从外部设备启动进入grub rescue模式的求助（含Boot-Repair启动信息报告）

我折腾了好半天，试了各种办法都没能解决从外部设备启动后进入grub rescue模式的问题。最后我用Ubuntu Live USB启动，获取到了Boot-Repair的启动信息报告，具体内容如下：

============================== Boot Info Summary ===============================

 => Windows is installed in the MBR of /dev/sda.
 => Grub2 (v2.00) is installed in the MBR of /dev/sdb and looks at sector 1 of 
    the same hard drive for core.img. core.img is at this location and looks 
    for (,msdos2)/boot/grub. It also embeds following components:
    
    modules
    ---------------------------------------------------------------------------
    fshelp fat part_msdos biosdisk
    ---------------------------------------------------------------------------

sda1: __________________________________________________________________________

    File system:       vfat...

备注：内容来源于stack exchange，提问作者user1551