NixOS on ARM

From NixOS Wiki
Revision as of 09:33, 23 October 2018 by imported>Mbrock (Add note about the cma kernel parameter)

ARM support for NixOS is a work-in-progress, but is progressing quickly.

The support varies depending on the architecture and the specific boards. The way the ARM integration is built into NixOS is by making generic builds the first-class citizens; as soon as there is upstream support for the board in the kernel and the bootloader, NixOS should work once updated to these versions. It is still possible, when needed, to build and use a customised bootloader and kernel for specific boards[reference needed]. At this moment in time (early 2018) only AArch64 is planned for full support upstream. Though, neither armv6l or armv7l are being ignored, fixes are worked on and approved as needed; what's missing is support and upstream builds being maintained in binary form.

Supported devices

Upstream (NixOS) supported devices

NixOS has support for these boards using AArch64 architecture on the nixpkgs-unstable and nixpkgs-18.03 channel.

Manufacturer Board SoC ISA CPU RAM Storage
Raspberry Pi Foundation Raspberry Pi 3 Broadcom BCM2837 AArch64 / ARMv7 4× Cortex-A53 @ 1.2 GHz 1 GB SD/microSD

Community supported devices

The installation images by @dezgeg should work on the following devices; follow the links for more details, like installation instructions and device-specific notes.

Manufacturer Board SoC ISA CPU RAM Storage
ASUS Tinker Board Rockchip RK3288 ARMv7 4× Cortex-A17 2 GB microSD
Banana Pi Banana Pi Allwinner A20 ARMv7 2× Cortex-A7 1 GB SD, SATA
BeagleBoard.org BeagleBone Black TI AM335x ARMv7 1× Cortex-A8 @ 1 GHz 512 MB 4 GB eMMC, microSD
Hardkernel ODROID-C2 Amlogic S905 AArch64 4 × Cortex-A53 @ 1.5GHz 2 GB eMMC, microSD
Linksprite pcDuino3 Nano Allwinner A20 ARMv7 2× Cortex-A7 @ 1 GHz 1 GB 4 GB NAND, microSD, SATA
NVIDIA Jetson TK1 Tegra K1/T124 ARMv7 4× Cortex-A15 @ 2.3 GHz 2 GB 16 GB eMMC, SD, SATA
Orange Pi Orange Pi PC Allwinner H3 ARMv7 4× Cortex-A7 @ 1.6 GHz 1 GB SD/microSD
Orange Pi Orange Pi Zero Plus2 (H5) Allwinner H5 AArch64 4× Cortex-A53 @ 1.2 GHz 1 GB SD/microSD + 8GB eMMC
PINE64 PINE A64-LTS Allwinner R18 AArch64 4× Cortex-A53 @ ? GHz 2 GB SD/microSD & eMMC
Raspberry Pi Foundation Raspberry Pi Broadcom BCM2835 ARMv6 1× ARM1176 @ 700 MHz 256 MB / 512 MB SD/microSD
Raspberry Pi Foundation Raspberry Pi 2 Broadcom BCM2836 ARMv7 4× Cortex-A7 @ 900 MHz 1 GB SD/microSD
Raspberry Pi Foundation Raspberry Pi 3 Broadcom BCM2837 AArch64 / ARMv7 4× Cortex-A53 @ 1.2 GHz 1 GB SD/microSD
Toshiba AC100 (mini laptop) Tegra 2 250 (T20) ARMv7 2× Cortex-A9 @ 1 GHz 512 MB 8­­–32 GB eMMC, SD
Wandboard Wandboard Solo/Dual/Quad Freescale i.MX6 ARMv7 1×/2×/4× Cortex-A9 @ 1000 MHz 512 MB / 1 GB / 2 GB microSD, SATA

Special Devices

It is possible to emulate an ARM platform with QEMU.

