我们正在将几个系统从Debian Lenny升级到Squeeze,我想确保我没有错过任何grub2安装.默认情况下,从grub1挤压链启动加载,您必须运行upgrade-from-grub-legacy升级.所以我希望能够远程检查是否已经在磁盘引导扇区中安装了grub2而没有重新启动,并且没有覆盖引导扇区.
有没有什么比做硬盘驱动器的早期块的hexdump更容易并尝试识别特定于grub2的字节？
我在grub2 debian源代码包中偶然发现了答案.事实证明它确实需要转储bootsector – 因此单独打包的脚本可能很有用.这是一个脚本(只是官方函数的包装器),它将告诉您grub2是否已安装到引导扇区中.它可以很容易地修改为类似的用途.
#!/bin/bash
set -e
if [ "$UID" -ne "0" ]; then
echo Must be run as root
exit 99
fi
scan_grub2()
{
if ! dd if="$1" bs=512 count=1 2>/dev/null | grep -aq GRUB; then
# No version of GRUB is installed.
echo Grub could not be found
return 1
fi
# The GRUB boot sector always starts with a JMP instruction.
initial_jmp="$(dd if="$1" bs=2 count=1 2>/dev/null | od -Ax -tx1 | \
head -n1 | cut -d' ' -f2,3)"
[ "$initial_jmp" ] || return 1
initial_jmp_opcode="${initial_jmp%% *}"
[ "$initial_jmp_opcode" = eb ] || return 1
initial_jmp_operand="${initial_jmp#* }"
case $initial_jmp_operand in
47|4b|4c|63)
# I believe this covers all versions of GRUB 2 up to the package
# version where we gained a more explicit mechanism. GRUB Legacy
# always had 48 here.
return 0
;;
esac
return 1
}
if scan_grub2 "/dev/sda"; then
echo Found grub 2
else
echo Did not find grub 2
#Uncomment the next line to upgrade
#upgrade-from-grub-legacy
fi
