Yesterday I installed Debian 10 on a second hard disk of my desktop PC (with Win10 already installed), when I rebooted the PC I was not able to start Win10.


*** BEFORE STARTING *** make sure you have a backup copy of your data since operations on grub could damage your data.

I solved this problem in a few steps you can find below:

  • First I had to retrieve the UUID of the disk
  • Then I had to modify  the file /etc/grub.d/40_custom by adding the following few lines at the end of the file.

Where 00000000-1111-2222-3333-444444444444 is the UUID I retrieved at first step, so you have to put there the UUID you retrieved from your hard disk.

  • The last step is the update of grub.

At the reboot I saw the Windows 10 entry in the GRUB OS list.