Manufacturer Board SoC ISA CPU RAM Storage
QEMU QEMU — ARMv7 up to 8 up to 2 GB Anything QEMU supports

Installation

Getting the installer

The most current installation images and miscellaneous boot files for ARM devices are currently built maintained and hosted by @dezgeg at http://nixos-arm.dezgeg.me/installer. Generic usage is described in this page, and board-specific instructions when needed are described on their page.

Installation steps

The installation images come in two flavors: sd-image-armv6l-linux.img is built for the ARMv6 architecture and it comes with the Raspberry Pi kernel. sd-image-armv7l-linux.img is built for the ARMv7 architecture and comes with the mainline multiplatform ARMv7 kernel (multi_v7_defconfig). Make sure you download the correct image for your board!

The .img files can be directly written to a microSD/SD card (minimal recommended size: 4 GB) using dd. 

sudo dd if=sd-image-armv7l-linux.img of=/dev/sdX

Replace /dev/sdX with the path to your SD card device.

The base images are configured to boot up with a serial TTY ( RX/TX UART ) @ 115200 Baud. That way you not necessarily have to have a HDMI Display and keyboard.

Continue with #NixOS installation & configuration.

Binary cache

AArch64

Thanks to @grahamc and Packet the official NixOS Hydra builds a full set of binaries (available on https://cache.nixos.org) for the AArch64 architecture on the nixpkgs-unstable channel. Starting with the 18.03 release the official Hydra instance will also build the stable channel .


armv6l and armv7l

A binary cache, containing a subset of the nixos-unstable channel, is hosted at http://nixos-arm.dezgeg.me/channel (signed with key nixos-arm.dezgeg.me-1:xBaUKS3n17BZPKeyxL4JfbTqECsT+ysbDJz29kLFRW0=%).

Additional caches

Board-specific installation notes

Depending on the board, some additional preparation steps might be needed to make the SD card bootable on your device. All of the board-specific installation notes are now found on their respective pages.

Enable UART

If you try to use UART to log on NixOS, you might hang on the line "Starting kernel ...". To enable UART, you will need to add at the end of the line that contains loglevel4 in the file /extlinux/extlinux.conf the text: 

/extlinux/extlinux.conf

    console=ttyAMA0,115200n8
/extlinux/extlinux.conf

    console=ttyS0,115200n8

The actual device (ttyAMA0, ttyS0) will depend on the hardware.

NixOS installation & configuration

The installation image is actually a MBR partition table plus two partitions; a FAT32 /boot and a ext4 root filesystem. The image is designed such that it's possible to directly reuse the SD image's partition layout and "install" NixOS on the very same SD card by simply replacing the default configuration.nix and running nixos-rebuild. Using this installation method is strongly recommended, though if you know exactly what you're doing and how U-Boot on your board works, you can use nixos-install as usual. To help with the SD card installation method, the boot scripts on the image automatically resize the rootfs partition to fit the SD card on the first boot.

Use this as a template: 

/etc/nixos/configuration.nix

{ config, pkgs, lib, ... }:
{
  # NixOS wants to enable GRUB by default
  boot.loader.grub.enable = false;
  # Enables the generation of /boot/extlinux/extlinux.conf
  boot.loader.generic-extlinux-compatible.enable = true;
 
  # !!! If your board is a Raspberry Pi 1, select this:
  boot.kernelPackages = pkgs.linuxPackages_rpi;
  # !!! Otherwise (even if you have a Raspberry Pi 2 or 3), pick this:
  boot.kernelPackages = pkgs.linuxPackages_latest;
  
  # !!! This is only for ARMv6 / ARMv7. Don't enable this on AArch64, cache.nixos.org works there.
  nix.binaryCaches = lib.mkForce [ "http://nixos-arm.dezgeg.me/channel" ];
  nix.binaryCachePublicKeys = [ "nixos-arm.dezgeg.me-1:xBaUKS3n17BZPKeyxL4JfbTqECsT+ysbDJz29kLFRW0=%" ];

