Install a new linux without changing efi order [solved]

I have already KDE-Neon on my new PC, but I’d like to install Kubuntu as well, as a secondary SO. I have a gpt disk, with efi partition.
However I don’t want that Kubuntu became the main SO of my PC, from which it boots.
I know that with Efibootmgr I should be able to restore - so to say- KDE Neon as “main” SO, but I have a previous experience with that application not exactly happy.
What way could you suggest me?
Thank you!

OK if I’m understanding you correctly you want Kubuntu as the second boot option, right?

If so then just either use the partition manager that’s on the live ISO for Kubuntu to shrink your KDE_Neon partition and then install Kubuntu in the now empty space, or simply run the Kubuntu installer from It’s live ISO and when you get to Partitions select install along side and then select your KDE-Neon partition and you will see it present you with what the drive will look like after install.

Once you have that done and installed I’d boot into Kubuntu and at least do any updates that there might be, then boot into your bios and change the boot order to make Neon the first in the list.

Depends on a lot of stuff.

Will you create another boot partition for the second installation or share one?

If one partition, how will you control updates not “taking over” the grub and putting whatever you are updating first again?

If separate boot partitions, can you not set it in your bios?

My recommendation is to use a completely different device (not just different partition) if you do not know 100% what you are doing.
That way you minimize the problems that WILL arise because mark my words, you will get problems, not complicated, but frustrating if you do not know what is going on.

Thank you both. I know very well that a multiboot is possible, and several times in the past I have successfully set it (windows + kubuntu + other linux distro).
Recently (with a bios very similar to the one of my new pc, perhaps identical) I had a real nightmare trying to re-adjust the efi order with both bios and Efibootmgr.
So I am now very (maybe too) cautious to act something with efi …

My aim this morning i.g. was to install kubuntu without install its bootmanager (I chose to install the bootmanager inside the kubuntu partition), but something gone wrong.

While kubuntu is still using the ubiquity installer, you can tell it not to install a boot loader. Choose “Try Kubuntu” then in a konsole:

ubiquity -b


I have installed Kubuntu on the right partition, using ubiquity -b, no errors in installing. I can boot from KDE-Neon, as expected.
But update-grub doesn’t recognize the new distro.
The error message in update-grub is:

Memtest86+ needs a 16-bit boot, that is not available on EFI, exiting
Found pcmemtest 64bit EFI image: /@/boot/pcmemtestx64.efi
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.

What should I do?


I found the answer here:

os-prober has been disabled by default, you need to uncomment/add


to `/etc/default/grub` and run `sudo update-grub`.

Done! And now Kubuntu is recognized.

NEVER install the boot manager in the OS partition, ALWAYS use the existing boot partition IF you are installing multiple OS on the same drive. IF you are installing on multiple drives then the OS media should automatically create a new boot partition on the new drive.

A side note about OS-Prober:

On some installs when using BTRFS you must install os-prober-btrfs instead of os-prober. I know you got it working just letting you know for the future if you should run across uncommenting the one line still doesn’t work.

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