The current FAT32 partition is kept as it is required for the Raspberry
Pi family of hardware. It is where the firmware is kept.
The partition is kept bootable, and the boot files kept in there until
the following commits, to keep all commits of this series individually
bootable.
Turns out all variants of start.elf and fixup.dat are needed (depending
on what's in config.txt). I was under the mistaken impression that you
were supposed to rename one of the variants to switch using them, but
nope.
Since commits 89e9837 and 5b8dae8 the manual no longer depends on
evaluation of any packages from nixpkgs, so all errors of the form
"Package 'foo' is not supported on 'armv7l-linux'" are gone.
The resulting image can be copied to a SD card with `dd` and is directly
bootable by a suitably configured U-Boot. Though depending on the board, some
extra steps are required for copying U-Boot itself to the SD card.
Inside the image is a partition table, with a FAT32 /boot and a normal
writable EXT4 rootfs. It's possible to directly reuse the SD image's
partition layout and "install" NixOS on the same SD card by replacing
the default configuration.nix and nixos-rebuild, and actually is the
preferred way to use these images. To assist in this installation
method, the boot scripts on the image automatically resize the rootfs
partition to fit the SD card on the first boot.
The SD images come in two flavors; one for the ARMv6 Raspberry Pi,
and one multiplatform image for all the boards supported by the
mainline kernel's multi_v7_defconfig config target. At the moment, these
have been tested on:
- Raspberry Pi Model B (512MB model)
- NVIDIA Jetson TK1
- Linksprite pcDuino3 Nano
To build, run:
nix-build '<nixpkgs/nixos>' -A config.system.build.sdImage \
-I nixos-config='<nixpkgs/nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix>'