  # !!! Needed for the virtual console to work on the RPi 3, as the default of 16M doesn't seem to be enough.
  # If X.org behaves weirdly (I only saw the cursor) then try increasing this to 256M.
  boot.kernelParams = ["cma=32M"];
    
  # File systems configuration for using the installer's partition layout
  fileSystems = {
    "/boot" = {
      device = "/dev/disk/by-label/NIXOS_BOOT";
      fsType = "vfat";
    };
    "/" = {
      device = "/dev/disk/by-label/NIXOS_SD";
      fsType = "ext4";
    };
  };
    
  # !!! Adding a swap file is optional, but strongly recommended!
  # swapDevices = [ { device = "/swapfile"; size = 1024; } ];
}

Note: the default configuration.nix will contain something like imports = [ <nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix> ]; do not include that in your final installation or you will experience interesting problems. It is only for building the installation image!

First rebuild on ARMv6 and ARMv7

To make the unsupported ARM experience slightly less painful, the config template adds nixos-arm.dezgeg.me as a binary cache, which contains a small subset of packages on the unstable channel (though a caution for US users: the server hosting them is physically located in Finland). Note that the binary cache isn't enabled on the prebuilt images, so enable it via the command line when building for the first time: 

nixos-rebuild switch --fast --option binary-caches http://nixos-arm.dezgeg.me/channel --option binary-cache-public-keys nixos-arm.dezgeg.me-1:xBaUKS3n17BZPKeyxL4JfbTqECsT+ysbDJz29kLFRW0=%

Resizing the boot partition

Note: The instructions as they are were tested on the Raspberry Pi 3
Warning: Platforms needing a secondary boot loader before the boot partition, (when using dd to add u-boot, MLO or SPL) will need to take in consideration where the original /boot partition starts.

It is possible that you run out of disk space on the boot partition after some system upgrades. To resize the boot partition:

  • (If not already done, boot once to trigger the initial partition resizing)
  • Backup the files currently stored in the boot partition
  • Repartition and make sure to delete and then recreate the boot partition (fat32, primary, label: NIXOS_BOOT)
  • Copy the files from the backup back to the new boot partition

Disable use of /boot partition

Note: The instructions as they are were tested on the PINE A64-LTS, though were written for the Raspberry Pi 3

The /boot partition is quite small on the NixOS on ARM images. This means that few generations can be kept, and nixos-rebuild can often fail due to lack of space.

Here are quick instructions to disable use of the (small) /boot partition. The disk used in the following example is /dev/mmcblk1 which may differ depending on use of SD card and the particular device. 

# umount /boot

Comment out the fileSystems."/boot" entry from configuration.nix 

# $EDITOR /etc/configuration.nix

Use fdisk or cfdisk to remove the bootable flag from the FAT32 partition, and set it for the ext4 partition 

# fdisk -l /dev/mmcblk1
Disk /dev/mmcblk1: 58.2 GiB, 62537072640 bytes, 122142720 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x2178694e

Device         Boot  Start       End   Sectors  Size Id Type
/dev/mmcblk1p1 *     16384    262143    245760  120M  b W95 FAT32
/dev/mmcblk1p2      262144 122142567 121880424 58.1G 83 Linux

# echo -e 'a\n1\na\n2\nw' | fdisk /dev/mmcblk1

Welcome to fdisk (util-linux 2.31.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): Partition number (1,2, default 2): 
The bootable flag on partition 1 is disabled now.

Command (m for help): Partition number (1,2, default 2): 
The bootable flag on partition 2 is enabled now.

Command (m for help): The partition table has been altered.
Syncing disks.


# fdisk -l /dev/mmcblk1
Disk /dev/mmcblk1: 58.2 GiB, 62537072640 bytes, 122142720 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x2178694e

Device         Boot  Start       End   Sectors  Size Id Type
/dev/mmcblk1p1       16384    262143    245760  120M  b W95 FAT32
/dev/mmcblk1p2 *    262144 122142567 121880424 58.1G 83 Linux

Then rebuild the system. 

