Kubuntu does not boot after installation

[Babis]

I have migrate from Opensuse to Kubuntu. In Opensuse i have different partition for /home and i want to keep it. So during the installation i keep the /home and swap partition and delete the rest. From what is left i make an EFI partition of 35M and the rest i set it as ext4 for /. The installation finish without a problem but at boot time it shows GRUB and a cursor blinking, by pressing any key a message "This is not a bootable disk. Please insert a bootable floppy and press any key to try again ..."

Thinking that i have to convert my disk to EFI i follow the instructions from here "https://askubuntu.com/questions/84501/how-can-i-change-convert-a-ubuntu-mbr-drive-to-a-gpt-and-make-ubuntu-boot-from" and reinstall it but the result is the same

Thank you in advance for any help

[claydoh]

35 Mb is probably going to be too small, but that would probably cause the installation to fail. But it might cause problems later on.

Have you changed the boot settings in your Bios? I wonder if it is trying to boot the last OS, which is no longer there.
Make sure you have the correct OS/drive selected, and that you do have EFI enabled if it wasn't before.

[Babis]

35M was the suggestion from the installer.
If i change the bios setting from legacy to UEFI then rhe disk is not any more visible from the BIOS.
I forgot to mention that my disk is SSD, if that change something.

[Snowhog]

What Make/Model is your PC? Did you get it new, and if so, what year?

[Babis]

Its an a gigabyte motherboard with I7 processor and nvidia graphics card. I made it from parts around 6 years ago.

[claydoh]

35M was the suggestion from the installer.
If i change the bios setting from legacy to UEFI then rhe disk is not any more visible from the BIOS.
I forgot to mention that my disk is SSD, if that change something.

I think at this point, it might be better to keep the UEFI enabled, then reinstall, and use a bit larger boot partition -- ~100 to 200Mb will be more than enough I think, just to be safe.
It might be worthwhile to boot the installer to a live OS session, and maker sure your old /home is still OK, and back that up if possible.

[jglen490]

35MB on a single OS install should be O.K. The actual used size of my ESP is

/dev/nvme0n1p1 93M 5.2M 88M 6% /boot/efi

You can use

efibootmgr -v

to see what is in your ESP. Also, it's possible to accidentally select the wrong boot file location in the partitioning page of the installer.

[Qqmike]

And you do still have to mark the EFI as a special partition, right? I thought you had to set a boot flag on it, which in UEFI doesn't mean "boot" but it means ESP. Maybe that is why it's not seeing any bootable device?

[Babis]

Happy new year and thank you for the support

Before i have enough coffee i give it another try, but this time i let it to do the partitioning (no coffee). Now it works perfect except that all my data gone.

Thank you again, now let me find a dark place to hide and cry.

[jglen490]

Qqmike Yes, the EFI partition has to be marked as an ESP; however, the partitioning process in the installer has an "ESP" option which takes care of all that. If one simply makes a fat32 partition, and not an ESP partition, then the flags are not set.

[Qqmike]

Ah, jglen490, that's what I missed or got confused on. Old school: I always manually set the boot flag (e.g., when using gparted). But somehow I thought I saw or remembered this being done automatically by the installer. Scrambled brains! That confirms & clears it up. Thanks.

[jglen490]

You're welcome!