I have a Dell XPS 15 9560 and I have been using Windows 10 and Ubuntu as a dual-boot system for quite a while. When I heard about the Qubes OS I decided to give it a try. I made some free space on my disk and tried to install it alongside the other two systems. The thing is, I had to switch from UEFI to legacy mode in order to install Qubes OS. I remember when I was creating partitions for Qubes OS, I didn't make it use the existing /boot partition, I made a new /boot. After the installation, the original Ubuntu grub disappeared and there is only Qubes OS grub. I tried to add Windows menu entry to the new grub but that didn't worssk, sos I used a Windows repair drive and did bootrec /fixmbr and bootrec /fixboot. After that, even thess new grub disappeared and now it is just "MISSING OPERATING SYSTEM."

I used boot-repair and generated a boot-info

I know this is a complex problem but I am really hoping someone can help me with this. Thank you all in advance!

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    You cannot mix BIOS & UEFI boot on one drive. And best to not mix even if installed on separate drives as you can only dual boot from UEFI boot menu, not from grub. It also looks like Windows is hibernated & You have encrypted Ubuntu install, and did not decrypted it, so Boot-Repair never saw it. And now bios_grub used only for BIOS boot and /boot are mixed up? this is an Ubuntu question & answer site, so cannot help on issues with other systems. – oldfred Jul 8 at 15:21
  • @oldfred Thank you for your reply. Right now I think the problem is that the UEFI can't detect the EFI partition anymore even it is perfectly fine(I have checked the files) so I cannot add boot entries in UEFI setup. – Colson Xu Jul 8 at 15:26

I found a solution using windows pe system. I used DiskGenius to delete the existing ESP partition and built a new one using the tool that comes with it. Then I rebuilt the bootloader using a special script that also came with the pe system. I know it doesn't sound helpful, it is because it was a Chinese pe system and the script doesn't have a name and is not available here in the US. The idea is just to rebuild the ESP partition.

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    With Ubuntu (or most Linux), you can just create or recreate an ESP - efi system partition as FAT32 with boot flag and/or esp flag to make it the ESP. You can restore .efi files if backed up. And then use efibootmgr to create UEFI boot entries, if system already installed and files in ESP. For Ubuntu you can also totally reinstall grub2 in UEFI mode which adds files into ESP & uses efibootmgr to add new entry into UEFI. I believe but do not know that Windows has same tools, your script probably just automates it, somewhat like Boot-Repair does for Linux. – oldfred Jul 8 at 16:41
  • @oldfred I guess yes. Boot-repair never worked for me and this script only restored my access to Windows (which is good enough) I have decided to do a full disk clean reinstall just because I have messed up the partitions and the boot entry too much lol. Glad I had everything backed up. – Colson Xu Jul 8 at 16:53

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