Please, Master Budian: How to clear the GRUB in the U盘 MBR? - China DOS Union Forum

As the title says: Originally, the U disk GRUB was made to use bootlace.com --floppy --chs 0x00 to write GRUB into the MBR of the U disk. Now I want to use the U disk to boot into DOS, how to clear the GRUB in the U disk MBR?

Install the DOS boot code to the USB drive using the sys command, which will overwrite the GRUB boot code.

First, you boot the USB drive to GRUB, then execute in GRUB:

chainloader (fd0)/io.sys
boot

Then you enter DOS. In DOS, execute sys A: where A: is your USB drive.

Of course, you need to ensure that the DOS system files io.sys, msdos.sys, command.com, and the sys command itself are already on the USB drive.

Since the USB drive is recognized as a floppy disk by your BIOS, your USB drive has no MBR (even if there is an MBR, it is not visible under DOS), and there is only a FAT boot sector. The DOS boot sector you install using the sys command is on the first sector of the FAT. The GRUB boot sector is also on the first sector of the FAT.

Originally posted by ysyzygz at 2008-5-23 12:42 PM:
As the title: Originally, I used bootlace.com --floppy --chs 0x00 to write GRUB into the MBR of the USB flash drive to make the USB flash drive GRUB bootable. Now I want to boot into DOS from the USB flash drive, how to clear GRUB in the MBR of the USB flash drive?

Thanks to Master Budian.

Floor1　ysyzygz	Posted 2008-05-23 12:42
新手上路　Posts 3　Credits 8
As the title says: Originally, the U disk GRUB was made to use bootlace.com --floppy --chs 0x00 to write GRUB into the MBR of the U disk. Now I want to use the U disk to boot into DOS, how to clear the GRUB in the U disk MBR?

Floor2　不点	Posted 2008-05-23 13:30
银牌会员　Posts 1,115　Credits 2,491
Install the DOS boot code to the USB drive using the sys command, which will overwrite the GRUB boot code. First, you boot the USB drive to GRUB, then execute in GRUB: chainloader (fd0)/io.sys boot Then you enter DOS. In DOS, execute sys A: where A: is your USB drive. Of course, you need to ensure that the DOS system files io.sys, msdos.sys, command.com, and the sys command itself are already on the USB drive. Since the USB drive is recognized as a floppy disk by your BIOS, your USB drive has no MBR (even if there is an MBR, it is not visible under DOS), and there is only a FAT boot sector. The DOS boot sector you install using the sys command is on the first sector of the FAT. The GRUB boot sector is also on the first sector of the FAT.

Floor3　ysyzygz	Posted 2008-05-23 15:26
新手上路　Posts 3　Credits 8
Originally posted by ysyzygz at 2008-5-23 12:42 PM: As the title: Originally, I used bootlace.com --floppy --chs 0x00 to write GRUB into the MBR of the USB flash drive to make the USB flash drive GRUB bootable. Now I want to boot into DOS from the USB flash drive, how to clear GRUB in the MBR of the USB flash drive? Thanks to Master Budian.