Dual Boot on Separate Hard Disk Drives

[Shadius]

Here's my output of the command:

shadius@shadius-phantom:~$ [ -d /sys/firmware/efi ] && echo "EFI boot on HDD" || echo "Legacy boot on HDD"
Legacy boot on HDD
shadius@shadius-phantom:~$

Does this mean that my Windows or Ubuntu was installed with BIOS mode and not UEFI mode?

[oldfred]

That says you have booted Ubuntu in BIOS/Legacy/CSM boot mode.
It does not say anything about Windows.

You can check in Windows.

Or if drive is gpt partitioned then Windows has to be UEFI as it only installs in UEFI boot mode from gpt partitioned drives and only in BIOS mode from the old MBR partitioning.

sudo parted -l

[Shadius]

Pre-installed Windows since Windows 8 released in 2012 is UEFI with gpt partitioning.
Windows only installs in UEFI boot mode to gpt partitioned drives.

Both Windows and Ubuntu can be installed by a user in the old BIOS/MBR configuration.
But UEFI & BIOS are not compatible. Once you start booting in one mode you cannot switch to other mode, or grub can only boot other installs in same boot mode.

If you used or have gpt partitioning on Ubuntu drive with an ESP - efi system partition (FAT32 with boot flag and at least 250MB) you can just reinstall grub when you boot live installer in UEFI mode. Easier with Boot-Repair. Otherwise, you need good backup of /home, perhaps /etc if you changed system settings, and list of installed applications to make it easy to reinstall them and then reinstall in UEFI boot mode.

Most suggest disconnecting Windows drive as Ubuntu's Ubiquity only installs grub to ESP on first drive, usually the windows drive. Most newer UEFI systems let you logically disconnect with UEFI drive settings and changing to disabled. Otherwise see this bug for workaround.

Posted work around to manually unmount & mount correct ESP during install #23 & #26
https://bugs.launchpad.net/ubuntu/+s...y/+bug/1396379

Or you can use Boot-Repair to reinstall grub after install. Grub installs to any drive, it is just Ubiquity that only installs to one drive, even though installer has options (that do not work in UEFI mode). Other distributions using grub2 let you choose drive and they work.

Shows first boot screen, so you know whether you have booted withUEFI or BIOS, although the choice in UEFI boot of flash drive usually says UEFI:XXXX for UEFI boot.
Shows installer with screen shots. Both BIOS purple accessibility screen & UEFI black grub menu screen
https://help.ubuntu.com/community/UEFI

My Ubuntu was recently upgraded from 18.04 to 20.04. I can't remember what mode it was installed in from since having 18.04. I haven't used it in a while.

How can I check? Was that the command that you said to use that gave the output of "Legacy on HDD"?

[Shadius]

That says you have booted Ubuntu in BIOS/Legacy/CSM boot mode.
It does not say anything about Windows.

You can check in Windows.

Or if drive is gpt partitioned then Windows has to be UEFI as it only installs in UEFI boot mode from gpt partitioned drives and only in BIOS mode from the old MBR partitioning.

sudo parted -l

Here's my output of

sudo parted -l

shadius@shadius-phantom:~$ sudo parted -l
[sudo] password for shadius: 
Model: ATA LITEONIT LCS-256 (scsi)
Disk /dev/sda: 256GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End    Size   Type     File system  Flags
 1      1049kB  608MB  607MB  primary  ntfs         boot
 2      608MB   256GB  255GB  primary  ntfs


Model: ATA Hitachi HDS72101 (scsi)
Disk /dev/sdb: 1000GB
Sector size (logical/physical): 512B/4096B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type      File system     Flags
 1      1049kB  983GB   983GB   primary   ext4            boot
 2      983GB   1000GB  17.1GB  extended
 5      983GB   1000GB  17.1GB  logical   linux-swap(v1)


shadius@shadius-phantom:~$

[tea for one]

According to the output, you do not have an EFI partition in your Windows drive, therefore it looks like you have Windows 10 in Legacy mode.

Can you confirm that you originally started with Windows 7 (or 8) and then upgraded in situ until you reached Windows 10?

[oldfred]

If you run Boot-Repair, DO NOT run the auto fix.
With two drives you want to only use the advanced mode for repairs.
In advanced mode you can choose an install and choose a drive on where to install boot loader.
https://sourceforge.net/p/boot-repair/home/Home/

You really want a Windows boot loader in MBR of Windows drive and grub boot loader in the MBR of the Ubuntu drive.
Grub only boots working Windows. And Windows turns fast start up which sets hibernation flag and then grub cannot boot Windows. You have to directly boot Windows, but if you have Windows boot loader in Windows drive you just need to select it in BIOS/UEFI one time boot and fix Windows then boot into grub again.

Best to also have Windows repair/recovery flash drive to fix Windows.
And of course you always need good current backups.

[tea for one]

@oldfred

I do not think that the OP needs boot-repair because there has been no discussion about non booting.
Now that it seems that both systems are in Legacy mode, there is the requirement in post 7 to use grub as the OS selection rather than boot options in the start up UEFI/BIOS screens.

If you use

sudo update-grub

within Ubuntu, that should pick up the Windows OS.

However, the OP wants Windows as a default with Ubuntu second and I don't know grub intimately enough to help with that request.

My preference would be to use Boot Device Options when powering up the PC but that has been rejected by the OP.

[oldfred]

If OP installs Windows boot loader to Windows drive, then he can set that as default in BIOS/UEFI.
Then whenever he/she wants Ubuntu, use the BIOS one time boot key, often f12 or f10 to choose to boot Ubuntu.
You can change default boot in grub also, but Windows 10 will keep turning on fast start up with updates and then grub will not boot Windows until fast start up turned off.

Multiple ways to change boot order in grub or default boot. Ubfan posted the one where you change order scripts are run.
You can also edit grub default either by number or description. Or manually copy 40_custom to 06_custom and add a Windows entry to that script. Grub processes scripts into grub.cfg in script number order XX_.

https://help.ubuntu.com/community/Gr...ecific_Entries

Even more examples:
https://help.ubuntu.com/community/Gr...ult.2BAC8-grub
find your windows entry in grub.cfg and copy to grub default like this Vista entry - If you edit your windows command use the edited copy as this must match the title exactly:
gedit /boot/grub/grub.cfg
and copy into grub_default here:
sudo -H gedit /etc/default/grub
GRUB_DEFAULT=0
change to comment # or delete old and add new :
#GRUB_DEFAULT=0
GRUB_DEFAULT="Windows Vista (on /dev/sda1)"
Then do:
sudo update-grub

[tea for one]

You can change default boot in grub also, but Windows 10 will keep turning on fast start up with updates and then grub will not boot Windows until fast start up turned off.

Thank you for the informative reply - much appreciated.

Therefore, when selecting the OS, there is a distinct advantage to use UEFI/BIOS Boot Device Options rather than grub when the systems are on separate drives.

UEFI firmware is not affected by OS upgrades, albeit Windows or Ubuntu.

[oldfred]

UEFI firmware is not affected by OS upgrades, albeit Windows or Ubuntu.

With BIOS that was true. BIOS and operating system were totally separate. But with BIOS updates, it reset to defaults and you often had to redo your settings.

But with UEFI some settings are reset & some are remembered. And operating system can modify some UEFI settings. Windows typically syncs BCD with UEFI boot options and that is why you often have to add another setting to BCS for Ubuntu.
Other settings are like BIOS and are only changed if you do an UEFI update. But both Windows and now Ubuntu (fwupd) may do UEFI update changing some settings back to defaults and causing issues.