Backing up the MBR

Just another note about restoring the boot loader for dual boot systems,
after Windows messes it up. In Linux, the “dd” command can read and
write to/from raw disks and files. If you have a floppy drive, creating
a boot disk is as simple as putting a floppy in the drive and typing

$ su
<type password>
# dd if=/dev/hda of=/dev/fd0 bs=512 count=1

This makes an exact copy of the MBR of the first hard drive, copying it
to a floppy disk. You can boot directly from this floppy, and see your
old boot menu. You can restore it by switching the “if=” and “of=”
(input file, output file) parameters.

If you don’t have a floppy drive, you can back it up to a file with

# dd if=/dev/hda of=/home/john/boot.mbr bs=512 count=1

Then you can boot into a CD-ROM distribution such as Knoppix, or often
use your Linux distribution’s installation CD to boot into rescue mode,
and restore it with:

$ su
# dd if=/mnt/hda5/john/boot.mbr of=/dev/hda bs=512 count=1

(you’ll need to find and mount the partition containing the directory
where you backed up the MBR for the “if” parameter–this is an example).


John Locke