[root@fnord:/]# NIXOS_INSTALL_BOOTLOADER=1 /nix/var/nix/profiles/system/bin/switch-to-configuration boot
updating GRUB 2 menu...
installing the GRUB 2 EFI boot loader into /boot...
Installing for x86_64-efi platform.
Installation finished. No error reported.

[root@fnord:/]# /nix/store/31drz5w4nvvgazjgyb9g753j4b8fkc8y-efibootmgr-17/bin/efibootmgr -v
BootCurrent: 001C
Timeout: 0 seconds
BootOrder: 0001,001A,0018,0019,001B,001C,0000,001D,001E,001F
Boot0000* Windows Boot Manager  HD(1,GPT,dc01f4ad-4985-4c70-901d-5699dbf2cce6,0x800,0xff000)/File(\EFI\Microsoft\Boot\bootmgfw.efi)WINDOWS.........x...B.C.D.O.B.J.E.C.T.=.{.9.d.e.a.8.6.2.c.-.5.c.d.d.-.4.e.7.0.-.a.c.c.1.-.f.3.2.b.3.4.4.d.4.7.9.5.}....................
Boot0001* NixOS-boot    HD(1,GPT,dc01f4ad-4985-4c70-901d-5699dbf2cce6,0x800,0xff000)/File(\EFI\NixOS-boot\grubx64.efi)
Boot0010  Setup FvFile(721c8b66-426c-4e86-8e99-3457c46ab0b9)
Boot0011  Boot Menu     FvFile(126a762d-5758-4fca-8531-201a7f57f850)
Boot0012  Diagnostic Splash Screen      FvFile(a7d8d9a6-6ab0-4aeb-ad9d-163e59a7a380)
Boot0013  Lenovo Diagnostics    FvFile(3f7e615b-0d45-4f80-88dc-26b234958560)
Boot0014  Regulatory Information        FvFile(478c92a0-2622-42b7-a65d-5894169e4d24)
Boot0015  Startup Interrupt Menu        FvFile(f46ee6f4-4785-43a3-923d-7f786c3c8479)
Boot0016  Rescue and Recovery   FvFile(665d3f60-ad3e-4cad-8e26-db46eee9f1b5)
Boot0017  MEBx Hot Key  FvFile(ac6fd56a-3d41-4efd-a1b9-870293811a28)
Boot0018* USB CD        VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,86701296aa5a7848b66cd49dd3ba6a55)
Boot0019* USB FDD       VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,6ff015a28830b543a8b8641009461e49)
Boot001A* NVMe0 VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,001c199932d94c4eae9aa0b6e98eb8a400)
Boot001B  ATA HDD0      VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,91af625956449f41a7b91f4f892ab0f601)
Boot001C* USB HDD       VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,33e821aaaf33bc4789bd419f88c50803)
Boot001D  PCI LAN       VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,78a84aaf2b2afc4ea79cf5cc8f3d3803)
Boot001E  Other CD      VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,aea2090adfde214e8b3a5e471856a35406)
Boot001F  Other HDD     VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,91af625956449f41a7b91f4f892ab0f606)
Boot0020* USBR BOOT CDROM       PciRoot(0x0)/Pci(0x14,0x0)/USB(11,1)
Boot0021* USBR BOOT Floppy      PciRoot(0x0)/Pci(0x14,0x0)/USB(11,0)
Boot0022* ATA HDD       VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,91af625956449f41a7b91f4f892ab0f6)
Boot0023* ATAPI CD      VenMsg(bc7838d2-0f82-4d60-8316-c068ee79d25b,aea2090adfde214e8b3a5e471856a354)

[root@fnord:/]#