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

[Chandler]

The upgrade was from Debian 10 to 11.  That's the only OS installed.
The BIOS is in Legacy mode and if I change it to UEFI mode then it can't
find any boot devices.

Pascal Hambourg wrote on 2/18/23 2:21 AM:
> What happened exactly at boot time ? Any error message ?
It was the standard BIOS message of "no boot device found, press F1 to
retry or F2 to enter setup" or along those lines.

> Nonsense. Of course GRUB still supports MBR/DOS.
Noted

> What is in /etc/default/grub ?
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX=""
GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS1,115200n8 ecrc=on
intel_idle.max_cstate=2 iommu=off log_buf_len=1024M processor.max_cstate=2"
GRUB_GFXMODE=1024x768

> 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.
I see.  Is it much more difficult to write to md device when it can
already read from it, then?

Any other options for temporarily booting one of the other menu entries?

Booting the memtest86.ISO remotely through the iKVM is quite an ordeal,
and seems to be buggy when the BIOS window changes size or refreshes.  I
can get it to work by mounting the ISO through the iKVM and then using
the SOL for the rest of the interactions with the computer so that works
at least...

but I don't know what I would do if I ever needed to boot the previous
kernel or a recovery mode...