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#! /bin/bash
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# bash is important because for echo -e
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# edit the magic number of boot sector (the last two bytes)
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# (c) 2001, Thomas Lange, lange@informatik.uni-koeln.de
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seek=510
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usage() {
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cat <<EOF
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bootsector [-edlvh] device
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Read or write the magic number (the last two bytes) of a boot
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sector. Writing 0x0000 to it disables booting from this boot sector.
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The value 0xAA55 enables booting from this boot sector.
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-e enable the boot sector
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-d disable the boot sector
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-l list the magic number hexadecimal
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-v list the magic number in a verbose way
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-h print this help
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Examples:
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# bootsector -e /dev/hda
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# bootsector -l /dev/hda
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0000000 aa55
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# bootsector -d /dev/hda
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# bootsector -l /dev/hda
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0000000 0000
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# bootsector -v /dev/hda
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Boot sector /dev/hda disabled.
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bootsector is written by Thomas Lange, lange@informatik.uni-koeln.de, 2001.
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EOF
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exit 0
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}
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readbb() { # read last two bytes from boot block
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dd bs=1c skip=$seek count=2 if=$1 2>/dev/null|od -x|grep -v 0000002
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}
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writebb() { # write last two bytes of boot block
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dd bs=1c seek=$seek of=$1 2>/dev/null || echo "Can't write to boot block $1"
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}
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arch=`dpkg --print-installation-architecture`
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[ "$arch" = "i386" ] || {
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Currently, only i386 architecure is supported.
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exit 1
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}
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getopts e:d:l:v:h opt
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case $opt in
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h) usage ;;
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e) echo -ne "\x55\xaa" | writebb $OPTARG ;;
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d) echo -ne "\x0\x0" | writebb $OPTARG ;;
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l) readbb $OPTARG ;;
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v) bs=`readbb $OPTARG`
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case $bs in
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"0000000 0000") echo "Boot sector $OPTARG is disabled." ;;
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"0000000 aa55") echo "Boot sector $OPTARG is enabled." ;;
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*) echo "Unknown boot sector $bs" ;;
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esac
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;;
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*) usage; exit 1 ;;
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esac
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