Help with dual booting Win 10 and Ubuntu

flexmcmurphy · 11 Apr 2021

Hello,

My laptop has two hard drives: in the main location is an SSD with Win 10 and in the DVD drive bay is an HDD with Ubuntu. Both are Legacy BIOS. Win 10 uses MBR in /dev/sda1 and Ubuntu GRUB2 which is at /dev/sdb.

I am trying to use the Windows bootloader to give me a selection screen where I can choose Win 10 or Ubuntu and have a configurable timeout.

I think I am almost there. I installed EasyBCD and added Ubuntu to the bootloader. When I boot up I can choose between Win 10 and Ubuntu... if I choose Win 10 it continues booting into Win 10 but if I choose Ubuntu it actually reboots first then takes me to the GRUB2 menu for Ubuntu. If I then choose Ubuntu from the GRUB2 menu if carries on booting into Ubuntu. If I choose Win 10 from the GRUB2 menu it goes back to the Win 10 bootloader screen where I again need to choose Win 10 OR Ubuntu but if I choose Win 10 this time it carries on booting in to Windows whereas once again if I choose Ubuntu it has to reboot first then I am back to the GRUB2 menu.

Sorry this is so long! My question: is that normal behavior? If you select Ubuntu from the Win 10 bootloader screen it first has to reboot then the GRUB2 menu appears. Why does it have to reboot if I choose Ubuntu from the Win 10 bootloader screen? Did I set it up wrong with EasyBCD?

Cheers,

Flex

NavyLCDR · 11 Apr 2021

That's the normal process. It's called chain loading. You have to remove the option to boot into Windows from the grub menu so that grub boots directly into Linux with no delay.

flexmcmurphy · 11 Apr 2021

But I'm not sure if you understood me or I understand you...

I get that Windows bootloader has to send me to the GRUB2 loader on the HDD where Linux is but I'm wondering why does my laptop have to reboot?

When I select Ubuntu on the Windows bootloader screen I can hear it rebooting. Why doesn't it just go straight to the GRUB2 screen without a reboot?

Flex

NavyLCDR · 11 Apr 2021

Because the grub bootloader can only be loaded by the system BIOS when the computer boots.

flexmcmurphy · 11 Apr 2021

Thank you @NavyLCDR

Would it be the same if I swapped the disks around? So I put the HDD with Ubuntu in the main SATA drive bay and the SSD with Win 10 into the DVD caddy?

In that case I guess I could boot into Ubuntu from the GRUB2 menu without needing an "extra" reboot.... but... if I selected Windows from the GRUB2 menu would I need an extra reboot to make Win 10 load from the SSD now in the DVD caddy?

I'll give that a try now.

Flex

Megahertz · 11 Apr 2021

My suggestion is to set HDD (Ubuntu) as BIOS first boot option . Under grub you select Ubuntu or Windows.
Remove the Ubuntu option under Windows boot manager.

I use the boot menu (F12 on my MB) to choose Lubuntu and have disabled Windows on Grub boot manager.

bro67 · 11 Apr 2021

You can only use one bootloader period. Clover is the better, BURG is another.

topgundcp · 11 Apr 2021

My laptop has two hard drives: in the main location is an SSD with Win 10 and in the DVD drive bay is an HDD with Ubuntu. Both are Legacy BIOS. Win 10 uses MBR in /dev/sda1 and Ubuntu GRUB2 which is at /dev/sdb.

This is your whole problem. What you should have done is to put GRUB in sdb1 and Windows Manager in sda1 so that Windows Boot Manager is in control.
So what suggested above will not make any difference. GRUB is still in control of booting process.
To fix your problem. You will need to:

Move GRUB from sdb to sdb1
|grub2 - how to move grub boot from one partition to another in linux - Ask Ubuntu
Rebuild The Windows Boot Manager ie. create a brand new BCD to boot Windows 10.
Once done with steps 1 and 2 above. Windows will not know UBUNTU exists and vice versa.
Depend on the priority set in the BIOS, it will boot directly into that OS.
However, you can boot either one from Boot Menu (Using whatever key that your Laptop assigned to: F2, F10....)
Since I hate Dual Boot and seldom boot into Linux, I will stop here.
Now, go to step 4 to create dual boot.
Use Easy BCD to create an entry for dual boot with UBUNTU. Once done, you should get a nice GUI dual Boot Menu
and it will boot directly into either Windows or UBUNTU.

Here's the detailed explanation: How can I move windows 10 boot files to another drive to allow linux

Megahertz · 11 Apr 2021

Dino,
How do you know that the Windows boot manager and Grub are on wrong partitions?
I would say that Windows is on disk sda, partition 1 and Ubuntu is on disk sdb and each boot manager and boot loader is on the right place

flexmcmurphy · 12 Apr 2021

Following advice from @NavyLCDR "... the grub bootloader can only be loaded by the system BIOS when the computer boots."

I then swapped my disks around. I had to physically swap the locations because despite many hours of effort I am not able to get my Dell laptop to default boot from the drive in the DVD caddy. When I try to save that change in the BIOS the screen just freezes and the change isn't saved.... anyway that's a different issue!

So now I boot first in to the HDD containing Linux and its GRUB2 boot loader/boot manager menu screen. Now when I choose to boot Ubuntu OR Windows from the GRUB2 menu I am not hearing a reboot happen.

Now I don't understand why I CAN go straight from the GRUB2 menu to loading Windows and NOT need the extra boot? When I DID need that extra boot when chain loading from Windows bootloader to the GRUB2 menu?

It seems to me I need a much deeper understanding of Boot managers and Boot loaders to really understand what is going on. If anyone else wants to shine some more explanation on this I'm all ears.

Cheers,

Flex