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Last July, as a complete Linux noob, I bought a refurbished Dell e7470 with Windows 10 pro pre-installed. I followed instructions in this video (cued to disk partition steps) to install Pop_OS 20.04 to dual-boot with Windows 10: Pop!_OS 19.10 - Setting up a Dual Boot with Windows 10. It went well. Now I am thinking about removing Windows, and I am looking at my disk partitions to see what can be removed. Here is screenshot from GNOME Disks while running Pop:

GNOME Disks

I do not understand why the video had me create a new EFI partition (sda5) instead of using the ESP (sda1) that was pre-installed with Windows. I am wondering if that may cause problems, but, more importantly, whether I can use Disks to remove the Windows OS (sda3) as well as the ESP (sda1), recovery partition (sda4) and "Microsoft Reserved" (sda2). I do not want to do something wrong and end up with an un-bootable computer.

In case it is helpful, here is the output from efibootmgr:

steve@pop-os:~$ sudo efibootmgr
BootCurrent: 0003
Timeout: 2 seconds
BootOrder: 0003,0000,0001,0004
Boot0000* Windows Boot Manager
Boot0001* UEFI: SK hynix SC311 SATA 512GB, Partition 1
Boot0002* Pop!_OS 20.04 LTS
Boot0003* Pop!_OS 20.04 LTS
Boot0004* Linux Firmware Updater

Boot0000 and Boot0001 seem to be the same -- Partition 1, as are Boot0002 and Boot0003 (partition 5).

I would like to know:

  1. Is this 2-EFI-partition setup acceptable?
  2. How would I safely (and as completely as possible) remove Windows 10?
  3. Will my system be bootable without ESP, ie, will it use Partition 5 which says it mounts at /boot/efi?
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  • Most UEFI only support one ESP per device/drive. But you can have more than one FAT32 and sometimes that works with grub. But Pop does not use grub. It may be because the default Windows ESP was small 100MB, I believe Microsoft now makes it somewhat larger. But Pop uses SystemD boot and that puts more files into the ESP and it may need to be larger. You show a larger ESP, so I would expect it to be ok. – oldfred Mar 12 at 21:55
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I believe this is an example of tutorials offering slightly misleading information. There's a number of reasons this happens, sometimes the author wants to be certain their advice will work in all situations, sometimes the author themselves hasn't quite understood their own topic.

You do not want, and generally shouldn't have two EFI (ESP) partitions on one drive.

If you are certain you wish to completely irreversibly1 remove windows then you can:

  1. Remove all partitions associated with windows except EFI.
  2. Delete the Windows boot loader from the EFI partition.

If you are just installing Pop OS as a fresh install

You can just wipe the drive and start with a fresh partition table. Don't even bother saving UEFI, just start again.

If you are converting an existing Pop OS installation

Be more careful. Keep your Pop OS bootloader files installed on EFI. If a tutorial is telling you to create a new EFI partition, then you can follow it but make sure that you:

  • Installed your bootloader to your new EFI partition
  • Remove your old EFI partition so you are left with only one.

  1. To re-install Windows you will need to get a copy of a windows installer. This can often cost you a brand new licence because OEM versions don't provide install CDs.
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  • Thank you. I want to be clear about "If you are converting an existing Pop OS installation" since that describes my situation. Currently, Pop boots from Partition 5 and Windows, from Partition 1, based on my interpretation of efibootmgr -v which returns: ...Boot0000* Windows Boot Manager HD(1,GPT,3c...Boot0003* Pop!_OS 20.04 LTS HD(5,GPT,0e... So are you saying that I can delete ESP Partition 1 (as shown in my Disks screenshot above) since that is the EFI that Windows boots from, and that keeping Partition 5 will keep Pop OS in a bootable state? – Steve Mar 13 at 16:48
  • If partition 5 is an ESP (EFI) partition then yes. The ESP partition holds the boot loader which tells your machine what to do when it boots. Usually you only need one as multiple bootloaders can be placed on in the same partition. – Philip Couling Mar 13 at 17:08
  • Does Boot0003* Pop!_OS 20.04 LTS HD(5, GPT,... confirm that Partition 5 is, in fact, an ESP? I am assuming that the '5' after the open parenthesis identifies the partition. Also, Disks shows that Partition 5 is mounted at /boot/efi – Steve Mar 13 at 17:38
  • Windows OEM keys can (usually) be retrieved from the bios, Windows Command Prompt: wmic path softwarelicensingservice get OA3xOriginalProductKey Unix Shell: sudo cat /sys/firmware/acpi/tables/MSDM – rfmodulator Mar 20 at 16:29
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I was able to use GNOME Disks to remove all the Windows10-relevant partitions. My system booted into Pop without any problem. Unfortunately, this left a large unallocated area at the start of my SSD.

GNOME Disks was not able to adjust that (it can resize partitions with contiguous unallocated space, but it cannot move them), so I booted using a Pop_OS installation USB and used Gparted to resize/move partitions. I restarted and booted into Pop just fine. The only oddity was that my 3 contiguous partitions -- ESP, swap, Linux system -- were labeled as partitions 5, 6, 7.

I could have (and perhaps should have) left it at that, but it bothered me that my 3 partitions were not 1, 2, 3. After a quick internet search, I used sudo gdisk /dev/sda with the s (sort) and w (write) commands. My partitions were now 1,2, and 3.

I booted into Pop again without issue, but efibootmgr showed that my system was booting with a generic bootnum entry (0006): UEFI: SK hynix SC311 SATA 512GB, Partition 1. This pointed to a different loader, EFI\boot\bootx64.efi, not \EFI\systemd\systemd-bootx64.efi (although it worked fine).

I used efiboomgr to create new bootnum entries (it started with the unused Boot0000) and wrote meaningful labels and correct paths to their loaders*. I deactivated the old bootnum entries that pointed to non-existent partition 5. (I could remove them, but they seem a good way to remind me about what I did here.)

* This is plural because I also recreated "Linux Firmware Updater" since that had been in my boot order prior to all these changes.

EDIT/UPDATE: When I ran gdisk and s (sort) there was a warning about possibly having to edit /etc/fstab. Being a Linux newbie, I decided to look at that file and read about its significance. I then made one small change. I changed the last field (fsck pass) of my system partition to "1". It had previously been set to "0" (no fsck; I am not sure why it was set that way).

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