装两块硬盘，两个系统容易出问题​

sudo fdisk -l
cat /etc/default/grub

Add the output details.

Hi le，

Sorry I'm new here and I guess it could be the issue of boot. I'd like to translate your post into Chinese so that more people may understand your question.

Also, there was a post about how to deal with installation issues, written in Chiness though. Here, 不管是先装Win10还是先装Deepin，启动问题轻松搞定- Community - Deepin Technology

层主有两块硬盘，分别装了win10 和 deepin, 但他无法用 grub 检测到deepin的盘，（提示sda 的许可被拒绝，而 deepin 安装在 sdc 中）。层主已经用 os-prober 等方法，但还没能解决。

Regards,

Maybe because windows fast boot cause the drive can't be mounted.

Adding solution despite being late so people with same issue in the future can refer here.

Install os-prober with sudo apt install os-prober.

Run sudo fdisk -l and note the boot partition. Now run lsblk and make sure the partition is mounted. It should be /boot/efi or /boot. If it is not mounted, mount it under /boot/efii.

Now run sudo nano /etc/default/grub and add the following line at the end in a new line:

GRUB_DISABLE_OS_PROBER=false

Press Ctrl+O and Ctrl+X. Now run sudo update-grub. Now it should find your windows installation and add it to the entry. Nest time you boot, you should see an entry for Windows there.