http://wiki.ubuntu.com.cn/GRUB%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B#.E6.88.91.E5.BA.94.E8.AF.A5.E5.AD.A6.E4.B9.A0.E8.BF.99.E9.97.A8.E6.95.99.E7.A8.8B.E5.90.97.EF.BC.9F