$ nixos-rebuild switch

You may want to verify the presence of the /boot/extlinux/extlinux.conf file.

Details about the boot process

On NixOS, all ARM boards use the popular U-Boot as the bootloader and U-Boot's Generic Distro Configuration Concept as the mechanism to communicate boot information (such as path to kernel zImage, initrd, DTB, command line arguments). For a quick TL;DR about the generic distro configuration support: U-Boot is scripted to scan all attached storage devices & partitions and look for a file named /extlinux/extlinux.conf or /boot/extlinux/extlinux.conf (which will be generated by NixOS, just like /boot/grub/grub.cfg is generated on PCs).

U-Boot also provides an interactive shell and the generation selection menu (just like GRUB). However, support for input or display devices varies greatly, depending on the board. Details for what the boards support in relationship to the boot process are detailed in their respective pages.

Porting NixOS to new boards

The easy way

(if you're lucky)

If your board is an ARMv7 board supported by multi_v7_defconfig and you have access to U-Boot on the board, getting sd-image-armv7l-linux.img to boot is the easiest option:

  • If you're lucky and your U-Boot build comes with the extlinux.conf support built in, the image boots out-of-the-box. This is the case for all (upstream) Allwinner and Tegra U-Boots, for instance.
  • Otherwise, you can get the boot information (path to kernel zImage, initrd, DTB, command line arguments) by extracting extlinux.conf from the boot partition of the image, and then attempt to boot it via the U-Boot shell, or some other mechanism that your board's distro uses (e.g. uEnv.txt).

Building u-boot from your NixOS PC

Assuming

  • Your board is supported upstream by u-boot or there is a recent enough fork with extlinux.conf support.
  • You do not have nix setup on an ARM device
  • Your nix isn't setup for cross-compilation

It is still possible to build u-boot using tools provided by NixOS.

In the following terminal session, replace orangepi_pc_defconfig with the appropriate board from the configs folder of u-boot. 

$ nix-shell -E 'with import <nixpkgs> {}; stdenv.mkDerivation { name = "arm-shell"; buildInputs = [git gnumake gcc gcc-arm-embedded dtc]; }'
$ git clone git://git.denx.de/u-boot.git
$ cd u-boot
# We're checking out a version from before the use of `binman`.
# The dtc package is 1.4.2, which does not include `pylibftd`.
# Furthermore, I do not know how to package the library so it would be
# available in the python interpreter, making binman happy.
$ git checkout v2017.03
$ make -j4 CROSS_COMPILE=arm-none-eabi- orangepi_pc_defconfig
$ make -j4 CROSS_COMPILE=arm-none-eabi-

The name of the final file will change depending on the board. For this specific build, and most Allwinner builds, the file will be named u-boot-sunxi-with-spl.bin.

You can flash this file to boot device with 

 dd if=u-boot-sunxi-with-spl.bin of=/dev/sdX bs=1024 seek=8

Note: This mailing list contains a patch which may help some builds: https://lists.denx.de/pipermail/u-boot/2016-December/275664.html

The hard way

Alternatively/if all else fails, you can do it the hard way and bootstrap NixOS from an existing ARM Linux installation.

Contributing new boards to nixpkgs

  • Add a new derivation for your board's U-Boot configuration, see for example ubootJetsonTK1 in all-packages.nix.
  • If your board's U-Boot configuration doesn't use the extlinux.conf format by default, create a patch to enable it. Some C hacking skills & U-Boot knowledge might be required. For some pointers, see this patch to enable it on the Versatile Express.
  • Make a pull request, also containing the board-specific instructions. Ping @dezgeg for review and for building & hosting the U-Boots at http://nixos-arm.dezgeg.me/installer.

Support

All ARM platforms are experimental. Only AArch64 platforms are currently being worked on for eventual support from NixOS.

There is a dedicated IRC Channel for the upstream effort on freenode, #nixos-aarch64.

Resources

Subpages

The following is a list of all sub-pages of the NixOS on ARM topic.

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