我的windows重装了，然后没有了grub2启动项，我就用u盘刻了系统，然后按照百科里面的修复启动项结果没有成功，终端输入结果如下，我曾在终端下备份过grub，不知道能不能恢复？求教大家怎么修复
deepin@deepin:~$ su
密码：
root@deepin:/home/deepin# sudo mount /dev/sda1 /mnt
Mount is denied because the NTFS volume is already exclusively opened.
The volume may be already mounted, or another software may use it which
could be identified for example by the help of the 'fuser' command.
root@deepin:/home/deepin# sudo chroot /mnt
chroot: failed to run command ‘/bin/bash’: No such file or directory
root@deepin:/home/deepin# update-grub
/usr/sbin/grub-probe：错误： failed to get canonical path of /cow.
root@deepin:/home/deepin# grub-probe -t device /boot/grub
grub-probe：错误： failed to get canonical path of /cow.
root@deepin:/home/deepin# grub-install /dev/sda
grub-probe：错误： failed to get canonical path of /cow.
Path `/boot/grub' is not readable by GRUB on boot. Installation is impossible. Aborting.
root@deepin:/home/deepin# grub-install --recheck /dev/sda
grub-probe：错误： failed to get canonical path of /cow.
Path `/boot/grub' is not readable by GRUB on boot. Installation is impossible. Aborting.
root@deepin:/home/deepin#