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I tried to dual boot Pop!_OS 20.04 LTS. It already had Windows in it. So I created a partition and formatted it to ext4. After successful installation I tried to switch to Windows. Then I selected the partition with Windows in the boot menu but instead of windows, pop showed up. I tried to use the Windows Media Creation Tool to repair it, but while trying to boot into the pen drive's UEFI partition, I would still boot into Pop OS itself.

Running fdisk -l outputs:

Disk /dev/sda: 223.58 GiB, 240057409536 bytes, 468862128 sectors
Disk model: KINGSTON SA400S3
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc241bdfe

Device     Boot     Start       End   Sectors   Size Id Type
/dev/sda1  *      1026048 203700092 202674045  96.7G  7 HPFS/NTFS/exFAT
/dev/sda2       203700224 204797951   1097728   536M 27 Hidden NTFS WinRE
/dev/sda3       204800000 468858879 264058880 125.9G 83 Linux

The Boot Mode is set to: auto, so it should be able to boot both UEFI and legacy. And it prioritizes Legacy

efibootmgr -v outputs:

EFI variables are not supported on this system.

Did I screw up my BIOS or my EFI? How do I fix this ? Please give any possible solutions. Thanx!

Rishabh Raj
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  • Is your disk currently partitioned in GPT style, or is it MBR? Please run fdisk -l and edit the output into your question. Is your system configured to boot in native UEFI style, or legacy BIOS style, or does it accept both styles? If both which style is the preferred one? Does the boot menu include "Windows Boot Manager" in it? Could you also run efibootmgr -v as root in Pop_OS and edit the results into your question, please? – telcoM Apr 30 '21 at 16:07
  • suggest you read https://en.wikipedia.org/wiki/Power-on_self-test , https://en.wikipedia.org/wiki/BIOS , https://en.wikipedia.org/wiki/Master_boot_record , https://en.wikipedia.org/wiki/GUID_Partition_Table , https://en.wikipedia.org/wiki/UEFI . One will have the Answer. Read the others to understand that one. – waltinator Apr 30 '21 at 16:12
  • @telcoM, I just edited my post with more information, thank you so much for the quick reply! – Rishabh Raj Apr 30 '21 at 16:24
  • You have BIOS/MBR (msdos) type installs. Only one boot loader can be in MBR to boot. And grub will give option to boot Windows where Windows will not boot any Linux. But grub only boots working Windows. So if Windows fast start up is on (it turns it back on with updates), or it needs chkdsk grub will not boot it. With UEFI, you can just directly boot Windows, but with BIOS, you have to use your Windows repair/recovery disk to restore Windows boot loader, fix Windows, & then use Linux live installer to reinstall grub to MBR. And then sudo update-grub to add Windows to grub menu. – oldfred Apr 30 '21 at 17:46
  • @oldfred actually Pop!_OS uses systemd instead of grub. right? – Rishabh Raj Apr 30 '21 at 17:48
  • I have seen that default is SystemD boot, but you can install grub. Not sure with BIOS as I thought SystemD boot was UEFI only. https://en.wikipedia.org/wiki/Gummiboot_(software) So do you have grub or not? – oldfred Apr 30 '21 at 18:02
  • @oldfred i currently have systemD, but i will try and install grub, thanks for the reply – Rishabh Raj Apr 30 '21 at 18:04
  • Does this answer your question? "EFI variables are not supported on this system" – GAD3R Apr 30 '21 at 20:38

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Ok, I have follower the solution @olfred has mentioned.

I installed GRUB and checked if it would detect Windows 10 (generally, it should). At first, it didn't detect automatically, so I followed this: https://askubuntu.com/questions/197868/grub-does-not-detect-windows

I essentially unmounted and remounted the Windows partition, and installed and ran os-prober. That listed Windows 10 successfully, and I just had to do update-grub and it worked! I did a reboot and Windows showed up just as expected.

Rishabh Raj
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