NixOS on ARM/Raspberry Pi 4: Difference between revisions

Raspberry Pi 4 Family
	(Image not available)
Manufacturer	Raspberry Pi Foundation
Architecture	AArch64
Bootloader	Custom or U-Boot
Boot order	Configurable; SD, USB, Netboot
Maintainer
Raspberry Pi 4B
SoC	BCM2711

← Older edit Newer edit →

VisualWikitext

Revision as of 13:16, 13 January 2023

← Back to NixOS on ARM

The Raspberry Pi family of devices is a series of single-board computers made by the Raspberry Pi Foundation. They are all based on Broadcom System-on-a-chip (SoCs).

Status

The Raspberry Pi 4 Family is only supported as AArch64. Use as armv7 is community supported.

Board-specific installation notes

First follow the generic installation steps to get the installer image and install using the installation and configuration steps.

The Raspberry Pi 4B works with the generic SD image.

Sample instructions for installing NixOS on a Raspberry Pi are available at nix.dev.

Warning: Note that the Raspberry Pi 4 has two HDMI outputs, and apparently sometimes the user prompt for the console/TTY is displayed on HDMI 1 while the boot process is displayed on HDMI 0 (this may even be the case with the official (non NixOs) non-graphical lite image). So if after the message "Welcome on NixOs" at the end of phase 2 your screen goes black/disconnects, try to use the other HDMI port. See the related bug here.

Configuration

This article or section is out of date.

Reason: These instructions were written when the generic image did not work. Using the vendor kernel may be desirable under some conditions^[which?] (Discuss in Talk:NixOS on ARM/Raspberry Pi 4)
Once the page has been updated this notice can be removed.

Using nixos-generate-config will not generate the required minimal configuration.

For better GPU Support, remember to add the nixos-hardware channel: nixos-hardware https://github.com/NixOS/nixos-hardware/archive/master.tar.gz

/etc/nixos/configuration.nix

{ config, pkgs, lib, ... }:

{
 # This configuration worked on 09-03-2021 nixos-unstable @ commit 102eb68ceec
 # The image used https://hydra.nixos.org/build/134720986

  boot = {
    kernelPackages = pkgs.linuxPackages_rpi4;
    tmpOnTmpfs = true;
    initrd.availableKernelModules = [ "usbhid" "usb_storage" ];
    # ttyAMA0 is the serial console broken out to the GPIO
    kernelParams = [
        "8250.nr_uarts=1"
        "console=ttyAMA0,115200"
        "console=tty1"
        # A lot GUI programs need this, nearly all wayland applications
        "cma=128M"
    ];
  };

  boot.loader.raspberryPi = {
    enable = true;
    version = 4;
  };
  boot.loader.grub.enable = false;

  # Required for the Wireless firmware
  hardware.enableRedistributableFirmware = true;

  networking = {
    hostName = "nixos-raspi-4"; # Define your hostname.
    networkmanager = {
      enable = true;
    };
  };

  nix = {
    autoOptimiseStore = true;
    gc = {
      automatic = true;
      dates = "weekly";
      options = "--delete-older-than 30d";
    };
    # Free up to 1GiB whenever there is less than 100MiB left.
    extraOptions = ''
      min-free = ${toString (100 * 1024 * 1024)}
      max-free = ${toString (1024 * 1024 * 1024)}
    '';
  };
  system.stateVersion = "20.09";
}

USB boot

For USB booting to work properly, a firmware update might be needed:

 $ nix-shell -p raspberrypi-eeprom
 $ rpi-eeprom-update -d -a

Now reboot the device so it can update the firmware from boot partition.

When running from USB device without SD card present, kernel spams log about missing SD card, workaround for this is to set:

This article or section is out of date.

Reason: This will only work when not using U-Boot. Configuring through an overlay will be required. (Discuss in Talk:NixOS on ARM/Raspberry Pi 4)
Once the page has been updated this notice can be removed.

/etc/nixos/configuration.nix

{
  boot.loader.raspberryPi.firmwareConfig = "dtparam=sd_poll_once=on";
}

GPU support

The following configuration samples are built on the assumption that they are added to an already working configuration. They are not complete configurations.

