View Full Version : Dual Boot Grub - Windows 10 Not Showing -

January 16th, 2019, 07:13 PM
I installed Ubuntu last night to set up a dual boot process. I have SSD where my windows 10 install is and a 500 GB empty HDD where I decided to install ubuntu.
I split the HDD so that I have about 130gb of space for Ubuntu.

Below are the steps I followed:

Split HDD to 130gb of unallocated
set up swap 16gb
set up efi 200mb
set up root on remaining space
Selected my windows 10 SSD for grub

After reboot, Ubuntu os loaded directly without grub menu. Tried the ESC method to load grub and windows 10 was not shows.
Started looking online and tried a few steps.

adding custom windows 10 to 40_custom file

In further reading, I realized that both installs need to be in UEFI or BOOT, this is where I think I messed up.

Windows 10 is on BOOT ( i used the terminal in ubuntu to navigate to /Windwos/Panther/setupact.log and saw detected boo environment = BOOT)

I don't know how to resolve this now. The windows 10 install is quite important to me as it has a lot of files that I need that are not backed up.
The Ubuntu install I would not mind reinstalling as it was a fresh install anyway.

Can I please get some help in resolving this. Attaching the file generated by boor-repair. Thank you much!


January 16th, 2019, 07:33 PM
With systems in different boot modes, you cannot dual boot from grub boot menu.
Only because you have two drives, you can dual boot with Windows in BIOS boot mode and Ubuntu in UEFI mode, but only from UEFI boot menu, not grub.

Windows requires MBR partitioning with BIOS boot and requires gpt partitioning for UEFI boot.
You can (but not recommended) install Ubuntu in UEFI boot mode on MBR partitioned drive. This is what you did originally.
But you then reinstalled grub in BIOS boot mode to convert install from UEFI to BIOS, but used default fix in Boot-Repair which installs grub to MBR of all drives. You really want Windows boot loader in MBR of sda & grub in MBR of sdb. And then BIOS set to boot from sdb drive. Since grub only boots working Windows and Windows will turn fast start up back on, or need chkdsk, you can then directly boot Windows from BIOS and sda drive. Still best to have Windows repair flash drive or know if & how to use repair console in Windows installer.

Boot-Repair's advanced mode may let you choose your Windows install and choose to install a generic Windows type boot loader to MBR of sda. If fast start up on, it may not see your Windows install. Then you have to use your Windows repair/recovery drive to run fixMBR command in Windows command line.

Fast Start up off (always on hibernation), note that Windows turns this back on with updates

As soon as you get systems working, make good backups & develop a regular procedure to backup both Windows data & Ubuntu data & settings.

Since Ubuntu on second drive, I do prefer to use gpt partitioning. I used it for BIOS boot with my old XP system on separate MBR drive for years before my UEFI systems. You could convert sdb to gpt, but would need to add a bios_grub partition for grub to correctly install for BIOS boot.
Since you have a lot of data, probably easier to stay with BIOS boot, but when Windows totally breaks and you have to reinstall, you may want to consider conversion to UEFI/gpt for all drives.

January 16th, 2019, 07:49 PM
Thank you oldfred for a quick reply. To understand correctly. I need to do this "Windows boot loader in MBR of sda & grub in MBR of sdb. And then BIOS set to boot from sdb drive"
For the following solution: Boot-Repair's advanced mode may let you choose your Windows install and choose to install a generic Windows type boot loader to MBR of sda.
In Boot-repair, would I do the following option, and select sda windows? Sorry you gave me a lot of info that i couldn't digest fully I am very new to all the technical terminology.

, http://pix.toile-libre.org/upload/original/1335263417.png

IF the following does not work then attempt a windows recovery approach, with the following command in command line. bootrec /fixmbr?

Thank you so much for your help!

January 16th, 2019, 10:13 PM
Yes, if Windows fast start up is off, or Windows has no issue, Boot-Repair will see Windows as one of the choices in the combo box that shows 12.04 in example.
But if it cannot see Windows, not sure if it will let you force an install of syslinux which is the Windows type boot loader.
We can manually force a syslinux install directly from Ubuntu if required. But if Boot-Repair does not work, better to then use Windows tools to fix Windows.

January 17th, 2019, 12:28 AM
Thank you oldfred. I will try this approach in about 3 hrs when I get home. Could you give me directions on " force a syslinux install directly from Ubuntu", I want to have that ready as a tool In case I am unable to make a windows recovery USB.

Are these the two commands in the terminal?

sudo apt-get install syslinux

sudo dd if=/usr/lib/syslinux/mbr.bin of=/dev/sda

Do I leave the /dev/sda as above or change to /dev/sda1 or /dev/sda2

January 17th, 2019, 03:44 AM
SUCCESS!! - Windows 10 USB fixed the issue on sda, if I hit f12 and select the windows drive windows 10 loads correctly. I also set my boot to be sdb. Now in sbd, can I have grub recognize the windows 10 update in sda , so that I can select from grub which system to load on? Thank you so much for your help!

January 17th, 2019, 05:28 AM
This should add Windows to grub menu, if Windows is not hibernated nor needs chkdsk.

sudo update-grub

Then you can dual boot from Ubuntu drive as long as Windows works.
If it does not work then you can try to boot from UEFI/BIOS directly from Windows drive, perhaps with f8 to get into repair mode.
Or if bigger Windows issues, you need the Windows repair/recovery disk.

January 17th, 2019, 04:22 PM
Thank you! I have everything set up as I need.