[Post-Install] GRUB issue

[cookiemuncher]

I did a clean install when 25.04 appeared. I dual boot Kubuntu and Windows 11.
Booting into Kubuntu works just fine once setup. My problem comes after booting into Windows 11 and then later rebooting causes grub to be bypassed and boots back into Windows 11.
I then have to set Kubuntu as primary login in the CMOS setup again and can then enter grub with Kubuntu as primary and Windows as secondary.
Booting into Kubuntu repeatedly maintains the grub menu and setup.

[Qqmike]

I haven't used or dealt with Windows since about 2008.
Someone here will probably have a definitive answer for you.
Windows somehow is messing with your boot order.
I have heard that this can be caused by Windows Fast Startup.
Fast Startup causes Windows to not really fully shutdown.
People have reported that they disabled Fast Startup (somewhere in your Windows Control Panel, Power, maybe?)
You have already discovered how to use your UEFI boot order -- which is one solution to this issue.
And you discovered that re-booting works if you stay in Kubuntu. (Otherwise, sudo update-grub might be relevant to try.)

[TinyTim]

"Fast Startup causes Windows to not really fully shutdown."
You can hold the shift key down when shutting down windows and it should disable fast startup if you want to test it out. I think it is temporary however.

[cookiemuncher]

Did some testing. If I select Windows 11 from grub but not enter my login pin, but then immediately reboot, then I find the CMOS boot order has already been changed.
I have been using Kubuntu 24.10 until 25.05 was released and this problem did not occur with that version.
Secure boot is disabled. Fastboot is disabled. Both in CMOS.

[Qqmike]

Secure boot is disabled. Fastboot is disabled. Both in CMOS.

In BIOS, ok.
But then, also, disable the Fastboot in Windows OS, too? Maybe as an experiment?

[Qqmike]

Oh boy, I can't recall exactly what this is, I never used it, but there is a setting in one of the GRUB configuration files that -- I believe -- directs the PC to boot into the last OS it booted into. So, if you booted into Windows now, the next time you re-boot, GRUB will take you again to that Windows OS. Something like that. It's well known (but not by me! haha) Another shot in the dark. Suggesting that *somehow* that setting gets flicked 'on'? Frankly, it sounds crazy. But brainstorming. Some people suggest that it is Windows that messes with the UEFI boot order, but that also sounds a bit nuts.

[cookiemuncher]

In BIOS, ok.
But then, also, disable the Fastboot in Windows OS, too? Maybe as an experiment?

Disabling Fastboot in Windows also makes no difference.

[Qqmike]

I don't have 25.04. I have checked 22.04 and 24.04.
If you look in your /etc/default/grub file, by some strange chance, you do not have anything like the following, right? -->
GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true

(That would cause you to re-boot into the previously booted OS.)

You should have something like, simply, GRUB_DEFAULT=<some number, like 0, or 15, etc.>

[cookiemuncher]

I don't have 25.04. I have checked 22.04 and 24.04.
If you look in your /etc/default/grub file, by some strange chance, you do not have anything like the following, right? -->
GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true

(That would cause you to re-boot into the previously booted OS.)

You should have something like, simply, GRUB_DEFAULT=<some number, like 0, or 15, etc.>

[FONT=monospace][COLOR=#000000]GRUB_DEFAULT=0[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]GRUB_TIMEOUT_STYLE=hidden[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]GRUB_TIMEOUT=-1[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]GRUB_DISTRIBUTOR='Kubuntu'[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]GRUB_CMDLINE_LINUX_DEFAULT='quiet splash'[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]GRUB_CMDLINE_LINUX=""[/COLOR][COLOR=#000000] [/COLOR]

[COLOR=#000000]# If your computer has multiple operating systems installed, then you[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]# probably want to run os-prober. However, if your computer is a host[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]# for guest OSes installed via LVM or raw disk devices, running[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]# os-prober can cause damage to those guest OSes as it mounts[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]# filesystems to look for things.[/COLOR][COLOR=#000000] [/COLOR]
[COLOR=#000000]#GRUB_DISABLE_OS_PROBER=false[/COLOR][/FONT]

etc
etc...
​

All looks normal to me?

But this:

In summary: While Windows 11 doesn't directly change the BIOS boot order, certain events within the operating system can lead to unintentional alterations. You can always check and adjust the BIOS boot order through the BIOS setup utility.

Window pretends it doesn't see any bootable Linux partitions.

[claydoh]

https://linuxconfig.org/how-to-manag...ager%20entries

[cookiemuncher]

From Reddit:

https://www.reddit.com/r/Ubuntu/comm...ual/?rdt=44533

only once so far. windows did an update and somehow changed the boot order in bios? seems like magic but it really happened. i changed it back and haven't faced much issues

Windows can definitely change the contents of the BIOS boot order.
Happens to me each time I use Windows 11.
If this does no stop then I am going back to Kubuntu 24.10

Edit: re-enabling secure boot makes no difference.

[cookiemuncher]

Interesting reading

https://answers.microsoft.com/en-us/...b-1b8529a5f277

[claydoh]

With efibootmgr you can check your boot order, so it may be easier to see when it is being changed.
You can then change the order without booting to the BIOS, if you want.

In my experience, Bios/uefi firmware updates and major Windows updates very often change the boot order to Windows. But don't rule out a buggy BIOS firmware. An update may fix that, maybe/hopefully?

[cookiemuncher]

With efibootmgr you can check your boot order, so it may be easier to see when it is being changed.
You can then change the order without booting to the BIOS, if you want.

In my experience, Bios/uefi firmware updates and major Windows updates very often change the boot order to Windows. But don't rule out a buggy BIOS firmware. An update may fix that, maybe/hopefully?

Hi claydoh
If this is not affecting every user of (K)ubuntu then I am suspecting my BIOS

:~$ inxi -M
Machine:
Type: Desktop Mobo: TBYTE model: H510-VH serial: <superuser required>
UEFI: American Megatrends LLC. v: TEH51A01 date: 09/15/2022

EDIT: Reinstalled Kubuntu 24.10 and that has the same problem.

EDIT2: Installed Kubuntu 24.04 and that has the same problem.

[Qqmike]

I caught up reading all this.
I had also read here and there people claiming Windows was changing their BIOS boot order.
As I said above, sounds nuts but ... certainly something is amiss!
It does seem, though, to sort of It might point at your firmware UEFI-BIOS ->
You could google on that, your specific model/mobo.
Of course, nothing wrong with Megatrends, but maybe HOW the UEFI was implemented by the PC maker ... ?
As claydoh says, you can use sudo efibootmgr -o to change the boot order.