Re: Converted MBR to GPT and menu is gone, can't use grub-reboot either

[Michael D. Setzer II]

On 18 Feb 2023 at 10:21, Pascal Hambourg wrote:

Date sent:              Sat, 18 Feb 2023 10:21:34 +0100
Subject:                Re: Converted MBR to GPT and menu is 
gone, can't use grub-reboot
        either
To:                     Chandler <admin@genome.arizona.edu>, 
help-grub@gnu.org
From:                   Pascal Hambourg 
<pascal@plouf.fr.eu.org>
Organization:           Plouf !

> On 16/02/2023 at 14:49, Chandler wrote:
> > Hi all, I recently (like a month ago) upgraded one of our computers that
> > hadn't received any upgrades for like 2 years.  Afterwards, it wouldn't
> > boot.
> 
> What happened exactly at boot time ? Any error message ?
> 
> > I think it was because Grub2 got upgraded and no longer supported MBR?
> > (it's now version 2.06-3~deb11u5)
> > I read something along those lines, that I had to be using GPT now.  So
> 
> Nonsense. Of course GRUB still supports MBR/DOS.

Not sure if this might be issue, but I ran into an issue 
recently that had me very confused.
Had a Dell computer with Windows 10 that could not 
upgrade to 11 because it only had a 4th gen I3, and 11 
requires an 8th gen? So, decided to add Fedora 37 to 
drive. Booted from the install usb (didn't realize it 
booted from uefi), so when did the install it setup UEFI 
installation on the free space of drive. Everything went 
fine but on reboot, it showed the Fedora 37, but no 
reference to the windows 10?? Took a while to figure 
out, but only by using F12, and selecting legacy boot 
would it load the windows. 

So, what kind of upgrade did you do? In my case it was a 
installation of a new OS after shrinking the original 
Windows 10 to about 1/2 of disk. Didn't change disk from 
DOS to GPT, but it create a UEFI partition setup. Have 
been told the install looked at boot media type, and used 
that??

Was interesting...
So, don't know if you might have a disk with both legacy 
and UEFI setup??




> 
> > Except!  The boot menu is now gone and I actually just noticed now
> > that I'm trying to run memtest86.  I tried holding Shift while it
> > tries to boot, and also have tried tapping Esc, but neither of these
> > bring up the menu.
> 
> What is in /etc/default/grub ?
> 
> > Then I remembered I could use grub-reboot to boot into memtest86, but
> > not on this system apparently because when I tried that it told me this:
> > WARNING: Detected GRUB environment block on diskfilter device
> > Memory test (memtest86+, serial console 115200) will remain the default
> > boot entry until manually cleared with:
> >      grub-editenv /boot/grub/grubenv unset next_entry
> > 
> > I guess, it's because /boot is on a md device?
> 
> See grub-reboot manual. GRUB cannot write on RAID or LVM devices at boot 
> time to remove the next boot option in the GRUB environment block 
> /boot/grub/grubenv, so the option will be persistent.
> 


+------------------------------------------------------------+
 Michael D. Setzer II - Computer Science Instructor 
(Retired)     
 mailto:mikes@guam.net                            
 mailto:msetzerii@gmail.com
 Guam - Where America's Day Begins                        
 G4L Disk Imaging Project maintainer 
 http://sourceforge.net/projects/g4l/
+------------------------------------------------------------+