A Minimal Buildroot config for the Raspberry Pi Zero, inspired by Minimal Raspberry Pi 3, but with most features usable out of the box. This build should serve as a good starting point for any headless pi zero embedded projects.
Kernel boot time measures approximately 2 seconds when the quiet parameter is added to the pi kernel's cmdline.txt arguments. Without changing the start.elf bootloader to the cutdown version, the total boot time from initial power on is about 5-6 seconds. Overclocking the SD card, if you have a class 10 or UHS 1 card, should yield a bit of a boost. Shaved off about 0.5-1 second on my board. Additional gains can come by trimming unused kernel features as well. An initramfs-only image and/or embedded device tree may also improve overall boot times.
See below section for limitations.
This repository uses git submodules to manage the buildroot version used by this project. As such, you will want to clone this repository using git clone --recursive or manually initialize the buildroot submodule yourself. This submodule is configured to be the buildroot directory in this repository.
After cloning the repository (and initializing the buildroot submodule if cloning without --recursive), navigate to the build_workdir directory and run ./configure. This sets up the buildroot external tree. From there, run any buildroot commands from the build_workdir directory to keep a clean external tree setup.
If you plan to use the camera port, you will need to modify the buildroot config to produce the start_x.elf bootloader/firmware file.
Networking is disabled in the kernel config. Since standard pi zeros do not have wireless, this just added extra time to the boot. If you are using an external network card, you will need to re-enable networking in the kernel.
The current busybox setup still leaves in place a network service startup script that will fail quickly due to networking being removed from the kernel. I'm sure I'll get around to cleaning that up sometime soon. If it's an issue, just delete the script from the /etc/init.d folder in the generated image.
This configuration uses the musl c library. It was chosen due to its very diminuitive size and its growing use (ex. standard clib in Alpine linux). If you have a program that relies on glibc quirks or want to use uclibc, change the clib in the buildroot config.