on the drive. I'm not entirely sure if it is fat16 or 32.

Dex · Post by **Dex** » Mon Apr 28, 2008 9:01 pm

There has been many differant methods tyred, some more successful than others.
It seem more to do with what BIOS you have, as to whether it works or not.
You will find some info and links here:
http://menuet.2.forumer.com/index.php?showtopic=1112

Steve the Pirate · Post by **Steve the Pirate** » Tue Apr 29, 2008 8:11 am

I've done this - as far as I remember, it was as easy as running the Grub installer (this was on Linux), selecting root as the USB drive, and then typing Install or something.

I think this is the article I followed.

Bobalandi · Post by **Bobalandi** » Tue Apr 29, 2008 8:08 pm

Is it possible to use a fat12/fat16 bootloader, or must I create a fat32 one.?

Dex · Post by **Dex** » Wed Apr 30, 2008 9:54 am

Here how i understand it, first some BIOS use floppy emulation and some use hdd emulation, so its down to your BIOS.
Try putting a usb fob in the PC and booting, then enter the BIOS setup, look under boot priority (or something like that), see if it see the usb as a fdd or hdd etc.
It depends what you see in there as to what you can use.

Next as for fat16, its down to the size of the USB fob, theres a limit. if it's less than 2GB it will useally be formatted FAT (this is most likely fat16), if it says FAT32 its will be fat32.

A good and easy way to use USB to boot is to use Dos as a bootloader, to do this you first format it under win and click add sys files, then by adding you second stage bootload to the autoexe.bat it will boot your OS (if its a com file or mz exe).

TomT · Post by **TomT** » Wed Apr 30, 2008 1:17 pm

If you have your own bootloader that can boot an image file from a floppy, then add this code to boot from usb pen drive or floppy or cd:

;int 13h/8
;get sectors/track and qtyheads
;for possible booting from alternative medium like pen drive
;can boot from pen drive on Dell laptop at work
mov ah,8
mov dl,[0x505] ;drive#
int 13h ;GetCurrentDriveParameters
;test for error ??
and cx,111111b ;low 6 bits of cl contains sectors/track
mov [sectors_per_track],cx
movzx ax,dh ;this is highest head num not qty
inc ax
mov [qtyheads],ax

I tested this on only 1 machine. And as Dex says your Bios must support the floppy emulation.

TomT