grub 手動開機

grub> ls
(hd0) (hd0,msdos4) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1)
grub> ls (hd0,msdos1)/

grub> set root=(hd0,msdos1)
grub> linux /vmlinuz ro root=/dev/sda1
grub> initrd /initrd.img
grub> boot

Reference : 

Instigating a Manual Boot from the GRUB Prompt |