Without GPU

/etc/nixos/configuration.nix

{
  services.xserver = {
    enable = true;
    displayManager.lightdm.enable = true;
    desktopManager.gnome3.enable = true;
    videoDrivers = [ "fbdev" ];
  };
}

With GPU

In nixos-hardware#261 a new option has been added to use the fkms-3d overlay. This will only work with the vendor kernel.

/etc/nixos/configuration.nix

{ pkgs, ... }:

{
  imports = [
    .../nixos-hardware/raspberry-pi/4
  ];

  hardware.raspberry-pi."4".fkms-3d.enable = true;

  services.xserver = {
    enable = true;
    displayManager.lightdm.enable = true;
    desktopManager.gnome3.enable = true;
  };
}

Tools

The raspberry tools are available in the libraspberrypi package and include commands like vcgencmd to measure temperature and CPU frequency.

Audio

This article or section is out of date.

Reason: An equivalent change that works with U-Boot through hardware.deviceTree is needed. (Discuss in Talk:NixOS on ARM/Raspberry Pi 4)
Once the page has been updated this notice can be removed.

In addition to the usual config, you will need to enable audio support explicitly in the firmwareConfig.

/etc/nixos/configuration.nix

  sound.enable = true;
  hardware.pulseaudio.enable = true;

  boot.loader.raspberryPi.firmwareConfig = ''
    dtparam=audio=on
  '';

Using GPIO pins as non root

By default, the GPIO pins are enable, but can only be accessed by the root user. This can be address by adding a udev rule to your configuration that changes the owner ship of /dev/gpiomem and the other required devices.

The following code adds a group gpio and adds the user mygpiouser to that group. You probably want to put your own user name here.

The extraRules change the owner of gpiomem and all other files needed for GPIO to work to root:gpio and changes the permissions to 0660. Therefore, the root user and anyone in the gpio group can now access the GPIO pins.

  # Create gpio group
  users.groups.gpio = {};

  # Change permissions gpio devices
  services.udev.extraRules = ''
    SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio",MODE="0660"
    SUBSYSTEM=="gpio", KERNEL=="gpiochip*", ACTION=="add", RUN+="${pkgs.bash}/bin/bash -c 'chown root:gpio  /sys/class/gpio/export /sys/class/gpio/unexport ; chmod 220 /sys/class/gpio/export /sys/class/gpio/unexport'"
    SUBSYSTEM=="gpio", KERNEL=="gpio*", ACTION=="add",RUN+="${pkgs.bash}/bin/bash -c 'chown root:gpio /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value ; chmod 660 /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value'"
  '';

  # Add user to group
  users = {
    users.mygpiouser = {
      extraGroups = [ "gpio" ... ];
      ....
    };
  };

HDMI-CEC

A few bits and pieces for using HDMI-CEC on the Pi4:

/etc/nixos/configuration.nix

{ pkgs, ... }:

{
  # an overlay to enable raspberrypi support in libcec, and thus cec-client
  nixpkgs.overlays = [
    # nixos-22.05
    # (self: super: { libcec = super.libcec.override { inherit (self) libraspberrypi; }; })
    # nixos-22.11
    (self: super: { libcec = super.libcec.override { withLibraspberrypi = true; }; })
  ];

  # install libcec, which includes cec-client (requires root or "video" group, see udev rule below)
  # scan for devices: `echo 'scan' | cec-client -s -d 1`
  # set pi as active source: `echo 'as' | cec-client -s -d 1`
  environment.systemPackages = with pkgs; [
    libcec
  ];

  services.udev.extraRules = ''
    # allow access to raspi cec device for video group (and optionally register it as a systemd device, used below)
    SUBSYSTEM=="vchiq", GROUP="video", MODE="0660", TAG+="systemd", ENV{SYSTEMD_ALIAS}="/dev/vchiq"
  '';

