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1# External Bootloader Backends {#sec-bootloader-external}
2
3NixOS has support for several bootloader backends by default: systemd-boot, grub, uboot, etc.
4The built-in bootloader backend support is generic and supports most use cases.
5Some users may prefer to create advanced workflows around managing the bootloader and bootable entries.
6
7You can replace the built-in bootloader support with your own tooling using the "external" bootloader option.
8
9Imagine you have created a new package called FooBoot.
10FooBoot provides a program at `${pkgs.fooboot}/bin/fooboot-install` which takes the system closure's path as its only argument and configures the system's bootloader.
11
12You can enable FooBoot like this:
13
14```nix
15{ pkgs, ... }: {
16 boot.loader.external = {
17 enable = true;
18 installHook = "${pkgs.fooboot}/bin/fooboot-install";
19 };
20}
21```
22
23## Developing Custom Bootloader Backends {#sec-bootloader-external-developing}
24
25Bootloaders should use [RFC-0125](https://github.com/NixOS/rfcs/pull/125)'s Bootspec format and synthesis tools to identify the key properties for bootable system generations.
26