Dual boot ubuntu windows 10 - only boots into ubuntu - no boot selection menu

[yinnxbutu]

Which Windows iso do you have?
Does it boot in Legacy mode?
Have you backed up your personal data from both Windows and Ubuntu?

1) Windows 10
2) It is supposed to, but I can't get it to boot to Windows.
3) Yes, both are backed up.

[tea for one]

What actually happens when you boot the Windows installer?
Does it stall somewhere?

[yinnxbutu]

What actually happens when you boot the Windows installer?
Does it stall somewhere?

When you asked this I thought I'd go try it again. When I booted to the windows 10 flash drive it gave choices of what to do. I selected "troubleshoot repair boot problems" then it said it was not able to repair windows boot. Same result as before.
So I considered using the same flash drive to just reinstall windows. But before that I found another flash drive I made using macrium. I booted to it and it had a choice of repairing windows boot problems. So I ran it and it
fixed it, so now the computer boots straight into windows 10. However I guess that messed up Ubuntu because can't get back into grub. I rebooted several times with shift key, esc etc but so far it just goes straight to windows.
I think this is progress, I suppose I can just reinstall Ubuntu as I did before and have dual boot back again.

[tea for one]

Yes, I think that it is a bit of progress.
Previously, Grub wouldn't boot Windows because Windows was not in a bootable condition.
Now that you have successfully repaired Windows, good old Microsoft has resumed its dominance over the boot process.
I would now run boot-repair again and, fingers crossed, it will re-install Grub to the disk and recognise a working Windows.

[qyot27]

Windows has to have newer gpt partitioning for UEFI boot. Microsoft has required UEFI/gpt installs by vendors since release of Windows 8 in 2012. So all newer hardware is UEFI.

While OEMs may be required to use UEFI, an end user can still install Windows 10 (and presumably even Windows 11, but I don't know) in MBR mode. I did it unwittingly back in 2020(?) when I relented and installed Windows on my main setup, even though the existing Ubuntu installation was UEFI/GPT. Entirely separate boot drives too; grub could see the Windows partition, but couldn't boot from it; if I wanted to boot Windows, I had to use the motherboard's boot menu to do it.

The wrench in this was that I used VirtualBox to install Windows to the drive so it couldn't touch the existing Ubuntu installation. What I didn't realize at the time was that VirtualBox defaults to MBR, so that's how Windows installed itself.

Note conversion from MBR to gpt totally erases a drive. So backups required.

Backups are of course recommended, but Windows 10 does have a utility to do an in-place conversion from MBR to GPT post-install. I used it to fix that above situation so that my Arc A770 could actually be configured properly (because settings related to turning on Resizeable BAR require UEFI, but setting it to UEFI only caused Windows to stop booting, which made me finally realize what had happened when I'd installed it). Afterwards Grub could boot either OS without an issue...until a couple weeks ago. I'm not sure if it was a Windows update, or the installer for 24.10, but I'm back to needing to use the motherboard's boot menu to get into Windows.

[yinnxbutu]

Yes, I think that it is a bit of progress.
Previously, Grub wouldn't boot Windows because Windows was not in a bootable condition.
Now that you have successfully repaired Windows, good old Microsoft has resumed its dominance over the boot process.
I would now run boot-repair again and, fingers crossed, it will re-install Grub to the disk and recognise a working Windows.

Yes, I think that will work, but now I'm thinking of just using a separate computer for Ubuntu and avoid dual boot issues.

Thanks for all your help and the others that contributed too, I never would have figured this out by myself.

[tea for one]

but now I'm thinking of just using a separate computer for Ubuntu and avoid dual boot issues

Yes, fully agree.

If you can possibly manage it, have one OS per computer
If you absolutely must have more than one OS per computer, at least have one OS per disk
If you absolutely insist on having more than one OS per disk, understand everything written on this page

The above quotation was slavishly copied from the Recommendations (scroll towards end) here:-
https://www.happyassassin.net/posts/...lly-work-then/
It's worth a look, especially for PC users who like to experiment (i.e. dilettante (myself) rather than professional)

[oldfred]

I had a working Windows/Ubuntu dual boot on one drive working well.
Then hardware issues & Windows corruption erased my working Ubuntu. Gave up on dual boot on one internal drive & now use an external SSD with Ubuntu on Windows laptop. Actually external SSD is a copy/backup of my desktop install. So far that has worked much better.

Have had no issues with multiple installs of Ubuntu & other Linux systems on same drive other than managing grub & boot order. I just have to keep main working LTS install as default boot & add others to its grub menu.