해결방법사이트
https://songskim.wordpress.com/2015/08/22/%EC%9C%88%EB%8F%84%EA%B7%B810-%EC%97%85%EA%B7%B8%EB%A0%88%EC%9D%B4%EB%93%9C-%ED%9B%84-grub-%EC%82%B4%EB%A0%A4%EB%82%B4%EA%B8%B0/
