Borrowed from Unixcraft…

#!/bin/bash
# Script Name: mbrback    http://igurublog.wordpress.com/downloads/script-mbrback/
# Requires: util-linux
# License: GNU GENERAL PUBLIC LICENSE Version 3 http://www.gnu.org/licenses/gpl-3.0.txt
# do not change these variables!
argsneeded=1
restoretype=””
back=””
devname=””
help ()
{
echo ‘mbrback version 1.0.0’
echo ‘Creates MBR and partition table backups of DEVICE named:’
echo ‘    HOST-DEVICE-MBR-back’
echo ‘    HOST-DEVICE-partition-back.sf’
echo ‘Restores MBR and partition table from specified backup file’
echo ‘Usage: sudo mbrback DEVICE [BACKUPFOLDER]’
echo ‘       (creates backup files of DEVICE)’
echo ‘Usage: sudo mbrback –restoreboot DEVICE [BACKUPFILE]’
echo ‘       (restores MBR boot code only)’
echo ‘Usage: sudo mbrback –restorefullmbr DEVICE [BACKUPFILE]’
echo ‘       (restores entire MBR)’
echo ‘Usage: sudo mbrback –restorepart DEVICE [BACKUPFILE.sf]’
echo ‘       (restores partition table)’
echo ‘Example: sudo mbrback sda’
echo ‘         (creates MBR and partition table backups of’
echo ‘          /dev/sda in current folder)’
echo ‘Example: sudo mbrback /dev/sda’
echo ‘         (creates MBR and partition table backups of’
echo ‘          /dev/sda in current folder)’
echo ‘Example: sudo mbrback sda /mybackups’
echo ‘         (creates MBR and partition table backups of’
echo ‘          /dev/sda in /mybackups)’
echo ‘Example: sudo mbrback –restoreboot sda /mybackups/sys-sda-MBR-back’
echo ‘         (restores MBR boot code of /dev/sda using’
echo ‘          /mybackups/sys-sda-MBR-back)’
echo ‘Example: sudo mbrback –restorepart sda /mybackups/sys-sda-partition-back.sf’
echo ‘         (restores partition table of /dev/sda using sfdisk file ‘
echo ‘          /mybackups/sys-sda-partition-back.sf)’
echo
echo “When restoring, mbrback will always tell you what it’s going to do”
echo “and allow you to abort before it writes to disk.”
echo
echo “Instructions and updates:”
echo “http://igurublog.wordpress.com/downloads/script-mbrback/”
echo
}
index=0
while [ “$1” != “” ];
do
if [ “${1:0:1}” = “-” ]; then
case “$1” in
–help | -help )
help
exit
;;
–restoreboot )
if [ “$restoretype” = “” ]; then
restoretype=”boot”
else
echo ‘mbrback: can only use one restore option’
exit 1
fi
;;
–restorefullmbr )
if [ “$restoretype” = “” ]; then
restoretype=”fullmbr”
else
echo ‘mbrback: can only use one restore option’
exit 1
fi
;;
–restorepart )
if [ “$restoretype” = “” ]; then
restoretype=”part”
else
echo ‘mbrback: can only use one restore option’
echo
help
exit 1
fi
;;
* )
echo “mbrback: Unknown option $1”
echo
help
exit 1
;;
esac
else
let “index+=1”
case $index in
1 )
devname=basename "$1"
if [ ! -b “/dev/$devname” ]; then
echo “mbrback: /dev/$devname is not a valid device”
exit 1
fi
;;
2 )
back=”$1″
;;
* )
echo “mbrback: Too many arguments”
exit 1
;;
esac
fi
shift
done
if (( index < $argsneeded )) || [ “$devname” = “” ]; then
echo “mbrback: missing arguments”
echo
help
exit 1
fi
if [ whoami != “root” ]; then
echo ‘mbrback: must be run with sudo’
exit 1
fi
sysname=$HOSTNAME
if [ “$restoretype” = “” ]; then
# create MBR and table backups
if [ “$back” = “” ]; then
back=pwd
else
if [ ! -d “$back” ]; then
echo “mbrback: $back is not a valid backup folder”
exit 1
fi
fi
dd if=/dev/$devname of=”$back/$sysname-$devname-MBR-back” bs=512 count=1
sfdisk -d /dev/$devname > “$back/$sysname-$devname-partition-back.sf”
else
# restore
if [ “$back” = “” ]; then
echo “mbrback: you must specify a backup file”
exit 1
elif [ ! -f “$back” ]; then
echo “mbrback: file not found – $back”
exit 1
fi
if [ “$restoretype” = “boot” ] || [ “$restoretype” = “fullmbr” ]; then
sfhead=head --bytes=21 "$back"
if [ “$sfhead” = “# partition table of ” ]; then
echo “mbrback: $back is not an MBR backup file”
exit 1
fi
if [ “$(stat -c%s “$back”)” != “512” ]; then
echo “mbrback: $back is wrong size for an MBR backup file”
exit 1
fi
fi
if [ “$restoretype” = “part” ]; then
sfhead=head --bytes=21 "$back"
if [ “$sfhead” != “# partition table of ” ]; then
echo “mbrback: $back not a valid sfdisk backup file”
exit 1
fi
echo
echo “You are about to overwrite your /dev/$devname partition table with”
echo “the contents of $back”
echo
echo “WARNING!!! Unless the partition table has been damaged or you”
echo “           have accidentally deleted a partition, you should abort.”
echo
echo “WARNING!!! Restoring the partition table from an out-of-date backup”
echo “           may render ALL the data on your drive unreadable.”
echo
echo “WARNING!!! Do not proceed if /dev/$devname is mounted.”
echo
elif [ “$restoretype” = “boot” ]; then
echo
echo “You are about to overwrite your /dev/$devname MBR boot code with”
echo “the contents of $back”
echo
echo “WARNING: Restoring your MBR boot code from an out-of-date MBR backup”
echo “         file may render your computer unbootable.”
elif [ “$restoretype” = “fullmbr” ]; then
echo
echo “You are about to overwrite your ENTIRE /dev/$devname MBR with”
echo “the contents of $back”
echo
echo “WARNING!!! The full MBR contains both boot code and the drive’s”
echo “           partition table.  Unless the partition table has been”
echo “           damaged or you have accidentally deleted a partition”
echo “           you should abort and restore boot code only with”
echo “           –restoreboot instead.”
echo
echo “WARNING!!! Restoring your full MBR from an out-of-date MBR backup may”
echo “           render your computer unbootable and ALL the data on your”
echo “           drive unreadable.”
echo
echo “WARNING!!! Do not proceed if /dev/$devname is mounted.”
fi
echo
echo “Do you want to proceed? (you must type yes to proceed)”
read s1
if [ “$s1” != “yes” ]; then
echo “mbrback: no changes made – aborted at user request”
exit 2
fi
if [ “$restoretype” = “part” ]; then
sfdisk /dev/$devname < “$back”
elif [ “$restoretype” = “boot” ]; then
dd if=”$back” of=/dev/$devname bs=448 count=1
elif [ “$restoretype” = “fullmbr” ]; then
dd if=”$back” of=/dev/$devname bs=512 count=1
fi
echo “/dev/$devname was updated”
fi
exit 0