  # optional: attach a persisted cec-client to `/run/cec.fifo`, to avoid the CEC ~1s startup delay per command
  # scan for devices: `echo 'scan' &gt; /run/cec.fifo ; journalctl -u cec-client.service`
  # set pi as active source: `echo 'as' &gt; /run/cec.fifo`
  systemd.sockets."cec-client" = {
    after = [ "dev-vchiq.device" ];
    bindsTo = [ "dev-vchiq.device" ];
    wantedBy = [ "sockets.target" ];
    socketConfig = {
      ListenFIFO = "/run/cec.fifo";
      SocketGroup = "video";
      SocketMode = "0660";
    };
  };
  systemd.services."cec-client" = {
    after = [ "dev-vchiq.device" ];
    bindsTo = [ "dev-vchiq.device" ];
    wantedBy = [ "multi-user.target" ];
    serviceConfig = {
      ExecStart = ''${pkgs.libcec}/bin/cec-client -d 1'';
      ExecStop = ''/bin/sh -c "echo q &gt; /run/cec.fifo"'';
      StandardInput = "socket";
      StandardOutput = "journal";
      Restart="no";
  };
}

Notes about the boot process

Unless using an extremely early WIP image, the Raspberry Pi 4B boots using the U-Boot platform firmware.

Updating U-Boot/Firmware

 
$ nix-shell -p raspberrypi-eeprom
$ sudo mount /dev/disk/by-label/FIRMWARE /mnt
$ sudo BOOTFS=/mnt FIRMWARE_RELEASE_STATUS=stable rpi-eeprom-update -d -a

source

Troubleshooting

=== Power issues ===non-functionalnon-functnon-functionalionalnon-functional

The Raspberry Pi 4B is as power-hungry, if not more, as its predecessors. It is important to have a sufficient enough power supply or weirdness may happen. Weirdness may include:

Lightning bolt icon on HDMI output "breaking" the display.
Screen switching back to u-boot text
- Fixable temporarily when power is sufficient by switching VT (alt+F2 / alt+F1)
Random hangs

Note: A properly rated USB power supply, AND a good cable are necessary. The cable has to be short enough to not incur power losses through the length. Do note that thin and cheap cables usually have thinner copper wires, which in turn accentuates power losses.

Note that the Type-C USB receptacle for the Raspberry Pi 4B does not implement Power Delivery (USB PD). This means that it is limited to whatever the power supply will provide when not negotiating power, which is most likely 5V at some undetermined power level.

Audio not playing and Bluetooth: no controller available

On the Raspberry Pi kernel, the jack may never play audio, and no Bluetooth devices may ever be found. To get this to work, it is recommended to switch to the mainline kernel. See nixpkgs#123725 for more info.

@@ Line 180: / Line 180: @@
 </nowiki>}}
-=== Gpio ===
+=== Using GPIO pins as non root ===
-Add gpio group and change permission for all users in new gpio group.
-Now all users in gpio group have access to /dev/gpiomem and to gpio pins via sysfs.
+By default, the GPIO pins are enable, but can only be accessed by the root user.
+This can be address by adding a [https://wiki.archlinux.org/title/Udev udev] rule to your configuration that changes the owner ship of <code>/dev/gpiomem</code> and the other required devices.
-{{file|/etc/nixos/configuration.nix|nix|<nowiki>
+The following code adds a group <code>gpio</code> and adds the user <code>mygpiouser</code> to that group.
-   # add gpio group
+You probably want to put your own user name here.
+The <code>extraRules</code> change the owner of <code>gpiomem</code> and all other files needed for GPIO to work to <code>root:gpio</code> and changes the permissions to <code>0660</code>.
+Therefore, the root user and anyone in the gpio group can now access the GPIO pins.
+<syntaxHighlight lang="nix">
+   # Create gpio group
    users.groups.gpio = {};
-   # udev rule for gpio
+   # Change permissions gpio devices
    services.udev.extraRules = ''
      SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio",MODE="0660"
@@ Line 196: / Line 202: @@
    '';
-   # add user with gpio group
+   # Add user to group
    users = {
-    mutableUsers = false;
      users.mygpiouser = {
-      isNormalUser = true;
+       extraGroups = [ "gpio" ... ];
-      password = "mygpiouserpasswd";
+      ....
-       extraGroups = [ "wheel" "gpio" ];
      };
    };
+</syntaxHighlight>
-</nowiki>}}
 === HDMI-CEC ===