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Chapter 1, Booting Linux
#2 Kill and Resurrect the Master Boot Record
HACK
Save the MBR
First, before you attempt anything potentially destructive, back up the current
MBR. Boot into Knoppix, and type the following command into a terminal:
knoppix@ttyp0[knoppix]$ sudo dd if=/dev/hda of=/home/knoppix/mbr_backup
bs=512 count=1
Change /dev/hda to match the drive you wish to back up. In your home direc-
tory, you should now see a 512-byte file called mbr_backup. Dd is used to cre-
ate images of entire hard drives, and in this case, a similar command is used;
however, it contains two new options:
bs and count. The bs (byte size) option
tells dd to input and output 512 bytes at a time, and the count option tells dd
to do this only once. The result of the command is that the first 512 bytes of
the drive (the MBR) are copied into the file. If for some reason you only want
to back up the boot sector (although it’s wise to always back up the partition
table as well), replace 512 with 446. Now that you have backed up the MBR,
copy it to a safe location, such as another computer or a CD-ROM.
The full 512-byte copy of the MBR contains the partition
table, so it gets out of sync whenever you change partitions
on your drive. If you back up the full MBR, be sure to update
your backup whenever you make partition changes.
Kill the MBR
Now you should know how to totally destroy the MBR. To do this, simply
use the same ...