how Multiboot: Windows + Ubuntu 18.04 + Ubuntu 20.04


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Aug 29, 2020
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I had already installation of DualBoot : Win10 + Kubuntu 18.04,
It was 2 years ago, so I don't exactly remember how was it, but probably first was Windows and then Ubuntu created grub bootloader, ( used EFI ? )
I use also LVM partitions in Linux.

Now I would like to add new installation of Ubuntu 20.04 and here I am stucked.
Kubuntu Installer asking for bootloader device and I am not sure what is correct next steps to avoid break my previous boot setup.
With new install destination device for new 20.04 I already created PV and VG01, that is not the problem, issue is bootloader.
Any idea please ? I would like to have all 3 installations : Win, 18.04 and 20.04

Another question is how to save my current bootloader / grub conf.

Here is screenshot from installation option:

And here is my current boot setup

And here are my devices>
Device Start End Sectors SizeType
/dev/nvme0n1p1 2048 1023999 1021952 499M Windows recovery environment
/dev/nvme0n1p2 1024000 1228799 204800 100M EFI System
/dev/nvme0n1p3 1228800 1261567 32768 16M Microsoft reserved
/dev/nvme0n1p4 1261568 817877051 816615484 389,4G Microsoft basic data
/dev/nvme0n1p5 817879040 819199999 1320960 645M Windows recovery environment
/dev/nvme0n1p6 819202048 903088127 83886080 40G Linux filesystem
/dev/nvme0n1p7 903088128 919865343 16777216 8G Linux swap
/dev/nvme0n1p8 919865344 1338396671 418531328 199,6G Microsoft basic data
/dev/nvme0n1p9 1338396672 1645596671 307200000 146,5G Linux filesystem
/dev/nvme0n1p10 1645596672 2669596671 1024000000 488,3G Linux filesystem
/dev/nvme0n1p11 2669596672 2874396671 204800000 97,7G Linux filesystem
/dev/nvme0n1p12 2874396672 3079196671 204800000 97,7G Linux filesystem
/dev/nvme0n1p13 3079196672 3283996671 204800000 97,7G Linux LVM
/dev/nvme0n1p14 3283996672 3509276671 225280000 107,4G Linux LVM

I also found that grub cfg configuration for my old setup is in /boot/grub/grub.cfg,
but in the head is below notice

*"It is automatically generated by grub-mkconfig using templates
from /etc/grub.d and settings from /etc/default/grub"*

and when I look in /etc/grub.d/ there are some templates, but looks not reflected my current setup, so I dont know how works this auto-gen grub. (e.g. i dont have any Xen in my current boot menu, but here it is )

ls /etc/grub.d/
00_header 10_linux 20_memtest86+ 30_uefi-firmware 41_custom
05_debian_theme 20_linux_xen 30_os-prober 40_custom README


Install to /dev/nvme0n1 (or /dev/nvme0 if it's available). This will install it as the default bootloader (and it will recognize your other OSes).
Anytime that you install a new Linux distro just run:

sudo update-grub

Running that will find the newer distro.

Don't edit the grub.cfg whatever you do.
There's a safer way to add a menu entry 'if' you have to.
did you mean run update-grub on older distro ? if I have already updated grub (bootloader) with new distro ?

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