Booting to Grub (1.99) menu after upgrade to Fedora 31 - cannot boot

I upgraded my system from Fedora 29 to Fedora 30, then to Fedora 31. Although the OS version was Fedora 31, the kernel was still listed as fc29. I used the recommended script to switch to blcs and grub2.

After a kernel update today (vmlinuz-5.4.19-200.fc31_x86_64), when I boot the system it goes to the grub promp with Grub 1.99 at the top.

I have tried to boot from the grub menu with

set root=(hd0,gpt1)
linux (hdo,gpt1)/boot/vmlinuz-5.4.19-200.fc31_x86_64
boot

But, the system won’t boot and I get an error:
not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

Is there way to switch to grub2 from the grub1.99 menu?

It’s (hd + letter o). Try number 0.

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Hi, @jcruks, and welcome to Ask Fedora!

It looks like you need to update your grub installation. It’s quite easy to do, but there are some caveats. First of all, you need to know for sure if you’re using BIOS/legacy boot or UEFI boot on your system – grub is installed differently depending on the above.

If you unsure how to proceed – I suggest verifying first here before making any changes.

Most of the info you need to do it is here:

https://docs.fedoraproject.org/en-US/quick-docs/bootloading-with-grub2

If you’re able to boot to your installation using @vits95 correction, you can use this command to determine which boot type is in use on your system:

test -d /sys/firmware/efi && echo EFI || echo Legacy

Then you can reinstall/update grub bootloader from your running system using instructions from Installing GRUB sections from the linked doc.

If you’re unable to boot – you can still do the same from Fedora Live CD / USB, there’s a section for this too:

https://docs.fedoraproject.org/en-US/quick-docs/bootloading-with-grub2/#restoring-bootloader-using-live-disk

Again, the commands will be a bit different depending on boot type you’re using.

If you need additional info and clarifications – please ask.

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I think it’s this bug. There is a workaround you can try, and if it works then double check this is BIOS firmware (virtually certain it is).

https://fedoraproject.org/wiki/Common_F30_bugs#GRUB_boot_menu_is_not_populated_after_an_upgrade

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I was able to get things fixed by booting from a live DVD, chrooting my existing filesystem and installing grub2 to the boot partition. After a kernel upgrade through DNF, everything is now working as expected.

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