112 lines
2.2 KiB
Markdown
112 lines
2.2 KiB
Markdown
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# EFI notes
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## Dual Boot
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We can use the EFI `NextBoot` feature to signal that the system should boot the 2nd OS.
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For initial setup, find the 2nd OS boot entry:
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```sh
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PS C:\Users\pleb\Documents\windows-scripts> PowerShell.exe -ExecutionPolicy Bypass -File .\List-BootEntries.ps1
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Found Boot0000
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Found Boot0002
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```
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Hard-code the boot entry in the `Set-BootNext.ps1` script:
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```powershell
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# NixOS boot entry ID
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$NixOSBootEntryID = "0002"
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```
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Then whenever you want to run NixOS, run the script:
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```sh
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PowerShell.exe -ExecutionPolicy Bypass -File \Users\pleb\Documents\windows-scripts\Set-BootNext.ps1
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```
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## EFI Recovery
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Sometimes Windows Update will trample the EFI boot entry for NixOS.
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## Linux
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* Boot into a NixOS live environment (USB or CD).
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* Mount your NixOS root partition and the ESP (EFI System Partition):
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```sh
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mount /dev/nvme0n1p4 /mnt
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mount /dev/nvme0n1p1 /mnt/boot
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```
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* Chroot into your NixOS installation:
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```sh
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nixos-enter --root /mnt
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```
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* Manually reinstall the bootloader:
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```sh
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bootctl install --path /boot
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```
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* Exit the chroot environment:
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```sh
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exit
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```
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* Unmount the partitions:
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```sh
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umount /mnt/boot
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umount /mnt
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```
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8. Ensure the boot order is to your satisfaction
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```sh
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efibootmgr -v
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efibootmgr -o XXXX,YYYY
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```
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9. Reboot your system.
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By following these steps, you should be able to recover your NixOS boot option if it disappears after a Windows update.
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## Windows
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In the unlikely scenario that the Windows boot entry is removed, here's how to recover from that:
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* Mount the EFI System Partition if it's not already mounted:
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```sh
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mount /dev/nvme0n1p1 /mnt/boot
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```
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(Replace nvme0n1p1 with the correct partition if different)
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* Verify that the Windows bootloader files exist:
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```sh
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ls /mnt/boot/EFI/Microsoft/Boot/
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```
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You should see a file named `bootmgfw.efi`.
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* If the files are present, you can create a new boot entry for Windows using `efibootmgr`:
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```sh
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efibootmgr -c -d /dev/nvme0n1 -p 1 -L "Windows" -l '\EFI\Microsoft\Boot\bootmgfw.efi'
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```
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This command creates a new boot entry labeled "Windows" that points to the Windows bootloader file.
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* Verify that the new entry was created:
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```sh
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efibootmgr -v
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```
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