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As the title says I'd like to install Ubuntu 20.04 LTS on my computer alongside Windows 10. My system is UEFI (non CSM) and both disks partitioned GPT. Secure Boot is disable, thought, I read here newer versions of Ubuntu don't have a problem with it and I was wondering if I may enable it after (or even before) the installation. Windows's Fast Start Up is also disabled.

Pre-installation: System Backup and Bootable USB

I've backed up my personal documents in a pendrive. However, I couldn't create a system image in an external drive since I don't have a DD with that much space. The only Windows's backups are the Recovery partition HP made and Windows RE.

Do I need an extra backup specifically for the EFI partition or it's included in Windows RE or HP Recovery? If not, should I consider buying an external drive with that amount of capacity?

I used Rufus 3.13 to create a bootable USB with the ISO image fro the official Ubuntu with a GPT partition scheme and a FAT 32 file system format.

Partitions

This is how my disks and partitions look right now (Disk 0 is the HDD and Disk 1 th SSD):

Disks and Partitions

My intention is to install all that has to do with Ubuntu in the non allocated space. I'm imagining that, if something like that could be posible, I might be able to delete those partitions (independent from the Windows's ones) and pretend nothing happened there. The unallocated space size that is shown in the screenshot can be more than 100 GB if needed. Comments said I was using and outdated partitioning scheme, so I will check that again.

Is it possible to create a new ESP on the free space and somehow choosing between them? I'm confused about if GRUB/Windows Boot Manager are themselves a Boot Menu from which I choose the OSes, if they are EFI files that I choose one of them to boot from in the UEFI Boot Menu, if one of them contains the other...

It is possible to create a new ESP on the free space. In that case, UEFI Boot Menu will ask to choose between GRUB and Windows Boot Manager. GRUB will ask to chose between Ubuntu and Windows. This is still not clear to me. The UEFI Boot Menu let me chose from 2 ESP. Choosing Windows's one will boot Windows, of course, but choosing Ubuntu's one will open GRUB, a mystical entity whom possess both Ubuntu's and Window's EFI's files.

Since GRUB somehow has information about my Window's ESP (it can boot it), doesn't deleting the Ubuntu partition will damage Windows?

Considering I create a new EFI partition on the HDD, what should I select as Boot Loader: the whole disk or the ESP?

It doesn't matters because it doesn't works.

I don't mind of having to enter UEFI Boot Manager (or whatever it will turn to be) each time I turn on my PC because it will automatically boot Windows. I'd like to prioritise not having any troubles with my current OS and, if there are, getting back to normal the easiest ways possible.

I apologise if this post is sort of duplicate. I read many other posts, answers and internet entries but, since my knowledge on this topic is null, I might have not been able to take profit of them. Thanks in advance.

Gilgamesh
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  • Is there a reason that you do not unplug your Windows drive and then install Ubuntu where planned. You won't harm Windows if it is not there. After install Boot the Ubuntu drive and sudo update-grub to add Windows to the grub menu. You have things covered with a UEFI install by using Rufus with GPT/UEFI options. – C.S.Cameron Dec 22 '20 at 08:57
  • It's a laptop, I forgot to mention that. If it wouldn't be the case, you will be suggesting to have 2 ESP's one en each drive, right? Hypotetically in that scenario, if I deleted the Ubuntu partition, wouldn't Windows's boot be compromised? After all, the GRUB's update included it into their menu. – Gilgamesh Dec 22 '20 at 09:24
  • An ESP on each drive is a good solution in my opinion especially if you want to minimise the risk to Windows 10. If your firmware is set to boot disk 0 you will have grub with the choice of OS’s. If you boot disk 1 you will go straight to Windows 10. The partitioning link is very old and based on MBR. There are plenty of advantages of a single partition for root and home. A Swap file is default these days so you don’t need to worry about that. – PonJar Dec 22 '20 at 09:57
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    Many people use Full install USB drives. I have been using them for many years. Just about all Full install USB drives have grub on the drive. Nothing bad happens to Windows when you unplug them. Windows is put on Ubuntu's bootloader, Windows is not modified. Much safer than messing with the Windows drive. – C.S.Cameron Dec 22 '20 at 11:56
  • If you do not unplug or in UEFI settings, temporarily disable the Windows drive, Ubuntu's Ubiquity installer will install grub into the Windows drive's ESP. That works without issue, but many want Ubuntu boot files on Ubuntu drive. If only using 100GB, use just / (root) (and ESP if desired). Only one ESP per drive, allowed. Desktops typically do not need /boot, and swap is now a swap file not a partition. Ubuntu install will make it first in UEFI boot order, but you can easily change back to Windows if desired in UEFI or in Ubuntu with efibootmgr. – oldfred Dec 22 '20 at 16:32
  • @oldfred, I didn't found an option to disable my Windows's Drive in the UEFI settings. Choosing the new ESP I created (or the whole disk?) doesn't matters at all to Ubuntu? It will keep installing GRUB where it wants (i.e Windows's ESP)? – Gilgamesh Dec 22 '20 at 19:13
  • I use gparted and create an ESP of about 500GB if on a larger drive. If a small flash drive (32 or 64GB) with full install, I use 100MB. Only the Ubiquity installer automatically chooses an ESP on the first drive. Reinstall of grub or other distributions using grub2 let you choose which drive's ESP to use. Some more details: https://askubuntu.com/questions/1296065/dual-booting-w10-ubuntu-with-2-separate-ssds-in-uefi-mode/1296153#1296153 – oldfred Dec 22 '20 at 19:48
  • @oldfred, I don't understand... isn't /boot the location where I mount the EFI partition? If I'm going to create one, how it isn't necessary? – Gilgamesh Dec 22 '20 at 19:48
  • Do not confuse a /boot Linux partition that must be ext4 (or other Linux format) and an ESP - efi system partition that must be FAT32 with boot/esp flags. An ESP has some of grub2's boot files and loads the rest of grub & kernel from /boot folder (or partition). SystemD boot does put more of files in the ESP, but then does not use grub2 for booting. – oldfred Dec 22 '20 at 19:56
  • @oldfred, Oh.. OK, thanks. Supposing I'm not able to logically disconnect my drive, when you say "first drive" ,do you mean by their number? The HDD will be the first drive? – Gilgamesh Dec 22 '20 at 20:12
  • Let us continue this discussion in chat. – Gilgamesh Dec 22 '20 at 21:10

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