UbuntuHelp:GrubHowto/BootFloppy
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Making a GRUB boot floppy.
GRUB (GRand Unified Bootloader) is the boot manager installed by default in recent versions of Ubuntu Linux. It is an effort by the GNU project to provide a bootloader that supports the greatest number of operating systems. This document explains how to make a boot floppy that can either boot an installed operating system or present you with a GRUB command shell so that you can enter commands directly. It assumes that you are making the diskette on an Ubuntu Linux box.
1. Obtain root privileges.
sudo -s
2. Format the floppy with the ext2 filesystem:
mke2fs /dev/fd0
3. Mount the floppy and copy the files that GRUB needs to make it bootable:
mount /dev/fd0 /media/floppy mkdir /media/floppy/boot mkdir /media/floppy/boot/grub cd /boot/grub cp stage1 stage2 /media/floppy/boot/grub
If you want to boot the operating system already installed on the machine you are making the floppy from, also copy /boot/grub/menu.lst and /boot/grub/device.map to the corresponding directories on the floppy.
4. Unmount the floppy (umount /dev/fd0), then start GRUB in interactive mode by typing grub. You will see the GRUB command prompt (grub >). Enter these commands:
device (fd0) /dev/fd0 root (fd0) setup (fd0) quit
5. At this point, you have a bootable floppy. If you added the extra files mentioned above, you should get a standard GRUB screen when you boot from it, just as if you had booted from the hard drive.
6. If you want to be extra cautious, you can save a copy of the current machine's master boot record to a file on the floppy. The following example assumes the master boot record is on device hda; the file containing the boot record is named boot.mbr.
dd if=/dev/hda of=/media/floppy/boot.mbr bs=512 count=1
To restore it, you would just reverse the parameters of the dd command:
dd if=/media/floppy/boot.mbr of=/dev/hda bs=512 count=1
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