ThinkCenter UEFI hack

I have an old Lenovo ThinkCenter M91p, which I use to host BorgBackup repository and my music library with Navidrome.

Up untill last week I had NixOS installed on it with Legacy Boot. It worked fine for a while, but after an update, GRUB started to complain that it couldn’t find /grub/i386-pc/normal.mod file anymore. I suspect that it had to do something with me pairing it with BTRFS partition.

Without looking too much into it, I decided to finally take my time and setup NixOS with UEFI. After all, because of nix, I have to only deal with this once (right?).

I knew that ThinkCenters UEFI implementation did not follow standards. You can tell immediately by installing linux distribution of your choice and being greeted with this message after reboot:

Error 1962 “No Operating System Found”

After digging through “the internet” I have found a solution:

This is an error specific to some models of Lenovo computers. […] To fix this issue you need to add a custom EFI entry from within the live environment. You will name the custom entry “Windows Boot Manager” to trick the BIOS. Here’s an example on how to do that:

sudo efibootmgr -c \
  -d /dev/sda1 -p 1 \
  -L "Windows Boot Manager" \
  -l "\EFI\boot\grubx64.efi"

Interesting, should be fairly easy to add this to my config:

boot.loader.systemd-boot.extraInstallCommands =
let
  efimgr = "${pkgs.efibootmgr}/bin/efibootmgr";
  grep = "${pkgs.toybox}/bin/grep";
  new = "Windows Boot Manager";
  old = "Linux Boot Manager";
in
''
  echo "Applying 'ThinkCenter' hack"
  ${efimgr} --label "${old}" -B -q 2>/dev/null || echo "EFI entry '${old}' already deleted"
  if [ -z "$(${efimgr} | ${grep} "${new}")" ]; then
    echo "Creating '${new}' EFI entry"
    ${efimgr} --create -q \
        --label "${new}" \
        --loader '\EFI\systemd\systemd-bootx64.efi' \
        --disk ${cfg.device} \
        --part 1
  else
    echo "EFI entry '${new}' already exists"
  fi
'';

Lets see how long it takes before this breaks.