如何非破坏性地检查grub2是否安装在引导扇区中或者是否被grub1链式加载,而无需重启?

Modified on: Thu, 06 Jun 2019 14:00:02 +0800

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进行升级。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而没有重新引导,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?

最佳答案

我偶然发现了grub2 debian源代码包中的答案。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


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