>>>不使用子菜单

# sudo vim /etc/default/grub
添加配置：GRUB_DISABLE_SUBMENU=y
From:http://tieba.baidu.com/p/2832768379

>>>引导某个分区

/etc/grub.d/文件夹下编辑 40_custom 文件。 也可以#mv 40_custom 01_custom把文件里的菜单放前一点。

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry 'Boot msdos2' {
        set root='hd0,msdos2'
        chainloader +1
}

menuentry 'Boot msdos3' {
        set root='hd0,msdos3'
        chainloader +1
}

menuentry 'Boot msdos7' {
        set root='hd0,msdos7'
        chainloader +1
}